Populate function descriptions in RemoteObject

Summary:
bypass-github-export-checks

Changelog: [Internal]

[`Runtime.RemoteObject`](https://cdpstatus.reactnative.dev/devtools-protocol/tot/Runtime#type-RemoteObject) 's `description` property is a string, but in
the case of functions, V8 populates it with the result of [toString][1]
and Chrome DevTools uses a [series of regexes][2] to extract structured
information about the function.

Here, we add similar behaviour to Hermes to enable the various Chrome
DevTools UI features that are powered by function descriptions, such as
showing function names on hover and in object previews.

[1]: https://source.chromium.org/chromium/chromium/src/+/main:v8/src/debug/debug-interface.cc;l=138-174;drc=42debe0b0e6bf90175dd0d121eb0e7dc11a6d29c
[2]: https://github.com/facebookexperimental/rn-chrome-devtools-frontend/blob/9a23d4c7c4c2d1a3d9e913af38d6965f474c4284/front_end/ui/legacy/components/object_ui/ObjectPropertiesSection.ts#L311-L391

Reviewed By: dannysu

Differential Revision: D56343190

fbshipit-source-id: a7ef5f09c98f34f486c4db2d4af192f10811d671

packages/react-native/ReactCommon/jsinspector-modern/tests/FollyDynamicMatchers.h

@@ -77,6 +77,24 @@ MATCHER_P2(
   return false;
 }
 
+/**
+ * A higher-order matcher that applies an inner matcher to the string value of
+ * a folly::dynamic.
+ */
+MATCHER_P(
+    DynamicString,
+    innerMatcher,
+    std::string{"string value "} +
+        testing::DescribeMatcher<std::string>(innerMatcher, negation)) {
+  using namespace ::testing;
+  using namespace folly_dynamic_matchers_utils;
+  if (!arg.isString()) {
+    *result_listener << "is not a string";
+    return false;
+  }
+  return ExplainMatchResult(innerMatcher, arg.getString(), result_listener);
+}
+
 /**
  * A user-defined literal for constructing a folly::dynamic from a JSON
  * string. Not technically specific to GMock, but convenient to have in a test

packages/react-native/ReactCommon/jsinspector-modern/tests/JsiIntegrationTest.cpp

@@ -546,6 +546,27 @@ TYPED_TEST(JsiIntegrationHermesTest, ScriptParsedExactlyOnce) {
                                })");
 }
 
+TYPED_TEST(JsiIntegrationHermesTest, FunctionDescriptionIncludesName) {
+  // See
+  // https://github.com/facebookexperimental/rn-chrome-devtools-frontend/blob/9a23d4c7c4c2d1a3d9e913af38d6965f474c4284/front_end/ui/legacy/components/object_ui/ObjectPropertiesSection.ts#L311-L391
+
+  this->connect();
+
+  InSequence s;
+
+  this->expectMessageFromPage(JsonParsed(AllOf(
+      AtJsonPtr("/id", 1),
+      AtJsonPtr("/result/result/type", "function"),
+      AtJsonPtr(
+          "/result/result/description",
+          DynamicString(StartsWith("function foo() {"))))));
+  this->toPage_->sendMessage(R"({
+                               "id": 1,
+                               "method": "Runtime.evaluate",
+                               "params": {"expression": "(function foo() {Math.random()});"}
+                             })");
+}
+
 #pragma endregion // AllHermesVariants
 
 } // namespace facebook::react::jsinspector_modern