[inspector] Improve regular expression printing

Prior to this patch, `new RegExp('a/b')` logs the following in
the DevTools Console:

    /a/b/

This is syntactically invalid.

This patch fixes this while simplifying regular expression printing
in general by leveraging `RegExp#toString`, instead of duplicating
the logic on the inspector side. This is possible thanks to the recent
work on making `RegExp#toString` more robust (v8:1982).

Bug: chromium:1202013, v8:1982
Change-Id: I14ccc1892f4a99361ad170fea608ace630740991
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2848463
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74169}

src/inspector/value-mirror.cc

@@ -195,22 +195,19 @@ String16 descriptionForPrimitiveType(v8::Local<v8::Context> context,
   return String16();
 }
 
-String16 descriptionForRegExp(v8::Isolate* isolate,
+String16 descriptionForObject(v8::Isolate* isolate,
+                              v8::Local<v8::Object> object) {
+  return toProtocolString(isolate, object->GetConstructorName());
+}
+
+String16 descriptionForRegExp(v8::Local<v8::Context> context,
                               v8::Local<v8::RegExp> value) {
-  String16Builder description;
-  description.append('/');
-  description.append(toProtocolString(isolate, value->GetSource()));
-  description.append('/');
-  v8::RegExp::Flags flags = value->GetFlags();
-  if (flags & v8::RegExp::Flags::kHasIndices) description.append('d');
-  if (flags & v8::RegExp::Flags::kGlobal) description.append('g');
-  if (flags & v8::RegExp::Flags::kIgnoreCase) description.append('i');
-  if (flags & v8::RegExp::Flags::kLinear) description.append('l');
-  if (flags & v8::RegExp::Flags::kMultiline) description.append('m');
-  if (flags & v8::RegExp::Flags::kDotAll) description.append('s');
-  if (flags & v8::RegExp::Flags::kUnicode) description.append('u');
-  if (flags & v8::RegExp::Flags::kSticky) description.append('y');
-  return description.toString();
+  v8::Isolate* isolate = context->GetIsolate();
+  v8::Local<v8::String> description;
+  if (!value->ToString(context).ToLocal(&description)) {
+    return descriptionForObject(isolate, value);
+  }
+  return toProtocolString(isolate, description);
 }
 
 enum class ErrorType { kNative, kClient };
@@ -268,11 +265,6 @@ String16 descriptionForError(v8::Local<v8::Context> context,
   return description + stackWithoutMessage;
 }
 
-String16 descriptionForObject(v8::Isolate* isolate,
-                              v8::Local<v8::Object> object) {
-  return toProtocolString(isolate, object->GetConstructorName());
-}
-
 String16 descriptionForDate(v8::Local<v8::Context> context,
                             v8::Local<v8::Date> date) {
   v8::Isolate* isolate = context->GetIsolate();
@@ -1605,7 +1597,7 @@ std::unique_ptr<ValueMirror> ValueMirror::create(v8::Local<v8::Context> context,
   if (value->IsRegExp()) {
     return std::make_unique<ObjectMirror>(
         value, RemoteObject::SubtypeEnum::Regexp,
-        descriptionForRegExp(isolate, value.As<v8::RegExp>()));
+        descriptionForRegExp(context, value.As<v8::RegExp>()));
   }
   if (value->IsProxy()) {
     return std::make_unique<ObjectMirror>(

test/inspector/runtime/remote-object-expected.txt

@@ -487,6 +487,16 @@ Running test: testRegExp
         type : object
     }
 }
+'new RegExp('foo/bar')', returnByValue: false, generatePreview: false
+{
+    result : {
+        className : RegExp
+        description : /foo\/bar/
+        objectId : <objectId>
+        subtype : regexp
+        type : object
+    }
+}
 'var re = new RegExp('\w+', 'g');
         re.prop = 32;
         re', returnByValue: false, generatePreview: true

test/inspector/runtime/remote-object.js

@@ -227,6 +227,9 @@ InspectorTest.runAsyncTestSuite([
     InspectorTest.logMessage((await evaluate({
       expression: `new RegExp('\\w+', 'g')`,
     })).result);
+    InspectorTest.logMessage((await evaluate({
+      expression: `new RegExp('foo/bar')`
+    })).result);
     InspectorTest.logMessage((await evaluate({
       expression: `var re = new RegExp('\\w+', 'g');
         re.prop = 32;