AbstractDateField.formatDate() to be abstract (#10186)

* AbstractDateField.formatDate to be abstract

Remove invalidDateString paramter, as it can be deduced

* Fix test

* Remove AbstractDateField.getResolutionVariable

VAbstractTextualDate: rename updateDateVariables() to updateBufferedResolutions()

* Revert to use fixed value of MONDAY.

* release notes

* updateAndSendBufferedValues()

* Missed call to updateAndSendBufferedValues();

* release note

16 files changed, 272 insertions, 308 deletions

diff --git a/all/src/main/templates/release-notes.html b/all/src/main/templates/release-notes.html
index f3852f2671..b16ac14949 100644
--- a/all/src/main/templates/release-notes.html
+++ b/all/src/main/templates/release-notes.html
@@ -124,6 +124,8 @@
         <li><tt>SharedState</tt> field <tt>registeredEventListeners</tt> is a <tt>Map</tt> instead of <tt>Set</tt>.</li>
         <li>The client side <tt>SelectionModel</tt> interface has a new method <tt>isMultiSelectionAllowed</tt>.</li>
         <li><tt>AbstractDateField</tt> is not a <tt>LegacyComponent</tt> anymore.</li>
+        <li><tt>AbstractDateField</tt>.<tt>formatDate</tt> is now abstract.</li>
+        <li><tt>VAbstractTextualDate</tt>.<tt>updateDateVariables()</tt> is now <tt>updateBufferedResolutions()</tt> and <tt>updateAndSendBufferedValues()</tt>.</li>
 
         <h2>For incompatible or behavior-altering changes in 8.1, please see <a href="https://vaadin.com/download/release/8.1/8.1.0/release-notes.html#incompatible">8.1 release notes</a></h2>
         
diff --git a/client/src/main/java/com/vaadin/client/DateTimeService.java b/client/src/main/java/com/vaadin/client/DateTimeService.java
index 7367d686b6..fb4aaf130d 100644
--- a/client/src/main/java/com/vaadin/client/DateTimeService.java
+++ b/client/src/main/java/com/vaadin/client/DateTimeService.java
@@ -602,7 +602,6 @@ public class DateTimeService {
         }
 
         return date;
-
     }
 
     private static Logger getLogger() {
diff --git a/client/src/main/java/com/vaadin/client/LocaleService.java b/client/src/main/java/com/vaadin/client/LocaleService.java
index 88d07ee836..39c77d4697 100644
--- a/client/src/main/java/com/vaadin/client/LocaleService.java
+++ b/client/src/main/java/com/vaadin/client/LocaleService.java
@@ -65,81 +65,72 @@ public class LocaleService {
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).monthNames;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static String[] getShortMonthNames(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).shortMonthNames;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static String[] getDayNames(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).dayNames;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static String[] getShortDayNames(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).shortDayNames;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static int getFirstDayOfWeek(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).firstDayOfWeek;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static String getDateFormat(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).dateFormat;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static boolean isTwelveHourClock(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).twelveHourClock;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static String getClockDelimiter(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return cache.get(locale).hourMinuteDelimiter;
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static String[] getAmPmStrings(String locale)
             throws LocaleNotLoadedException {
         if (cache.containsKey(locale)) {
             return new String[] { cache.get(locale).am, cache.get(locale).pm };
-        } else {
-            throw new LocaleNotLoadedException(locale);
         }
+        throw new LocaleNotLoadedException(locale);
     }
 
     public static void addLocales(List<LocaleData> localeDatas) {
diff --git a/client/src/main/java/com/vaadin/client/ui/AbstractConnector.java b/client/src/main/java/com/vaadin/client/ui/AbstractConnector.java
index 849f977b53..7f58bf35a3 100644
--- a/client/src/main/java/com/vaadin/client/ui/AbstractConnector.java
+++ b/client/src/main/java/com/vaadin/client/ui/AbstractConnector.java
@@ -336,9 +336,7 @@ public abstract class AbstractConnector
                         OnStateChangeMethod method = propertyMethods.get(j);
 
                         if (invokedMethods.add(method)) {
-
                             method.invoke(stateChangeEvent);
-
                         }
                     }
                 }
@@ -361,7 +359,6 @@ public abstract class AbstractConnector
             VConsole.log(
                     "Unregistered connector " + Util.getConnectorString(this));
         }
-
     }
 
     /**
@@ -447,11 +444,7 @@ public abstract class AbstractConnector
             return false;
         }
 
-        if (getParent() == null) {
-            return true;
-        } else {
-            return getParent().isEnabled();
-        }
+        return getParent() == null || getParent().isEnabled();
     }
 
     @Override
@@ -474,21 +467,20 @@ public abstract class AbstractConnector
      * Gets the URL for a resource that has been added by the server-side
      * connector using
      * {@link com.vaadin.terminal.AbstractClientConnector#setResource(String, com.vaadin.terminal.Resource)}
-     * with the same key. <code>null</code> is returned if no corresponding
-     * resource is found.
+     * with the same key. {@code null} is returned if no corresponding resource
+     * is found.
      *
      * @param key
      *            a string identifying the resource.
-     * @return the resource URL as a string, or <code>null</code> if no
-     *         corresponding resource is found.
+     * @return the resource URL as a string, or {@code null} if no corresponding
+     *         resource is found.
      */
     public String getResourceUrl(String key) {
         URLReference urlReference = getState().resources.get(key);
         if (urlReference == null) {
             return null;
-        } else {
-            return urlReference.getURL();
         }
+        return urlReference.getURL();
     }
 
