Incorporating code review comments.

src/vs/workbench/parts/debug/electron-browser/debugHover.ts

@@ -104,30 +104,14 @@ export class DebugHoverWidget implements editorbrowser.IContentWidget {
 		return this.domNode;
 	}
 
-	public showAt(range: Range, hoveringOver: string, focus: boolean): TPromise<void> {
-		const pos = range.getStartPosition();
-		const model = this.editor.getModel();
-		const focusedStackFrame = this.debugService.getViewModel().getFocusedStackFrame();
-		if (!hoveringOver || !focusedStackFrame || (focusedStackFrame.source.uri.toString() !== model.uri.toString())) {
-			return;
-		}
+	private getHoveredExpression(lineContent: string, range: Range) : Range {
+		let matchingExpression = undefined;
+		let startOffset = 0;
 
-		const session = this.debugService.getActiveSession();
-		const canEvaluateForHovers: boolean = session.configuration.capabilities.supportsEvaluateForHovers;
-
-		const lineContent = model.getLineContent(pos.lineNumber);
-		let evaluatedExpression : TPromise<Expression> = undefined;
-		let matchingExpression: string = undefined;
-		let startOffset: number = 0;
-		if (canEvaluateForHovers) {
-			// If the debug adapter supports evaluation-based-hover, we need to try and guess what the expression under the mouse cursor is.
-			// Someday it might be nice if the language service could somehow provide this.
-			// But this code attempts to approximate the answer for a variety of languages.
 		// Some example supported expressions: myVar.prop, a.b.c.d, myVar?.prop, myVar->prop, MyClass::StaticProp, *myVar
-
 		// Match any character except a set of characters which often break interesting sub-expressions
 		let expression: RegExp = /([^()\[\]{}<>\s+\-/%~#^;=|,`!]|\->)+/g;
-			let result: RegExpExecArray = undefined;
+		let result = undefined;
 
 		// First find the full expression under the cursor
 		while (result = expression.exec(lineContent)) {
@@ -145,7 +129,7 @@ export class DebugHoverWidget implements editorbrowser.IContentWidget {
 		// For example in expression 'a.b.c.d', if the focus was under 'b', 'a.b' would be evaluated.
 		if (matchingExpression) {
 			let subExpression: RegExp = /\w+/g;
-				let subExpressionResult: RegExpExecArray = undefined;
+			let subExpressionResult = undefined;
 			while (subExpressionResult = subExpression.exec(matchingExpression)) {
 				let subEnd = subExpressionResult.index + 1 + startOffset + subExpressionResult[0].length;
 				if (subEnd >= range.endColumn) {
@@ -158,6 +142,31 @@ export class DebugHoverWidget implements editorbrowser.IContentWidget {
 			}
 		}
 
+		return matchingExpression ?
+			new Range(range.startLineNumber, startOffset, range.endLineNumber, startOffset + matchingExpression.length - 1) :
+			new Range(range.startLineNumber, 0, range.endLineNumber, 0);
+	}
+
+	public showAt(range: Range, hoveringOver: string, focus: boolean): TPromise<void> {
+		const pos = range.getStartPosition();
+		const model = this.editor.getModel();
+		const focusedStackFrame = this.debugService.getViewModel().getFocusedStackFrame();
+		if (!hoveringOver || !focusedStackFrame || (focusedStackFrame.source.uri.toString() !== model.uri.toString())) {
+			return;
+		}
+
+		const session = this.debugService.getActiveSession();
+		const canEvaluateForHovers: boolean = session.configuration.capabilities.supportsEvaluateForHovers;
+
+		const lineContent = model.getLineContent(pos.lineNumber);
+		let evaluatedExpression = undefined;
+		let matchingExpression = undefined;
+		let startOffset = 0;
+
+		if (canEvaluateForHovers) {
+			let expressionRange = this.getHoveredExpression(lineContent, range);
+			startOffset = expressionRange.startColumn;
+			let matchingExpression = lineContent.substring(expressionRange.startColumn - 1, expressionRange.endColumn);
 			evaluatedExpression = this.getExpressionSupportingEvaluate(session, matchingExpression);
 		}
 		else {