Multiple DebugEditorModels for same URI lead to stack overflow

[colin-grant-work]

Bug Description:

If two editors are open for the same file, a number of issues arise related to breakpoint management due to the fact that both editors have their own DebugEditorModels.

Steps to Reproduce:

1. Open an editor.
2. Open a second instance (Ctrl+\)
3. Add a breakpoint.
4. Right click on the breakpoint decoration in the first editor and say 'Edit Breakpoint'
5. Observe that the breakpoint editor opens in the second editor.
6. Move the breakpoint up or down a few lines by adding or removing content from the second editor.
7. Observe hundreds of warnings about calling deltaDecorations recursively, as well as, possibly, a freeze and numerous stack overflow warnings.

Additional Information

There are two related issues. A DebugEditorModel is supposed to ignore events that originate from itself, which is the import of the check for this.updatingDecorations here:

theia/packages/debug/src/browser/editor/debug-editor-model.ts

Lines 308 to 320 in fe8e4c1

	protected areBreakpointsAffected(): boolean {
	if (this.updatingDecorations || !this.editor.getControl().getModel()) {
	return false;
	}
	for (const decoration of this.breakpointDecorations) {
	const range = this.editor.getControl().getModel()!.getDecorationRange(decoration);
	const oldRange = this.breakpointRanges.get(decoration)!;
	if (!range || !range.equalsRange(oldRange)) {
	return true;
	}
	}
	return false;
	}

But if another editor is active for the same URI, then each will trigger the other to check its breakpoints and eventually emit a new change event.

Relatedly, in the DebugEditorService, a new model is created for every editor, regardless of whether a model exists for that URI. This may also lead to undisposed DebugEditorModels.

theia/packages/debug/src/browser/editor/debug-editor-service.ts

Lines 61 to 73 in fe8e4c1

	protected push(widget: EditorWidget): void {
	const { editor } = widget;
	if (!(editor instanceof MonacoEditor)) {
	return;
	}
	const uri = editor.getControl().getModel()!.uri.toString();
	const debugModel = this.factory(editor);
	this.models.set(uri, debugModel);
	editor.getControl().onDidDispose(() => {
	debugModel.dispose();
	this.models.delete(uri);
	});
	}

• Operating System: RHEL 7
• Theia Version: fe8e4c1

[colin-grant-work]

The behavior seems to be quite bad in Firefox; it's hard to reproduce steps 6-7 at all in Chrome.