Null-annotated Ref class and fixed related compiler errors

This change fixes all compiler errors in JGit and replaces possible
NPE's with either appropriate exceptions, avoiding multiple "Nullable
return" method calls or early returning from the method.

Change-Id: I24c8a600ec962d61d5f40abf73eac4203e115240
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>

6 files changed, 58 insertions, 19 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
index cf13582db5..754cf361a9 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackFetchConnection.java
@@ -464,8 +464,12 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 		final PacketLineOut p = statelessRPC ? pckState : pckOut;
 		boolean first = true;
 		for (final Ref r : want) {
+			ObjectId objectId = r.getObjectId();
+			if (objectId == null) {
+				continue;
+			}
 			try {
-				if (walk.parseAny(r.getObjectId()).has(REACHABLE)) {
+				if (walk.parseAny(objectId).has(REACHABLE)) {
 					// We already have this object. Asking for it is
 					// not a very good idea.
 					//
@@ -478,7 +482,7 @@ public abstract class BasePackFetchConnection extends BasePackConnection
 
 			final StringBuilder line = new StringBuilder(46);
 			line.append("want "); //$NON-NLS-1$
-			line.append(r.getObjectId().name());
+			line.append(objectId.name());
 			if (first) {
 				line.append(enableCapabilities());
 				first = false;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackPushConnection.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackPushConnection.java
index 0834c359aa..4499f66d53 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackPushConnection.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BasePackPushConnection.java
@@ -239,8 +239,11 @@ public abstract class BasePackPushConnection extends BasePackConnection implemen
 			final StringBuilder sb = new StringBuilder();
 			ObjectId oldId = rru.getExpectedOldObjectId();
 			if (oldId == null) {
-				Ref adv = getRef(rru.getRemoteName());
-				oldId = adv != null ? adv.getObjectId() : ObjectId.zeroId();
+				final Ref advertised = getRef(rru.getRemoteName());
+				oldId = advertised != null ? advertised.getObjectId() : null;
+				if (oldId == null) {
+					oldId = ObjectId.zeroId();
+				}
 			}
 			sb.append(oldId.name());
 			sb.append(' ');
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
index 776a9f695a..c224d8eeb8 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/BaseReceivePack.java
@@ -1372,16 +1372,21 @@ public abstract class BaseReceivePack {
 				}
 			}
 
-			if (cmd.getType() == ReceiveCommand.Type.DELETE && ref != null
-					&& !ObjectId.zeroId().equals(cmd.getOldId())
-					&& !ref.getObjectId().equals(cmd.getOldId())) {
-				// Delete commands can be sent with the old id matching our
-				// advertised value, *OR* with the old id being 0{40}. Any
-				// other requested old id is invalid.
-				//
-				cmd.setResult(Result.REJECTED_OTHER_REASON,
-						JGitText.get().invalidOldIdSent);
-				continue;
+			if (cmd.getType() == ReceiveCommand.Type.DELETE && ref != null) {
+				ObjectId id = ref.getObjectId();
+				if (id == null) {
+					id = ObjectId.zeroId();
+				}
+				if (!ObjectId.zeroId().equals(cmd.getOldId())
+						&& !id.equals(cmd.getOldId())) {
+					// Delete commands can be sent with the old id matching our
+					// advertised value, *OR* with the old id being 0{40}. Any
+					// other requested old id is invalid.
+					//
+					cmd.setResult(Result.REJECTED_OTHER_REASON,
+							JGitText.get().invalidOldIdSent);
+					continue;
+				}
 			}
 
 			if (cmd.getType() == ReceiveCommand.Type.UPDATE) {
@@ -1391,8 +1396,15 @@ public abstract class BaseReceivePack {
 					cmd.setResult(Result.REJECTED_OTHER_REASON, JGitText.get().noSuchRef);
 					continue;
 				}
+				ObjectId id = ref.getObjectId();
+				if (id == null) {
+					// We cannot update unborn branch
+					cmd.setResult(Result.REJECTED_OTHER_REASON,
+							JGitText.get().cannotUpdateUnbornBranch);
+					continue;
+				}
 
-				if (!ref.getObjectId().equals(cmd.getOldId())) {
+				if (!id.equals(cmd.getOldId())) {
 					// A properly functioning client will send the same
 					// object id we advertised.
 					//
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/FetchProcess.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/FetchProcess.java
index 9aae1c37aa..c4b3f83048 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/FetchProcess.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/FetchProcess.java
@@ -397,11 +397,17 @@ class FetchProcess {
 	private void expandFetchTags() throws TransportException {
 		final Map<String, Ref> haveRefs = localRefs();
 		for (final Ref r : conn.getRefs()) {
-			if (!isTag(r))
+			if (!isTag(r)) {
+				continue;
+			}
+			ObjectId id = r.getObjectId();
+			if (id == null) {
 				continue;
+			}
 			final Ref local = haveRefs.get(r.getName());
-			if (local == null || !r.getObjectId().equals(local.getObjectId()))
+			if (local == null || !id.equals(local.getObjectId())) {
 				wantTag(r);
+			}
 		}
 	}
 
@@ -413,6 +419,11 @@ class FetchProcess {
 	private void want(final Ref src, final RefSpec spec)
 			throws TransportException {
 		final ObjectId newId = src.getObjectId();
+		if (newId == null) {
+			throw new NullPointerException(MessageFormat.format(
+					JGitText.get().transportProvidedRefWithNoObjectId,
+					src.getName()));
+		}
 		if (spec.getDestination() != null) {
 			final TrackingRefUpdate tru = createUpdate(spec, newId);
 			if (newId.equals(tru.getOldObjectId()))
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/PushProcess.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/PushProcess.java
index 4fd192dbb2..5cea88215a 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/PushProcess.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/PushProcess.java
@@ -188,8 +188,13 @@ class PushProcess {
 		final Map<String, RemoteRefUpdate> result = new HashMap<String, RemoteRefUpdate>();
 		for (final RemoteRefUpdate rru : toPush.values()) {
 			final Ref advertisedRef = connection.getRef(rru.getRemoteName());
-			final ObjectId advertisedOld = (advertisedRef == null ? ObjectId
-					.zeroId() : advertisedRef.getObjectId());
+			ObjectId advertisedOld = null;
+			if (advertisedRef != null) {
+				advertisedOld = advertisedRef.getObjectId();
+			}
+			if (advertisedOld == null) {
+				advertisedOld = ObjectId.zeroId();
+			}
 
 			if (rru.getNewObjectId().equals(advertisedOld)) {
 				if (rru.isDelete()) {
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkFetchConnection.java b/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkFetchConnection.java
index 1c6b8b7363..dfc3ee4c30 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkFetchConnection.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/transport/WalkFetchConnection.java
@@ -267,6 +267,10 @@ class WalkFetchConnection extends BaseFetchConnection {
 		final HashSet<ObjectId> inWorkQueue = new HashSet<ObjectId>();
 		for (final Ref r : want) {
 			final ObjectId id = r.getObjectId();
+			if (id == null) {
+				throw new NullPointerException(MessageFormat.format(
+						JGitText.get().transportProvidedRefWithNoObjectId, r.getName()));
+			}
 			try {
 				final RevObject obj = revWalk.parseAny(id);
 				if (obj.has(COMPLETE))