src/vs/workbench/contrib/comments/browser/commentsEditorContribution.ts/getActiveEditor
export function getActiveEditor(accessor: ServicesAccessor): IActiveCodeEditor | null {
	let activeTextEditorControl = accessor.get(IEditorService).activeTextEditorControl;

	if (isDiffEditor(activeTextEditorControl)) {
		if (activeTextEditorControl.getOriginalEditor().hasTextFocus()) {
			activeTextEditorControl = activeTextEditorControl.getOriginalEditor();
		} else {
			activeTextEditorControl = activeTextEditorControl.getModifiedEditor();
		}
	}

	if (!isCodeEditor(activeTextEditorControl) || !activeTextEditorControl.hasModel()) {
		return null;
	}

	return activeTextEditorControl;
}