Integration test for CDPAgent reentrancy bugs

Summary:
Changelog: [Internal]

Adds a regression test for a Hermes CDPAgent bug using `JsiIntegrationTest`. See details in comments.

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Reviewed By: huntie

Differential Revision: D54890188

fbshipit-source-id: 325a32b83b145d2d35f99feaef9988028f15f196

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

@@ -620,6 +620,66 @@ TYPED_TEST(JsiIntegrationHermesModernTest, ResolveBreakpointAfterReload) {
       scriptInfo->value()["params"]["scriptId"]);
 }
 
+TYPED_TEST(JsiIntegrationHermesModernTest, CDPAgentReentrancyRegressionTest) {
+  this->connect();
+
+  // TODO(moti): Add an InSequence guard here once Hermes processes the messages
+  // in the order they were received.
+
+  this->inspectorExecutor_([&]() {
+    // Tasks scheduled on our executor here will be executed when this lambda
+    // returns. This is integral to the bug we're trying to reproduce, so we
+    // place the EXPECT_* calls at the end of the lambda body to ensure the
+    // test fails if we get eager (unexpected) responses.
+
+    // 1. Cause CDPAgent to schedule a task on the JS executor to process the
+    //    message. The task is simultaneously scheduled as an interrupt on the
+    //    JS VM (but will be called via the executor, since the interpreter is
+    //    idle at the moment).
+    this->toPage_->sendMessage(R"({
+                                   "id": 1,
+                                   "method": "Runtime.evaluate",
+                                   "params": {"expression": "1 + 2"}
+                                 })");
+
+    // 2. Cause CDPAgent to schedule another task+interrupt.
+    this->toPage_->sendMessage(R"({
+                                   "id": 2,
+                                   "method": "Runtime.evaluate",
+                                   "params": {"expression": "3 + 4"}
+                                 })");
+
+    // 3. When the first scheduled task runs (via the executor), it enters the
+    //    interpreter to evaluate the expression, at which point the
+    //    interpreter begins processing interrupts and enters the second task.
+    //    This used to trigger two distinct bugs in CDPAgent:
+    //      - The first task would be triggered twice due to a race condition
+    //        between the executor and the interrupt handler. (D54771697)
+    //      - The second task would deadlock due to the first task holding a
+    //        lock preventing any other CDPAgent tasks from running. (D54838179)
+
+    this->expectMessageFromPage(JsonEq(R"({
+                                            "id": 1,
+                                            "result": {
+                                              "result": {
+                                                "type": "number",
+                                                "value": 3
+                                              }
+                                            }
+                                          })"));
+
+    this->expectMessageFromPage(JsonEq(R"({
+                                            "id": 2,
+                                            "result": {
+                                              "result": {
+                                                "type": "number",
+                                                "value": 7
+                                              }
+                                            }
+                                          })"));
+  });
+}
+
 #pragma endregion // ModernHermesVariants
 
 } // namespace facebook::react::jsinspector_modern