     /*
diff --git a/client/src/main/java/com/vaadin/client/ui/VAbstractPopupCalendar.java b/client/src/main/java/com/vaadin/client/ui/VAbstractPopupCalendar.java
index 85594484b3..c0f8413530 100644
--- a/client/src/main/java/com/vaadin/client/ui/VAbstractPopupCalendar.java
+++ b/client/src/main/java/com/vaadin/client/ui/VAbstractPopupCalendar.java
@@ -231,16 +231,15 @@ public abstract class VAbstractPopupCalendar<PANEL extends VAbstractCalendarPane
         R resolution = getCurrentResolution();
         if (currentDate == null || newDate.getTime() != currentDate.getTime()) {
             setCurrentDate((Date) newDate.clone());
-            bufferedResolutions.put(
-                    calendar.getResolution(calendar::isYear).name(),
+            bufferedResolutions.put(calendar.getResolution(calendar::isYear),
                     newDate.getYear() + 1900);
             if (!calendar.isYear(resolution)) {
                 bufferedResolutions.put(
-                        calendar.getResolution(calendar::isMonth).name(),
+                        calendar.getResolution(calendar::isMonth),
                         newDate.getMonth() + 1);
                 if (!calendar.isMonth(resolution)) {
                     bufferedResolutions.put(
-                            calendar.getResolution(calendar::isDay).name(),
+                            calendar.getResolution(calendar::isDay),
                             newDate.getDate());
                 }
             }
diff --git a/client/src/main/java/com/vaadin/client/ui/VAbstractTextualDate.java b/client/src/main/java/com/vaadin/client/ui/VAbstractTextualDate.java
index edbc863188..8206f2f862 100644
--- a/client/src/main/java/com/vaadin/client/ui/VAbstractTextualDate.java
+++ b/client/src/main/java/com/vaadin/client/ui/VAbstractTextualDate.java
@@ -121,16 +121,15 @@ public abstract class VAbstractTextualDate<R extends Enum<R>>
     protected String createFormatString() {
         if (isYear(getCurrentResolution())) {
             return "yyyy"; // force full year
-        } else {
-            try {
-                String frmString = LocaleService.getDateFormat(currentLocale);
-                return cleanFormat(frmString);
-            } catch (LocaleNotLoadedException e) {
-                // TODO should die instead? Can the component survive
-                // without format string?
-                VConsole.error(e);
-                return null;
-            }
+        }
+        try {
+            String frmString = LocaleService.getDateFormat(currentLocale);
+            return cleanFormat(frmString);
+        } catch (LocaleNotLoadedException e) {
+            // TODO should die instead? Can the component survive
+            // without format string?
+            VConsole.error(e);
+            return null;
         }
     }
 
@@ -203,7 +202,7 @@ public abstract class VAbstractTextualDate<R extends Enum<R>>
 
     /**
      * Sets the time zone for the field.
-     * 
+     *
      * @param timeZone
      *            the new time zone to use
      * @since 8.2
@@ -243,8 +242,6 @@ public abstract class VAbstractTextualDate<R extends Enum<R>>
                 VConsole.log(e);
 
                 addStyleName(getStylePrimaryName() + PARSE_ERROR_CLASSNAME);
-                // this is a hack that may eventually be removed
-                bufferedInvalidDateString = true;
                 setDate(null);
             }
         } else {
@@ -255,28 +252,40 @@ public abstract class VAbstractTextualDate<R extends Enum<R>>
 
         // always send the date string
         bufferedDateString = text.getText();
-        updateDateVariables();
+        updateAndSendBufferedValues();
+    }
+
+    /**
+     * Updates the {@link VDateField#bufferedResolutions bufferedResolutions},
+     * then {@link #sendBufferedValues() sends} the values to the server.
+     *
+     * @since
+     */
+    protected final void updateAndSendBufferedValues() {
+        updateBufferedResolutions();
+        sendBufferedValues();
     }
 
     /**
-     * Updates variables to send a response to the server.
+     * Updates {@link VDateField#bufferedResolutions bufferedResolutions} before
+     * sending a response to the server.
      * <p>
      * The method can be overridden by subclasses to provide a custom logic for
      * date variables to avoid overriding the {@link #onChange(ChangeEvent)}
      * method.
-     * 
+     *
+     * <p>
+     * Note that this method should not send the buffered values, but use
+     * {@link #updateAndSendBufferedValues()} instead
+     *
      * @since
      */
-    protected void updateDateVariables() {
-        // Update variables
-        // (only the smallest defining resolution needs to be
-        // immediate)
+    protected void updateBufferedResolutions() {
         Date currentDate = getDate();
-        bufferedResolutions.put(
-                getResolutions().filter(this::isYear).findFirst().get().name(),
-                currentDate != null ? currentDate.getYear() + 1900 : null);
-        if (isYear(getCurrentResolution())) {
-            sendBufferedValues();
+        if (currentDate != null) {
+            bufferedResolutions.put(
+                    getResolutions().filter(this::isYear).findFirst().get(),
+                    currentDate.getYear() + 1900);
         }
     }
 
@@ -432,13 +441,12 @@ public abstract class VAbstractTextualDate<R extends Enum<R>>
      * @since 8.1
      */
     public void setISODate(String isoDate) {
-        if (isoDate == null) {
-            setDate(null);
-        } else {
-            Date date = getIsoFormatter().parse(isoDate);
-            setDate(date);
+        Date date = null;
+        if (isoDate != null) {
+            date = getIsoFormatter().parse(isoDate);
         }
-        updateDateVariables();
+        setDate(date);
+        updateAndSendBufferedValues();
     }
 
     /**
@@ -454,16 +462,14 @@ public abstract class VAbstractTextualDate<R extends Enum<R>>
         Date date = getDate();
         if (date == null) {
             return null;
-        } else {
-            return getIsoFormatter().format(date);
         }
+        return getIsoFormatter().format(date);
     }
 
     private DateTimeFormat getIsoFormatter() {
         if (supportsTime()) {
             return DateTimeFormat.getFormat(ISO_DATE_TIME_PATTERN);
-        } else {
-            return DateTimeFormat.getFormat(ISO_DATE_PATTERN);
         }
+        return DateTimeFormat.getFormat(ISO_DATE_PATTERN);
     }
 }
diff --git a/client/src/main/java/com/vaadin/client/ui/VDateField.java b/client/src/main/java/com/vaadin/client/ui/VDateField.java
index 971248cee9..af1b018130 100644
--- a/client/src/main/java/com/vaadin/client/ui/VDateField.java
+++ b/client/src/main/java/com/vaadin/client/ui/VDateField.java
@@ -20,6 +20,7 @@ import java.util.Date;
 import java.util.HashMap;
 import java.util.Locale;
 import java.util.Map;
+import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import com.google.gwt.user.client.ui.FlowPanel;
@@ -66,13 +67,13 @@ public abstract class VDateField<R extends Enum<R>> extends FlowPanel
      * A temporary holder of the time units (resolutions), which would be sent
      * to the server through {@link #sendBufferedValues()}.
      * 
-     * The key is the resolution name e.g. "HOUR", "MINUTE".
+     * The key is the resolution.
      * 
      * The value can be {@code null}.
      * 
      * @since
      */
-    protected Map<String, Integer> bufferedResolutions = new HashMap<>();
+    protected Map<R, Integer> bufferedResolutions = new HashMap<>();
 
