fix null handling for string funcs

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/branches/exprs@1145 f203690c-595d-4dc9-a70b-905162fa7fd2

src/main/java/com/healthmarketscience/jackcess/impl/expr/DefaultFunctions.java

@@ -222,6 +222,40 @@ public class DefaultFunctions
     protected abstract Value evalVar(EvalContext ctx, Value[] params);
   }
 
+  public static class StringFuncWrapper implements Function
+  {
+    private final String _name;
+    private final Function _delegate;
+
+    public StringFuncWrapper(Function delegate) {
+      _delegate = delegate;
+      _name = _delegate.getName() + NON_VAR_SUFFIX;
+    }
+
+    public String getName() {
+      return _name;
+    }
+
+    public boolean isPure() {
+      return _delegate.isPure();
+    }
+
+    public Value eval(EvalContext ctx, Value... params) {
+      Value result = _delegate.eval(ctx, params);
+      if(result.isNull()) {
+        // non-variant version does not do null-propagation, so force
+        // exception to be thrown here
+        result.getAsString();
+      }
+      return result;
+    }
+
+    @Override
+    public String toString() {
+      return getName() + "()";
+    }
+  }
+
   
   public static final Function IIF = registerFunc(new Func3("IIf") {
     @Override
@@ -497,10 +531,8 @@ public class DefaultFunctions
   }
 
   static Function registerStringFunc(Function func) {
-    // for our purposes the non-variant versions are the same function
-    // (e.g. "Foo" and "Foo$")
     registerFunc(func.getName(), func);
-    registerFunc(func.getName() + NON_VAR_SUFFIX, func);
+    registerFunc(new StringFuncWrapper(func));
     return func;
   }
 

src/main/java/com/healthmarketscience/jackcess/impl/expr/DefaultTextFunctions.java

@@ -66,7 +66,7 @@ public class DefaultTextFunctions
     }
   });
 
-  public static final Function CHR = registerStringFunc(new Func1("Chr") {
+  public static final Function CHR = registerStringFunc(new Func1NullIsNull("Chr") {
     @Override
     protected Value eval1(EvalContext ctx, Value param1) {
       int lv = param1.getAsLongInt();
@@ -79,7 +79,7 @@ public class DefaultTextFunctions
     }
   });
 
-  public static final Function CHRW = registerStringFunc(new Func1("ChrW") {
+  public static final Function CHRW = registerStringFunc(new Func1NullIsNull("ChrW") {
     @Override
     protected Value eval1(EvalContext ctx, Value param1) {
       int lv = param1.getAsLongInt();
@@ -88,7 +88,7 @@ public class DefaultTextFunctions
     }
   });
 
-  public static final Function STR = registerStringFunc(new Func1("Str") {
+  public static final Function STR = registerStringFunc(new Func1NullIsNull("Str") {
     @Override
     protected Value eval1(EvalContext ctx, Value param1) {
       BigDecimal bd = param1.getAsBigDecimal();

src/test/java/com/healthmarketscience/jackcess/impl/expr/DefaultFunctionsTest.java

@@ -59,6 +59,15 @@ public class DefaultFunctionsTest extends TestCase
     assertEquals("23072", eval("=Oct(9786)"));
     assertEquals(" 9786", eval("=Str(9786)"));
     assertEquals("-42", eval("=Str(-42)"));
+    assertEquals("-42", eval("=Str$(-42)"));
+    assertNull(eval("=Str(Null)"));
+
+    try {
+      eval("=Str$(Null)");
+      fail("UnsupportedOperationException should have been thrown");
+    } catch(UnsupportedOperationException expected) {
+      // success
+    }
 
     assertEquals(-1, eval("=CBool(\"1\")"));
     assertEquals(13, eval("=CByte(\"13\")"));