Fixes #20757: Detect overlapping ranges in the extension host, no need to call into renderer process to find out the edits are illegal

extensions/vscode-api-tests/src/editor.test.ts

@@ -178,4 +178,23 @@ suite('editor tests', () => {
 			return Promise.resolve();
 		});
 	});
+
+	test('issue #20757: Overlapping ranges are not allowed!', () => {
+		return withRandomFileEditor('Hello world!\n\tHello world!', (editor, doc) => {
+			return editor.edit((builder) => {
+				// create two edits that overlap (i.e. are illegal)
+				builder.replace(new Range(0, 0, 0, 2), 'He');
+				builder.replace(new Range(0, 1, 0, 3), 'el');
+			}).then(
+
+				(applied) => {
+					assert.ok(false, 'edit with overlapping ranges should fail');
+				},
+
+				(err) => {
+					assert.ok(true, 'edit with overlapping ranges should fail');
+				}
+			);
+		});
+	});
 });