Hide more temporary variables when debugging (#2445)

Some variables created by DDC that are not present in the
original source code were being shown by the debugger in the
local scope.

Update the regular expression used to detect temporary variable names.
It has been simplified to: if the variable starts with 't$' or contains
'$35' then it should be hidden.

DDC names it's temporary variables to start with the characters `t$`.
Hiding all of these does hide some valid variable names that could
appear in the original source, but that is the status quo and not
being changed here. In addition some names that are created by the
CFE and added to the program contain an illegal character '#' which
DDC replaces as '$35'. Variables with this sequence in the name can't
appear in the original source so we hide them as well.

This should hide variables synthetically added to support late local
variables.

Author: nshahan

dwds/CHANGELOG.md

@@ -4,6 +4,8 @@
 - Respect the value of `pause_isolates_on_start` during page-refreshes. - [#2431](https://github.com/dart-lang/webdev/pull/2431)
 - Fix issue where DAP clients wouldn't resume after a restart. - [#2441](https://github.com/dart-lang/webdev/pull/2441)
 - Add implementation for the VM Service's `getFlagList` API. - [#2438](https://github.com/dart-lang/webdev/pull/2438)
+- Hide more variables from the local scope when debugging. These variables were synthetically added by the compiler to
+  support late local variables and don't appear in the original source code. - [#2445](https://github.com/dart-lang/webdev/pull/2445)
 
 ## 24.0.0
 

dwds/lib/src/debugging/dart_scope.dart

@@ -12,7 +12,15 @@ import 'package:webkit_inspection_protocol/webkit_inspection_protocol.dart';
 /// TODO(annagrin) - use an alternative way to identify
 /// synthetic variables.
 /// Issue: https://github.com/dart-lang/sdk/issues/44262
-final ddcTemporaryVariableRegExp = RegExp(r'^t(\$[0-9]*)+\w*$');
+final ddcTemporaryVariableRegExp = RegExp(
+    // Starts with t$
+    r'^t\$'
+    // followed by anything
+    r'.*'
+    // or,
+    r'|'
+    // anything that contains the sequence '$35'.
+    r'.*\$35.*');
 final ddcTemporaryTypeVariableRegExp = RegExp(r'^__t[\$\w*]+$');
 
 /// Temporary variable regex before SDK changes for patterns.

dwds/test/variable_scope_test.dart

@@ -71,6 +71,14 @@ void main() {
         ddcTemporaryVariableRegExp.hasMatch(r't$36$350$354$35isSet'),
         isTrue,
       );
+      expect(
+        ddcTemporaryVariableRegExp.hasMatch(r't$36$35variable$35isSet'),
+        isTrue,
+      );
+      expect(
+        ddcTemporaryVariableRegExp.hasMatch(r'synthetic$35variable'),
+        isTrue,
+      );
       expect(ddcTemporaryTypeVariableRegExp.hasMatch(r'__t$TL'), isTrue);
       expect(ddcTemporaryTypeVariableRegExp.hasMatch(r'__t$StringN'), isTrue);
       expect(
@@ -84,6 +92,7 @@ void main() {
       expect(ddcTemporaryVariableRegExp.hasMatch(r't10'), isFalse);
       expect(ddcTemporaryVariableRegExp.hasMatch(r't10foo'), isFalse);
       expect(ddcTemporaryVariableRegExp.hasMatch(r'ten'), isFalse);
+      expect(ddcTemporaryVariableRegExp.hasMatch(r'my$3635variable'), isFalse);
     });
   });