Fix bug that prevents other surrounders to act

Subtle issue: I returned null on my surround-with range adjuster which
would prevent the whole surround framework to test and apply other surrounders.

This fixes #85

src/de/halirutan/mathematica/codeinsight/editoractions/enter/MathematicaEnterInsideFunctionHandler.java

@@ -136,6 +136,7 @@ public Result preprocessEnter(@NotNull final PsiFile file,
     if (project != null) {
       CodeStyleManager.getInstance(project).adjustLineIndent(editor.getDocument(), caretOffset.get() + 1);
     }
+    PsiDocumentManager.getInstance(file.getProject()).commitDocument(document);
     return Result.DefaultForceIndent;
   }
 

src/de/halirutan/mathematica/codeinsight/surround/AbstractSurrounder.java

@@ -29,6 +29,7 @@
 import com.intellij.openapi.util.TextRange;
 import com.intellij.psi.PsiElement;
 import com.intellij.util.IncorrectOperationException;
+import de.halirutan.mathematica.lang.psi.api.MathematicaPsiFile;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -42,7 +43,7 @@ abstract class AbstractSurrounder implements Surrounder {
 
   @Override
   public boolean isApplicable(@NotNull PsiElement[] elements) {
-    return true;
+    return elements.length > 0 && elements[0].getContainingFile() instanceof MathematicaPsiFile;
   }
 
   protected abstract String getOpening();

src/de/halirutan/mathematica/codeinsight/surround/MathematicaSurroundDescriptor.java

@@ -26,6 +26,7 @@
 import com.intellij.psi.PsiElement;
 import com.intellij.psi.PsiFile;
 import com.intellij.psi.util.PsiTreeUtil;
+import de.halirutan.mathematica.lang.psi.api.MathematicaPsiFile;
 import org.jetbrains.annotations.NotNull;
 
 /**
@@ -54,7 +55,10 @@ public boolean isExclusive() {
   @NotNull
   @Override
   public PsiElement[] getElementsToSurround(PsiFile file, int startOffset, int endOffset) {
-    return findElementsInRange(file, startOffset, endOffset);
+    if (file instanceof MathematicaPsiFile) {
+      return findElementsInRange(file, startOffset, endOffset);
+    }
+    return PsiElement.EMPTY_ARRAY;
   }
 
   private PsiElement[] findElementsInRange(PsiFile file, int startOffset, int endOffset) {

src/de/halirutan/mathematica/codeinsight/surround/MathematicaSurroundWithRangeAdjuster.java

@@ -33,6 +33,7 @@
 import com.intellij.psi.util.PsiUtilBase;
 import de.halirutan.mathematica.lang.MathematicaLanguage;
 import de.halirutan.mathematica.lang.psi.api.Expression;
+import de.halirutan.mathematica.lang.psi.api.MathematicaPsiFile;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -48,12 +49,18 @@ public class MathematicaSurroundWithRangeAdjuster implements SurroundWithRangeAd
   @Nullable
   @Override
   public TextRange adjustSurroundWithRange(PsiFile file, TextRange selectedRange) {
-    return adjustSurroundWithRange(file, selectedRange, true);
+    if (file instanceof MathematicaPsiFile) {
+      return adjustSurroundWithRange(file, selectedRange, true);
+    }
+    return selectedRange;
   }
 
   @Nullable
   @Override
   public TextRange adjustSurroundWithRange(PsiFile file, TextRange selectedRange, boolean hasSelection) {
+    if (!(file instanceof MathematicaPsiFile)) {
+      return selectedRange;
+    }
     int startOffset = selectedRange.getStartOffset();
     int endOffset = selectedRange.getEndOffset();
     if (endOffset < startOffset) {
@@ -103,6 +110,6 @@ public TextRange adjustSurroundWithRange(PsiFile file, TextRange selectedRange,
         return bestExpression.getTextRange();
       }
     }
-    return null;
+    return selectedRange;
   }
 }