     /**
      * A temporary holder of the date string, which would be sent to the server
@@ -83,14 +84,6 @@ public abstract class VDateField<R extends Enum<R>> extends FlowPanel
     protected String bufferedDateString;
 
     /**
-     * A temporary holder of whether the date string was invalid or not, which
-     * would be sent to the server through {@link #sendBufferedValues()}.
-     * 
-     * @since
-     */
-    protected boolean bufferedInvalidDateString;
-
-    /**
      * The date that is displayed the date field before a value is selected. If
      * null, display the current date.
      */
@@ -269,16 +262,16 @@ public abstract class VDateField<R extends Enum<R>> extends FlowPanel
     }
 
     /**
-     * Sends the {@link #bufferedDateString}, {@link #bufferedInvalidDateString}
-     * and {@link #bufferedResolutions} to the server, and clears their values.
+     * Sends the {@link #bufferedDateString} and {@link #bufferedResolutions} to
+     * the server, and clears their values.
      * 
      * @since
      */
     public void sendBufferedValues() {
-        rpc.update(bufferedDateString, bufferedInvalidDateString,
-                new HashMap<>(bufferedResolutions));
+        rpc.update(bufferedDateString,
+                bufferedResolutions.entrySet().stream().collect(Collectors
+                        .toMap(e -> e.getKey().name(), e -> e.getValue())));
         bufferedDateString = null;
-        bufferedInvalidDateString = false;
         bufferedResolutions.clear();
     }
 
diff --git a/client/src/main/java/com/vaadin/client/ui/VDateFieldCalendar.java b/client/src/main/java/com/vaadin/client/ui/VDateFieldCalendar.java
index 69e6d923ce..6e727ee640 100644
--- a/client/src/main/java/com/vaadin/client/ui/VDateFieldCalendar.java
+++ b/client/src/main/java/com/vaadin/client/ui/VDateFieldCalendar.java
@@ -15,6 +15,10 @@
  */
 package com.vaadin.client.ui;
 
+import static com.vaadin.shared.ui.datefield.DateResolution.DAY;
+import static com.vaadin.shared.ui.datefield.DateResolution.MONTH;
+import static com.vaadin.shared.ui.datefield.DateResolution.YEAR;
+
 import java.util.Date;
 import java.util.Map;
 
@@ -31,7 +35,7 @@ public class VDateFieldCalendar
         extends VAbstractDateFieldCalendar<VDateCalendarPanel, DateResolution> {
 
     public VDateFieldCalendar() {
-        super(GWT.create(VDateCalendarPanel.class), DateResolution.YEAR);
+        super(GWT.create(VDateCalendarPanel.class), YEAR);
     }
 
     /**
@@ -53,16 +57,14 @@ public class VDateFieldCalendar
         DateResolution resolution = getCurrentResolution();
         if (currentDate == null || date2.getTime() != currentDate.getTime()) {
             setCurrentDate((Date) date2.clone());
-            bufferedResolutions.put(DateResolution.YEAR.name(),
+            bufferedResolutions.put(YEAR,
                     // Java Date uses the year aligned to 1900 (no to zero).
                     // So we should add 1900 to get a correct year aligned to 0.
                     date2.getYear() + 1900);
-            if (resolution.compareTo(DateResolution.YEAR) < 0) {
-                bufferedResolutions.put(DateResolution.MONTH.name(),
-                        date2.getMonth() + 1);
-                if (resolution.compareTo(DateResolution.MONTH) < 0) {
-                    bufferedResolutions.put(DateResolution.DAY.name(),
-                            date2.getDate());
+            if (resolution.compareTo(YEAR) < 0) {
+                bufferedResolutions.put(MONTH, date2.getMonth() + 1);
+                if (resolution.compareTo(MONTH) < 0) {
+                    bufferedResolutions.put(DAY, date2.getDate());
                 }
             }
             sendBufferedValues();
@@ -71,8 +73,7 @@ public class VDateFieldCalendar
 
     @Override
     public void setCurrentResolution(DateResolution resolution) {
-        super.setCurrentResolution(
-                resolution == null ? DateResolution.YEAR : resolution);
+        super.setCurrentResolution(resolution == null ? YEAR : resolution);
     }
 
     @Override
@@ -82,7 +83,7 @@ public class VDateFieldCalendar
 
     @Override
     public boolean isYear(DateResolution resolution) {
-        return DateResolution.YEAR.equals(resolution);
+        return YEAR.equals(resolution);
     }
 
     @Override
diff --git a/client/src/main/java/com/vaadin/client/ui/VDateTimeFieldCalendar.java b/client/src/main/java/com/vaadin/client/ui/VDateTimeFieldCalendar.java
index 6e74bf45e7..a635b8b615 100644
--- a/client/src/main/java/com/vaadin/client/ui/VDateTimeFieldCalendar.java
+++ b/client/src/main/java/com/vaadin/client/ui/VDateTimeFieldCalendar.java
@@ -15,6 +15,13 @@
  */
 package com.vaadin.client.ui;
 
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.DAY;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.HOUR;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.MINUTE;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.MONTH;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.SECOND;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.YEAR;
+
 import java.util.Date;
 import java.util.Map;
 
@@ -32,8 +39,7 @@ public class VDateTimeFieldCalendar extends
         VAbstractDateFieldCalendar<VDateTimeCalendarPanel, DateTimeResolution> {
 
     public VDateTimeFieldCalendar() {
-        super(GWT.create(VDateTimeCalendarPanel.class),
-                DateTimeResolution.MINUTE);
+        super(GWT.create(VDateTimeCalendarPanel.class), MINUTE);
     }
 
