Automatically choose first rule in grammar as start rule (#545)

* Fixes #460 so we automatically choose first rule in grammar as start rule but can still set to other rules.

Signed-off-by: Terence Parr <parrt@antlr.org>

* Upon save of grammar, update start rule and start rule display.

Signed-off-by: Terence Parr <parrt@antlr.org>

Author: parrt

src/main/java/org/antlr/intellij/plugin/ANTLRv4PluginController.java

@@ -16,7 +16,10 @@
 import com.intellij.openapi.editor.event.EditorMouseAdapter;
 import com.intellij.openapi.editor.event.EditorMouseEvent;
 import com.intellij.openapi.extensions.PluginId;
-import com.intellij.openapi.fileEditor.*;
+import com.intellij.openapi.fileEditor.FileDocumentManager;
+import com.intellij.openapi.fileEditor.FileEditorManager;
+import com.intellij.openapi.fileEditor.FileEditorManagerEvent;
+import com.intellij.openapi.fileEditor.FileEditorManagerListener;
 import com.intellij.openapi.progress.ProgressIndicator;
 import com.intellij.openapi.progress.ProgressManager;
 import com.intellij.openapi.progress.Task;
@@ -242,7 +245,7 @@ public void editorReleased(@NotNull EditorFactoryEvent event) {
 	}
 
 	/** The test ANTLR rule action triggers this event. This can occur
-	 *  only occur when the current editor the showing a grammar, because
+	 *  only occur when the current editor is showing a grammar, because
 	 *  that is the only time that the action is enabled. We will see
 	 *  a file changed event when the project loads the first grammar file.
 	 */
@@ -395,6 +398,12 @@ private String updateGrammarObjectsFromFile_(VirtualFile grammarFile) {
 				previewState.g = grammars[1];
 			}
 		}
+		else {
+			synchronized (previewState) { // build atomically
+				previewState.lg = null;
+				previewState.g = null;
+			}
+		}
 		return grammarFileName;
 	}
 
@@ -579,19 +588,25 @@ private class MyVirtualFileAdapter extends VirtualFileAdapter {
 		public void contentsChanged(VirtualFileEvent event) {
 			final VirtualFile vfile = event.getFile();
 			if ( !vfile.getName().endsWith(".g4") ) return;
-			if ( !projectIsClosed && !ApplicationManager.getApplication().isUnitTestMode()) grammarFileSavedEvent(vfile);
+			if ( !projectIsClosed && !ApplicationManager.getApplication().isUnitTestMode()) {
+				grammarFileSavedEvent(vfile);
+			}
 		}
 	}
 
 	private class MyFileEditorManagerAdapter implements FileEditorManagerListener {
 		@Override
 		public void selectionChanged(FileEditorManagerEvent event) {
-			if ( !projectIsClosed ) currentEditorFileChangedEvent(event.getOldFile(), event.getNewFile());
+			if ( !projectIsClosed ) {
+				currentEditorFileChangedEvent(event.getOldFile(), event.getNewFile());
+			}
 		}
 
 		@Override
 		public void fileClosed(FileEditorManager source, VirtualFile file) {
-			if ( !projectIsClosed ) editorFileClosedEvent(file);
+			if ( !projectIsClosed ) {
+				editorFileClosedEvent(file);
+			}
 		}
 	}
 

src/main/java/org/antlr/intellij/plugin/preview/InputPanel.java

@@ -9,7 +9,6 @@
 import com.intellij.openapi.editor.event.CaretListener;
 import com.intellij.openapi.editor.event.DocumentAdapter;
 import com.intellij.openapi.editor.event.DocumentEvent;
-import com.intellij.openapi.editor.event.EditorMouseEvent;
 import com.intellij.openapi.editor.ex.EditorEx;
 import com.intellij.openapi.editor.ex.EditorMarkupModel;
 import com.intellij.openapi.editor.markup.*;
@@ -235,6 +234,12 @@ public void documentChanged(DocumentEvent event) {
 
 	public void grammarFileSaved() {
 		clearParseErrors();
+		if ( previewState.startRuleName!=null ) {
+			setStartRuleName(previewState.grammarFile, previewState.startRuleName);
+		}
+		else {
+			resetStartRuleLabel();
+		}
 	}
 
 	public void switchToGrammar(PreviewState previewState, VirtualFile grammarFile) {

src/main/java/org/antlr/intellij/plugin/preview/PreviewEditorMouseListener.java

@@ -55,8 +55,7 @@ else if ( mouseEvent.isAltDown() ) {
 		InputPanel.clearDecisionEventHighlighters(editor);
 	}
 
-	public void rightClick(final PreviewState previewState, Editor editor, int offset)
-	{
+	public void rightClick(final PreviewState previewState, Editor editor, int offset) {
 		if (previewState.parsingResult == null) return;
 		final List<RangeHighlighter> highlightersAtOffset = MyActionUtils.getRangeHighlightersAtOffset(editor, offset);
 		if (highlightersAtOffset.size() == 0) {
@@ -80,7 +79,7 @@ else if ( lookaheadInfo != null ) {
 	}
 
 	@Override
-	public void mouseMoved(EditorMouseEvent e){
+	public void mouseMoved(EditorMouseEvent e) {
 		int offset = getEditorCharOffsetAndRemoveTokenHighlighters(e);
 		if ( offset<0 ) return;
 

src/main/java/org/antlr/intellij/plugin/preview/PreviewPanel.java

@@ -21,6 +21,7 @@
 import org.antlr.intellij.plugin.parsing.ParsingUtils;
 import org.antlr.intellij.plugin.parsing.PreviewParser;
 import org.antlr.intellij.plugin.profiler.ProfilerPanel;
+import org.antlr.v4.misc.OrderedHashMap;
 import org.antlr.v4.runtime.CommonToken;
 import org.antlr.v4.runtime.ParserRuleContext;
 import org.antlr.v4.runtime.Token;
@@ -273,6 +274,8 @@ public void grammarFileSaved(VirtualFile grammarFile) {
 		ANTLRv4PluginController controller = ANTLRv4PluginController.getInstance(project);
 		PreviewState previewState = controller.getPreviewState(grammarFile);
 
+		autoSetStartRule(previewState);
+
 		ensureStartRuleExists(grammarFile);
 		inputPanel.grammarFileSaved();
 
@@ -315,6 +318,8 @@ private void switchToGrammar(VirtualFile grammarFile) {
 		ANTLRv4PluginController controller = ANTLRv4PluginController.getInstance(project);
 		PreviewState previewState = controller.getPreviewState(grammarFile);
 
+		autoSetStartRule(previewState);
+
 		inputPanel.switchToGrammar(previewState, grammarFile);
 		profilerPanel.switchToGrammar(previewState, grammarFile);
 
@@ -328,6 +333,20 @@ private void switchToGrammar(VirtualFile grammarFile) {
 		setEnabled(previewState.g!=null || previewState.lg==null);
 	}
 
+	/** From 1.18, automatically set the start rule name to the first rule in the grammar
+	 * if none has been specified
+	 */
+	protected void autoSetStartRule(PreviewState previewState) {
+		if ( previewState.g==null || previewState.g.rules.size()==0 ) {
+			// If there is no grammar all of a sudden, we need to unset the previous rule name
+			previewState.startRuleName = null;
+		}
+		else if ( previewState.startRuleName==null ) {
+			OrderedHashMap<String, Rule> rules = previewState.g.rules;
+			previewState.startRuleName = rules.getElement(0).name;
+		}
+	}
+
 	@Override
 	public void setEnabled(boolean enabled) {
 		super.setEnabled(enabled);