Cursor moves to beginning of file while stepping if an exception occurs during a test

[osaxma]

Hello there,

It's been a while since I came by .. hope all is well!

Describe the bug

When running a test in debug mode, the cursor in the test file moves to the beginning of the file after each run.

This is inconvenient since after each time I run the test, I have to scroll back to the line wherever the test is to run it again.

To Reproduce
Steps to reproduce the behavior:

1. create a new dart project (i.e. dart create debug_cursor_issue)

2. go to the test file and paste the sample code there (given below).

3. scroll down to the test

4. place the cursor somewhere within the test

5. click on the debug button shown above the test within the file.
   

6. click the continue button in the debugger controller until the end.

7. the cursor now should've moved to the top of the file.

>>>> Sample Code <<<<<<

import 'package:dart_code_test_bug/dart_code_test_bug.dart';
import 'package:test/test.dart';

/* 

LONG COMMENT TO SIMULATE THE BUG 


Jump to line 100 

























































































 */

void main() {
  test('calculate', () {
    try {
      expect(true, false);
    } on FormatException catch (e) {
      //
    }
  });
}

Expected behavior

I expect the cursor to stay in its place -- it's inconvenient to keep scrolling back after each run especially in large test files.

Please complete the following information:

• Operating System and version: 12.6 (21G115)
• VS Code version: 1.81.1
• Dart extension version: v3.70.0
• Dart/Flutter SDK version: Dart SDK version: 3.1.0 (stable) (Tue Aug 15 21:33:36 2023 +0000) on "macos_x64"

[DanTup]

I can reproduce this when debugging and an exception occurs. The exception breaks here:

And then clicking continue causes it to pause on the next frame up here:

I think this is because tokenPos in topFrame is -1 (see below). However, there is a function which has a valid location. I wonder whether the -1 is a bug or not - and if it's not, whether it's valid to use the location from function. I'll do some digging.

That said - even with this fixed so it doesn't jump to the top of the file, I don't know that it will solve this entire class of issue. If you hit an exception and click the Continue button, you're going to end up stepping up through a lot of code, so you may still end up in a different place to the test if the test wasn't the top stack frame.

"topFrame": {
	"type": "Frame",
	"kind": "Regular",
	"location": {
		"type": "SourceLocation",
		"script": {
			"type": "@Script",
			"fixedId": true,
			"id": "libraries/@18177300/scripts/file%3A%2F%2F%2FC%3A%2FDev%2FTest%2520Projects%2Fdart_sample%2Ftest%2Fdart_sample_test.dart/18a17861956",
			"uri": "file:///C:/Dev/Test%20Projects/dart_sample/test/dart_sample_test.dart"
		},
		"tokenPos": -1
	},
	"function": {
		"type": "@Function",
		"fixedId": true,
		"id": "libraries/@18177300/closures/47",
		"name": "<anonymous closure>",
		"static": true,
		"const": false,
		"implicit": false,
		"abstract": false,
		"location": {
			"type": "SourceLocation",
			"script": {
				"type": "@Script",
				"fixedId": true,
				"id": "libraries/@18177300/scripts/file%3A%2F%2F%2FC%3A%2FDev%2FTest%2520Projects%2Fdart_sample%2Ftest%2Fdart_sample_test.dart/18a17861956",
				"uri": "file:///C:/Dev/Test%20Projects/dart_sample/test/dart_sample_test.dart"
			},
			"tokenPos": 218,
			"endTokenPos": 315,
			"line": 101,
			"column": 21
		}
	},

[DanTup]

https://dart-review.googlesource.com/c/sdk/+/324522

[DanTup]

Fixed by dart-lang/sdk@a780653. The change ships in the SDK, not the VS Code extension.