     @Override
@@ -49,23 +55,17 @@ public class VDateTimeFieldCalendar extends
         DateTimeResolution resolution = getCurrentResolution();
         if (currentDate == null || date2.getTime() != currentDate.getTime()) {
             setCurrentDate((Date) date2.clone());
-            addBufferedResolution(DateTimeResolution.YEAR,
-                    date2.getYear() + 1900);
-            if (resolution.compareTo(DateTimeResolution.YEAR) < 0) {
-                addBufferedResolution(DateTimeResolution.MONTH,
-                        date2.getMonth() + 1);
-                if (resolution.compareTo(DateTimeResolution.MONTH) < 0) {
-                    addBufferedResolution(DateTimeResolution.DAY,
-                            date2.getDate());
-                    if (resolution.compareTo(DateTimeResolution.DAY) < 0) {
-                        addBufferedResolution(DateTimeResolution.HOUR,
-                                date2.getHours());
-                        if (resolution.compareTo(DateTimeResolution.HOUR) < 0) {
-                            addBufferedResolution(DateTimeResolution.MINUTE,
-                                    date2.getMinutes());
-                            if (resolution
-                                    .compareTo(DateTimeResolution.MINUTE) < 0) {
-                                addBufferedResolution(DateTimeResolution.SECOND,
+            bufferedResolutions.put(YEAR, date2.getYear() + 1900);
+            if (resolution.compareTo(YEAR) < 0) {
+                bufferedResolutions.put(MONTH, date2.getMonth() + 1);
+                if (resolution.compareTo(MONTH) < 0) {
+                    bufferedResolutions.put(DAY, date2.getDate());
+                    if (resolution.compareTo(DAY) < 0) {
+                        bufferedResolutions.put(HOUR, date2.getHours());
+                        if (resolution.compareTo(HOUR) < 0) {
+                            bufferedResolutions.put(MINUTE, date2.getMinutes());
+                            if (resolution.compareTo(MINUTE) < 0) {
+                                bufferedResolutions.put(SECOND,
                                         date2.getSeconds());
                             }
                         }
@@ -76,23 +76,17 @@ public class VDateTimeFieldCalendar extends
         }
     }
 
-    private void addBufferedResolution(DateTimeResolution resolution,
-            Integer value) {
-        bufferedResolutions.put(resolution.name(), value);
-    }
-
     @Override
     public String resolutionAsString() {
-        if (getCurrentResolution().compareTo(DateTimeResolution.DAY) >= 0) {
+        if (getCurrentResolution().compareTo(DAY) >= 0) {
             return getResolutionVariable(getCurrentResolution());
-        } else {
-            return "full";
         }
+        return "full";
     }
 
     @Override
     public boolean isYear(DateTimeResolution resolution) {
-        return DateTimeResolution.YEAR.equals(resolution);
+        return YEAR.equals(resolution);
     }
 
     @Override
diff --git a/client/src/main/java/com/vaadin/client/ui/VPopupCalendar.java b/client/src/main/java/com/vaadin/client/ui/VPopupCalendar.java
index 65c47f8c6c..970ccfb71a 100644
--- a/client/src/main/java/com/vaadin/client/ui/VPopupCalendar.java
+++ b/client/src/main/java/com/vaadin/client/ui/VPopupCalendar.java
@@ -15,6 +15,10 @@
  */
 package com.vaadin.client.ui;
 
+import static com.vaadin.shared.ui.datefield.DateResolution.DAY;
+import static com.vaadin.shared.ui.datefield.DateResolution.MONTH;
+import static com.vaadin.shared.ui.datefield.DateResolution.YEAR;
+
 import java.util.Date;
 import java.util.Map;
 
@@ -32,7 +36,7 @@ public class VPopupCalendar
         extends VAbstractPopupCalendar<VDateCalendarPanel, DateResolution> {
 
     public VPopupCalendar() {
-        super(GWT.create(VDateCalendarPanel.class), DateResolution.YEAR);
+        super(GWT.create(VDateCalendarPanel.class), YEAR);
     }
 
     @Override
@@ -47,24 +51,23 @@ public class VPopupCalendar
 
     @Override
     public void setCurrentResolution(DateResolution resolution) {
-        super.setCurrentResolution(
-                resolution == null ? DateResolution.YEAR : resolution);
+        super.setCurrentResolution(resolution == null ? YEAR : resolution);
     }
 
     public static Date makeDate(Map<DateResolution, Integer> dateValues) {
-        if (dateValues.get(DateResolution.YEAR) == null) {
+        if (dateValues.get(YEAR) == null) {
             return null;
         }
         Date date = new Date(2000 - 1900, 0, 1);
-        Integer year = dateValues.get(DateResolution.YEAR);
+        Integer year = dateValues.get(YEAR);
         if (year != null) {
             date.setYear(year - 1900);
         }
-        Integer month = dateValues.get(DateResolution.MONTH);
+        Integer month = dateValues.get(MONTH);
         if (month != null) {
             date.setMonth(month - 1);
         }
-        Integer day = dateValues.get(DateResolution.DAY);
+        Integer day = dateValues.get(DAY);
         if (day != null) {
             date.setDate(day);
         }
@@ -73,7 +76,7 @@ public class VPopupCalendar
 
     @Override
     public boolean isYear(DateResolution resolution) {
-        return DateResolution.YEAR.equals(resolution);
+        return YEAR.equals(resolution);
     }
 
     @Override
@@ -82,31 +85,27 @@ public class VPopupCalendar
     }
 
     @Override
-    protected void updateDateVariables() {
-        super.updateDateVariables();
-        DateResolution resolution = getCurrentResolution();
-        // Update variables
-        // (only the smallest defining resolution needs to be
-        // immediate)
+    protected void updateBufferedResolutions() {
+        super.updateBufferedResolutions();
         Date currentDate = getDate();
-        if (resolution.compareTo(DateResolution.MONTH) <= 0) {
-            bufferedResolutions.put(DateResolution.MONTH.name(),
-                    currentDate != null ? currentDate.getMonth() + 1 : null);
-        }
-        if (resolution.compareTo(DateResolution.DAY) <= 0) {
-            bufferedResolutions.put(DateResolution.DAY.name(),
-                    currentDate != null ? currentDate.getDate() : null);
+        if (currentDate != null) {
+            DateResolution resolution = getCurrentResolution();
+            if (resolution.compareTo(MONTH) <= 0) {
+                bufferedResolutions.put(MONTH, currentDate.getMonth() + 1);
+            }
+            if (resolution.compareTo(DAY) <= 0) {
+                bufferedResolutions.put(DAY, currentDate.getDate());
+            }
         }
-        sendBufferedValues();
     }
 
     @Override
     protected String cleanFormat(String format) {
         // Remove unnecessary d & M if resolution is too low
-        if (getCurrentResolution().compareTo(DateResolution.DAY) > 0) {
+        if (getCurrentResolution().compareTo(DAY) > 0) {
             format = format.replaceAll("d", "");
         }
-        if (getCurrentResolution().compareTo(DateResolution.MONTH) > 0) {
+        if (getCurrentResolution().compareTo(MONTH) > 0) {
             format = format.replaceAll("M", "");
         }
         return super.cleanFormat(format);
diff --git a/client/src/main/java/com/vaadin/client/ui/VPopupTimeCalendar.java b/client/src/main/java/com/vaadin/client/ui/VPopupTimeCalendar.java
index ff740efbca..39ae704651 100644
--- a/client/src/main/java/com/vaadin/client/ui/VPopupTimeCalendar.java
+++ b/client/src/main/java/com/vaadin/client/ui/VPopupTimeCalendar.java
@@ -15,6 +15,13 @@
  */
 package com.vaadin.client.ui;
 
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.DAY;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.HOUR;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.MINUTE;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.MONTH;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.SECOND;
+import static com.vaadin.shared.ui.datefield.DateTimeResolution.YEAR;
+
 import java.util.Date;
 import java.util.Map;
 
@@ -36,8 +43,7 @@ public class VPopupTimeCalendar extends
         VAbstractPopupCalendar<VDateTimeCalendarPanel, DateTimeResolution> {
 
     public VPopupTimeCalendar() {
-        super(GWT.create(VDateTimeCalendarPanel.class),
-                DateTimeResolution.MINUTE);
+        super(GWT.create(VDateTimeCalendarPanel.class), MINUTE);
     }
 
     @Override
@@ -47,45 +53,43 @@ public class VPopupTimeCalendar extends
 
     @Override
     public String resolutionAsString() {
-        if (getCurrentResolution().compareTo(DateTimeResolution.DAY) >= 0) {
+        if (getCurrentResolution().compareTo(DAY) >= 0) {
             return getResolutionVariable(getCurrentResolution());
-        } else {
-            return "full";
         }
+        return "full";
     }
 
     @Override
     public void setCurrentResolution(DateTimeResolution resolution) {
-        super.setCurrentResolution(
-                resolution == null ? DateTimeResolution.MINUTE : resolution);
+        super.setCurrentResolution(resolution == null ? MINUTE : resolution);
     }
 
     public static Date makeDate(Map<DateTimeResolution, Integer> dateValues) {
-        if (dateValues.get(DateTimeResolution.YEAR) == null) {
+        if (dateValues.get(YEAR) == null) {
             return null;
         }
         Date date = new Date(2000 - 1900, 0, 1);
-        Integer year = dateValues.get(DateTimeResolution.YEAR);
+        Integer year = dateValues.get(YEAR);
         if (year != null) {
             date.setYear(year - 1900);
         }
-        Integer month = dateValues.get(DateTimeResolution.MONTH);
+        Integer month = dateValues.get(MONTH);
         if (month != null) {
             date.setMonth(month - 1);
         }
-        Integer day = dateValues.get(DateTimeResolution.DAY);
+        Integer day = dateValues.get(DAY);
         if (day != null) {
             date.setDate(day);
         }
-        Integer hour = dateValues.get(DateTimeResolution.HOUR);
+        Integer hour = dateValues.get(HOUR);
         if (hour != null) {
             date.setHours(hour);
         }
-        Integer minute = dateValues.get(DateTimeResolution.MINUTE);
+        Integer minute = dateValues.get(MINUTE);
         if (minute != null) {
             date.setMinutes(minute);
         }
-        Integer second = dateValues.get(DateTimeResolution.SECOND);
+        Integer second = dateValues.get(SECOND);
         if (second != null) {
             date.setSeconds(second);
         }
@@ -94,7 +98,7 @@ public class VPopupTimeCalendar extends
 
     @Override
     public boolean isYear(DateTimeResolution resolution) {
-        return DateTimeResolution.YEAR.equals(resolution);
+        return YEAR.equals(resolution);
     }
 
     @Override
@@ -103,38 +107,27 @@ public class VPopupTimeCalendar extends
     }
 
     @Override
-    protected void updateDateVariables() {
-        super.updateDateVariables();
-        DateTimeResolution resolution = getCurrentResolution();
-        // (only the smallest defining resolution needs to be
-        // immediate)
+    protected void updateBufferedResolutions() {
+        super.updateBufferedResolutions();
         Date currentDate = getDate();
-        if (resolution.compareTo(DateTimeResolution.MONTH) <= 0) {
-            addBufferedResolution(DateTimeResolution.MONTH,
-                    currentDate != null ? currentDate.getMonth() + 1 : null);
-        }
-        if (resolution.compareTo(DateTimeResolution.DAY) <= 0) {
-            addBufferedResolution(DateTimeResolution.DAY,
-                    currentDate != null ? currentDate.getDate() : null);
-        }
-        if (resolution.compareTo(DateTimeResolution.HOUR) <= 0) {
-            addBufferedResolution(DateTimeResolution.HOUR,
-                    currentDate != null ? currentDate.getHours() : null);
-        }
-        if (resolution.compareTo(DateTimeResolution.MINUTE) <= 0) {
-            addBufferedResolution(DateTimeResolution.MINUTE,
-                    currentDate != null ? currentDate.getMinutes() : null);
-        }
-        if (resolution.compareTo(DateTimeResolution.SECOND) <= 0) {
-            addBufferedResolution(DateTimeResolution.SECOND,
-                    currentDate != null ? currentDate.getSeconds() : null);
+        if (currentDate != null) {
+            DateTimeResolution resolution = getCurrentResolution();
+            if (resolution.compareTo(MONTH) <= 0) {
+                bufferedResolutions.put(MONTH, currentDate.getMonth() + 1);
+            }
+            if (resolution.compareTo(DAY) <= 0) {
+                bufferedResolutions.put(DAY, currentDate.getDate());
+            }
+            if (resolution.compareTo(HOUR) <= 0) {
+                bufferedResolutions.put(HOUR, currentDate.getHours());
+            }
+            if (resolution.compareTo(MINUTE) <= 0) {
+                bufferedResolutions.put(MINUTE, currentDate.getMinutes());
+            }
+            if (resolution.compareTo(SECOND) <= 0) {
+                bufferedResolutions.put(SECOND, currentDate.getSeconds());
+            }
         }
-        sendBufferedValues();
-    }
-
-    private void addBufferedResolution(DateTimeResolution resolutionToAdd,
-            Integer value) {
-        bufferedResolutions.put(resolutionToAdd.name(), value);
     }
 
     @Override
@@ -144,16 +137,12 @@ public class VPopupTimeCalendar extends
         super.updateValue(newDate);
         DateTimeResolution resolution = getCurrentResolution();
         if (currentDate == null || newDate.getTime() != currentDate.getTime()) {
-            if (resolution.compareTo(DateTimeResolution.DAY) < 0) {
-                bufferedResolutions.put(DateTimeResolution.HOUR.name(),
-                        newDate.getHours());
-                if (resolution.compareTo(DateTimeResolution.HOUR) < 0) {
-                    bufferedResolutions.put(DateTimeResolution.MINUTE.name(),
-                            newDate.getMinutes());
-                    if (resolution.compareTo(DateTimeResolution.MINUTE) < 0) {
-                        bufferedResolutions.put(
-                                DateTimeResolution.SECOND.name(),
-                                newDate.getSeconds());
+            if (resolution.compareTo(DAY) < 0) {
+                bufferedResolutions.put(HOUR, newDate.getHours());
+                if (resolution.compareTo(HOUR) < 0) {
+                    bufferedResolutions.put(MINUTE, newDate.getMinutes());
+                    if (resolution.compareTo(MINUTE) < 0) {
+                        bufferedResolutions.put(SECOND, newDate.getSeconds());
                     }
                 }
             }
@@ -164,50 +153,45 @@ public class VPopupTimeCalendar extends
     protected String createFormatString() {
         if (isYear(getCurrentResolution())) {
             return "yyyy"; // force full year
-        } else {
-
-            try {
-                String frmString = LocaleService.getDateFormat(currentLocale);
-                frmString = cleanFormat(frmString);
-                // String delim = LocaleService
-                // .getClockDelimiter(currentLocale);
-                if (getCurrentResolution()
-                        .compareTo(DateTimeResolution.HOUR) <= 0) {
-                    if (dts.isTwelveHourClock()) {
-                        frmString += " hh";
-                    } else {
-                        frmString += " HH";
-                    }
-                    if (getCurrentResolution()
-                            .compareTo(DateTimeResolution.MINUTE) <= 0) {
-                        frmString += ":mm";
-                        if (getCurrentResolution()
-                                .compareTo(DateTimeResolution.SECOND) <= 0) {
-                            frmString += ":ss";
-                        }
-                    }
-                    if (dts.isTwelveHourClock()) {
-                        frmString += " aaa";
+        }
+        try {
+            String frmString = LocaleService.getDateFormat(currentLocale);
+            frmString = cleanFormat(frmString);
+            // String delim = LocaleService
+            // .getClockDelimiter(currentLocale);
+            if (getCurrentResolution().compareTo(HOUR) <= 0) {
+                if (dts.isTwelveHourClock()) {
+                    frmString += " hh";
+                } else {
+                    frmString += " HH";
+                }
+                if (getCurrentResolution().compareTo(MINUTE) <= 0) {
+                    frmString += ":mm";
+                    if (getCurrentResolution().compareTo(SECOND) <= 0) {
+                        frmString += ":ss";
                     }
                 }
-
-                return frmString;
-            } catch (LocaleNotLoadedException e) {
-                // TODO should die instead? Can the component survive
-                // without format string?
-                VConsole.error(e);
-                return null;
+                if (dts.isTwelveHourClock()) {
+                    frmString += " aaa";
+                }
             }
+
+            return frmString;
+        } catch (LocaleNotLoadedException e) {
+            // TODO should die instead? Can the component survive
+            // without format string?
+            VConsole.error(e);
+            return null;
         }
     }
 
     @Override
     protected String cleanFormat(String format) {
         // Remove unnecessary d & M if resolution is too low
-        if (getCurrentResolution().compareTo(DateTimeResolution.DAY) > 0) {
+        if (getCurrentResolution().compareTo(DAY) > 0) {
             format = format.replaceAll("d", "");
         }
-        if (getCurrentResolution().compareTo(DateTimeResolution.MONTH) > 0) {
+        if (getCurrentResolution().compareTo(MONTH) > 0) {
             format = format.replaceAll("M", "");
         }
         return super.cleanFormat(format);
diff --git a/client/src/main/java/com/vaadin/client/ui/datefield/AbstractDateFieldConnector.java b/client/src/main/java/com/vaadin/client/ui/datefield/AbstractDateFieldConnector.java
index 2aad416343..b7849938af 100644
--- a/client/src/main/java/com/vaadin/client/ui/datefield/AbstractDateFieldConnector.java
+++ b/client/src/main/java/com/vaadin/client/ui/datefield/AbstractDateFieldConnector.java
@@ -54,10 +54,9 @@ public abstract class AbstractDateFieldConnector<R extends Enum<R>>
         Stream<R> resolutions = widget.getResolutions();
         R resolution = widget.getCurrentResolution();
         return resolutions.collect(Collectors.toMap(Function.identity(),
-                res -> res == null ? null
-                        : (resolution.compareTo(res) <= 0)
-                                ? stateResolutions.get(res.name())
-                                : null));
+                res -> resolution.compareTo(res) <= 0
+                        ? stateResolutions.get(res.name())
+                        : null));
     }
 
     /**
@@ -68,14 +67,14 @@ public abstract class AbstractDateFieldConnector<R extends Enum<R>>
      * @since
      */
     protected Map<R, Integer> getDefaultValues() {
+        VDateField<R> widget = getWidget();
         Map<String, Integer> stateResolutions = getState().resolutions;
-        Stream<R> resolutions = getWidget().getResolutions();
-        R resolution = getWidget().getCurrentResolution();
+        Stream<R> resolutions = widget.getResolutions();
+        R resolution = widget.getCurrentResolution();
         return resolutions.collect(Collectors.toMap(Function.identity(),
-                res -> res == null ? null
-                        : (resolution.compareTo(res) <= 0)
-                                ? stateResolutions.get("default-" + res.name())
-                                : null));
+                res -> resolution.compareTo(res) <= 0
+                        ? stateResolutions.get("default-" + res.name())
+                        : null));
     }
 
     @SuppressWarnings("unchecked")
diff --git a/server/src/main/java/com/vaadin/ui/AbstractComponent.java b/server/src/main/java/com/vaadin/ui/AbstractComponent.java
index 88b42d5757..7a87230125 100644
--- a/server/src/main/java/com/vaadin/ui/AbstractComponent.java
+++ b/server/src/main/java/com/vaadin/ui/AbstractComponent.java
@@ -91,7 +91,7 @@ public abstract class AbstractComponent extends AbstractClientConnector
     /**
      * The internal error message of the component.
      */
-    private ErrorMessage componentError = null;
+    private ErrorMessage componentError;
 
     /**
      * Locale of this component.
diff --git a/server/src/main/java/com/vaadin/ui/AbstractDateField.java b/server/src/main/java/com/vaadin/ui/AbstractDateField.java
index 67067bd070..965c2f652a 100644
--- a/server/src/main/java/com/vaadin/ui/AbstractDateField.java
+++ b/server/src/main/java/com/vaadin/ui/AbstractDateField.java
@@ -77,10 +77,9 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     private AbstractDateFieldServerRpc rpc = new AbstractDateFieldServerRpc() {
 
         @Override
-        public void update(String newDateString, boolean invalidDateString,
+        public void update(String newDateString,
                 Map<String, Integer> resolutions) {
-            Set<String> resolutionNames = getResolutions()
-                    .map(AbstractDateField.this::getResolutionVariable)
+            Set<String> resolutionNames = getResolutions().map(Enum::name)
                     .collect(Collectors.toSet());
             resolutionNames.retainAll(resolutions.keySet());
             if (!isReadOnly()
@@ -109,7 +108,8 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
                     if (newDateString == null || newDateString.isEmpty()) {
                         setValue(newDate, true);
                     } else {
-                        if (invalidDateString) {
+                        // invalid date string
+                        if (resolutions.isEmpty()) {
                             Result<T> parsedDate = handleUnparsableDateString(
                                     dateString);
                             parsedDate.ifOk(v -> setValue(v, true));
@@ -173,7 +173,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     /* Constructors */
 
     /**
-     * Constructs an empty <code>AbstractDateField</code> with no caption and
+     * Constructs an empty {@code AbstractDateField} with no caption and
      * specified {@code resolution}.
      *
      * @param resolution
@@ -185,10 +185,10 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     }
 
     /**
-     * Constructs an empty <code>AbstractDateField</code> with caption.
+     * Constructs an empty {@code AbstractDateField} with caption.
      *
      * @param caption
-     *            the caption of the datefield.
+     *            the caption of the datefield
      * @param resolution
      *            initial resolution for the field, not {@code null}
      */
@@ -198,11 +198,11 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     }
 
     /**
-     * Constructs a new <code>AbstractDateField</code> with the given caption
-     * and initial text contents.
+     * Constructs a new {@code AbstractDateField} with the given caption and
+     * initial text contents.
      *
      * @param caption
-     *            the caption <code>String</code> for the editor.
+     *            the caption {@code String} for the editor.
      * @param value
      *            the date/time value.
      * @param resolution
@@ -227,24 +227,31 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
      * Construct a date object from the individual field values received from
      * the client.
      *
+     * @param resolutions
+     *            map of time unit (resolution) name and value, the key is the
+     *            resolution name e.g. "HOUR", "MINUTE", the value can be
+     *            {@code null}
+     * @param oldDate
+     *            used as a fallback to get needed values if they are not
+     *            defined in the specified {@code resolutions}
+     * 
+     * @return the date object built from the specified resolutions
      * @since
      */
-    protected T reconstructDateFromFields(Map<String, Integer> variables,
+    protected T reconstructDateFromFields(Map<String, Integer> resolutions,
             T oldDate) {
         Map<R, Integer> calendarFields = new HashMap<>();
 
         for (R resolution : getResolutionsHigherOrEqualTo(getResolution())) {
             // Only handle what the client is allowed to send. The same
             // resolutions that are painted
-            String variableName = getResolutionVariable(resolution);
+            String resolutionName = resolution.name();
 
-            Integer newValue = variables.get(variableName);
-            if (newValue != null) {
-                calendarFields.put(resolution, newValue);
-            } else {
-                calendarFields.put(resolution,
-                        getDatePart(oldDate, resolution));
+            Integer newValue = resolutions.get(resolutionName);
+            if (newValue == null) {
+                newValue = getDatePart(oldDate, resolution);
             }
+            calendarFields.put(resolution, newValue);
         }
         return buildDate(calendarFields);
     }
@@ -252,8 +259,8 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     /**
      * Sets the start range for this component. If the value is set before this
      * date (taking the resolution into account), the component will not
-     * validate. If <code>startDate</code> is set to <code>null</code>, any
-     * value before <code>endDate</code> will be accepted by the range
+     * validate. If {@code startDate} is set to {@code null}, any value before
+     * {@code endDate} will be accepted by the range
      *
      * @param startDate
      *            - the allowed range's start date
@@ -315,12 +322,12 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     /**
      * Sets the end range for this component. If the value is set after this
      * date (taking the resolution into account), the component will not
-     * validate. If <code>endDate</code> is set to <code>null</code>, any value
-     * after <code>startDate</code> will be accepted by the range.
+     * validate. If {@code endDate} is set to {@code null}, any value after
+     * {@code startDate} will be accepted by the range.
      *
      * @param endDate
-     *            - the allowed range's end date (inclusive, based on the
-     *            current resolution)
+     *            the allowed range's end date (inclusive, based on the current
+     *            resolution)
      */
     public void setRangeEnd(T endDate) {
         Date date = convertToDate(endDate);
@@ -336,7 +343,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     /**
      * Returns the precise rangeStart used.
      *
-     * @return the precise rangeStart used, may be null.
+     * @return the precise rangeStart used, may be {@code null}.
      */
     public T getRangeStart() {
         return convertFromDate(getState(false).rangeStart);
@@ -345,7 +352,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     /**
      * Returns the precise rangeEnd used.
      *
-     * @return the precise rangeEnd used, may be null.
+     * @return the precise rangeEnd used, may be {@code null}.
      */
     public T getRangeEnd() {
         return convertFromDate(getState(false).rangeEnd);
@@ -423,14 +430,14 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
 
         // Only paint variables for the resolution and up, e.g. Resolution DAY
         // paints DAY,MONTH,YEAR
-        for (R res : getResolutionsHigherOrEqualTo(getResolution())) {
-            String variableName = getResolutionVariable(res);
+        for (R resolution : getResolutionsHigherOrEqualTo(getResolution())) {
+            String resolutionName = resolution.name();
 
-            Integer value = getValuePart(currentDate, res);
-            resolutions.put(variableName, value);
+            Integer value = getValuePart(currentDate, resolution);
+            resolutions.put(resolutionName, value);
 
-            Integer defaultValuePart = getValuePart(defaultValue, res);
-            resolutions.put("default-" + variableName, defaultValuePart);
+            Integer defaultValuePart = getValuePart(defaultValue, resolution);
+            resolutions.put("default-" + resolutionName, defaultValuePart);
         }
     }
 
@@ -501,6 +508,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
      * default value is set, current date/time is used.
      *
      * @param defaultValue
+     *            the default value, may be {@code null}
      * @since 8.1.2
      */
     public void setDefaultValue(T defaultValue) {
@@ -581,9 +589,11 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
      * {@link #handleUnparsableDateString(String)} method is overridden, the
      * localized message from its exception is used.
      *
+     * @param parsingErrorMessage
+     *            the default parsing error message
+     *
      * @see #getParseErrorMessage()
      * @see #handleUnparsableDateString(String)
-     * @param parsingErrorMessage
      */
     public void setParseErrorMessage(String parsingErrorMessage) {
         defaultParseErrorMessage = parsingErrorMessage;
@@ -628,8 +638,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
     }
 
     /**
-     * Formats date according to the components locale. To be reimplemented in
-     * subclasses.
+     * Formats date according to the components locale.
      *
      * @param value
      *            the date or {@code null}
@@ -637,9 +646,7 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
      *         {@code null}
      * @since 8.1.1
      */
-    protected String formatDate(T value) {
-        return Objects.toString(value, "");
-    }
+    protected abstract String formatDate(T value);
 
     @Override
     public void writeDesign(Element design, DesignContext designContext) {
@@ -684,11 +691,10 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
 
         this.value = value;
         // Also set the internal dateString
-        if (value != null) {
-            dateString = formatDate(value);
-        } else {
-            dateString = formatDate(getEmptyValue());
+        if (value == null) {
+            value = getEmptyValue();
         }
+        dateString = formatDate(value);
         RangeValidator<T> validator = getRangeValidator();// TODO move range
                                                           // check to internal
                                                           // validator?
@@ -717,9 +723,10 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
      * given {@code resolution}.
      *
      * @param date
-     *            the given date
+     *            the given date, can be {@code null}
      * @param resolution
-     *            the resolution to extract a value from the date by
+     *            the resolution to extract a value from the date by, not
+     *            {@code null}
      * @return the integer value part of the date by the given resolution
      */
     protected abstract int getDatePart(T date, R resolution);
@@ -764,10 +771,6 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
      */
     protected abstract Date convertToDate(T date);
 
-    private String getResolutionVariable(R resolution) {
-        return resolution.name();
-    }
-
     @SuppressWarnings("unchecked")
     private Stream<R> getResolutions() {
         Type resolutionType = GenericTypeReflector.getTypeParameter(getClass(),
@@ -776,11 +779,10 @@ public abstract class AbstractDateField<T extends Temporal & TemporalAdjuster &
             Class<?> clazz = (Class<?>) resolutionType;
             return Stream.of(clazz.getEnumConstants())
                     .map(object -> (R) object);
-        } else {
-            throw new RuntimeException("Cannot detect resoluton type "
-                    + Optional.ofNullable(resolutionType).map(Type::getTypeName)
-                            .orElse(null));
         }
+        throw new RuntimeException("Cannot detect resoluton type "
+                + Optional.ofNullable(resolutionType).map(Type::getTypeName)
+                        .orElse(null));
     }
 
     private Iterable<R> getResolutionsHigherOrEqualTo(R resoution) {
diff --git a/server/src/test/java/com/vaadin/tests/server/component/datefield/DateFieldListenersTest.java b/server/src/test/java/com/vaadin/tests/server/component/datefield/DateFieldListenersTest.java
index 4edc2a30df..eea1e33137 100644
--- a/server/src/test/java/com/vaadin/tests/server/component/datefield/DateFieldListenersTest.java
+++ b/server/src/test/java/com/vaadin/tests/server/component/datefield/DateFieldListenersTest.java
@@ -50,6 +50,11 @@ public class DateFieldListenersTest extends AbstractListenerMethodsTestBase {
         protected Date convertToDate(LocalDateTime date) {
             return null;
         }
+
+        @Override
+        protected String formatDate(LocalDateTime value) {
+            return null;
+        }
     }
 
     @Test
diff --git a/shared/src/main/java/com/vaadin/shared/ui/datefield/AbstractDateFieldServerRpc.java b/shared/src/main/java/com/vaadin/shared/ui/datefield/AbstractDateFieldServerRpc.java
index 2ef8993fb6..cdd8e30815 100644
--- a/shared/src/main/java/com/vaadin/shared/ui/datefield/AbstractDateFieldServerRpc.java
+++ b/shared/src/main/java/com/vaadin/shared/ui/datefield/AbstractDateFieldServerRpc.java
@@ -33,15 +33,13 @@ public interface AbstractDateFieldServerRpc extends ServerRpc {
      *            the value of the text field part. It enables analyzing invalid
      *            input on the server. {@code null} if the date was chosen with
      *            popup calendar or contains user-typed string
-     * @param invalidDateString
-     *            Whether the last date string is invalid or not
      * @param resolutions
-     *            map of time unit (resolution) name and value, name is the
-     *            lower-case resolution name e.g. "hour", "minute", and value
-     *            can be {@code null}
+     *            map of time unit (resolution) name and value, the key is the
+     *            resolution name e.g. "HOUR", "MINUTE", the value can be
+     *            {@code null}. If the map is empty, that means the
+     *            {@code newDateString} is invalid
      */
-    void update(String newDateString, boolean invalidDateString,
-            Map<String, Integer> resolutions);
+    void update(String newDateString, Map<String, Integer> resolutions);
 
     /**
      * Indicates to the server that the client-side has lost focus.