fix(ext/node): flesh out node:trace_events polyfill (#34216)

## Summary

The `node:trace_events` polyfill was a stub — `createTracing` returned
an
object with no `.enable`/`.disable` methods and `getEnabledCategories`
always returned `""`. This fleshes out the polyfill enough that the
four ignored compat tests now run end-to-end.

- `createTracing` validates input, returns a `Tracing` with `enabled` /
  `categories` properties and `enable()`/`disable()` methods, and emits
  the `>10` instances memory-leak warning.
- `getEnabledCategories()` returns `undefined` when no instance is
  enabled, otherwise the comma-joined union of every enabled instance's
  categories.
- `internalBinding('trace_events')` now exposes `trace(phase, cat, name,
id, scope)` and `getCategoryEnabledBuffer(cat)` (with refcount
  semantics) so fixtures going through `internal/test/binding` observe
  the same state as the public API.
- When `node.async_hooks` is enabled, `setTimeout` / `setImmediate` are
  wrapped to emit `b`/`e` events with `cat="node,node.async_hooks"`.
  On process exit each isolate writes its recorded events; workers
  write per-thread slice files in `cwd` and the main isolate aggregates
  them into a single `node_trace.${rotation}.log` so consumers see one
  combined log (matching Node's process-wide `TracingController`
  behavior).
- `--trace-event-categories` is now plumbed through `node_shim` →
  `child_process` as `DENO_NODE_TRACE_EVENT_CATEGORIES`. The node
  bootstrap (`01_require.js`) reads it in every isolate (main +
  workers), pre-enables the listed categories, and pushes the flag
  back onto `process.execArgv` so test fixtures that probe `execArgv`
  see the expected shape.

Enables in `tests/node_compat/config.jsonc`:

- `parallel/test-trace-events-api.js`
- `parallel/test-trace-events-async-hooks-dynamic.js`
- `parallel/test-trace-events-async-hooks-worker.js`
- `parallel/test-trace-events-get-category-enabled-buffer.js`

Closes denoland/orchid#136

## Test plan

- [x] `cargo test --test node_compat -- test-trace-events-api.js`
- [x] `cargo test --test node_compat --
test-trace-events-async-hooks-dynamic.js`
- [x] `cargo test --test node_compat --
test-trace-events-async-hooks-worker.js`
- [x] `cargo test --test node_compat --
test-trace-events-get-category-enabled-buffer.js`
- [x] `cargo test --test node_compat --
test-trace-events-dynamic-enable-workers-disabled.js` (already-passing
test still passes)
- [x] `cargo test -p node_shim` (127 tests pass)
- [x] `cargo clippy --bin deno`

---------

Co-authored-by: divybot <divybot@users.noreply.github.com>
Co-authored-by: Divy Srivastava <me@littledivy.com>

Author: divybot

ext/node/ops/node_cli_parser.rs

@@ -48,6 +48,9 @@ pub struct TranslatedArgs {
   pub use_openssl_ca: bool,
   /// Whether the child process needs npm process state
   pub needs_npm_process_state: bool,
+  /// Comma-separated trace event categories from --trace-event-categories,
+  /// to be propagated via DENO_NODE_TRACE_EVENT_CATEGORIES.
+  pub trace_event_categories: Option<String>,
 }
 
 /// Translate parsed Node.js CLI arguments to Deno CLI arguments.
@@ -76,12 +79,19 @@ fn translate_to_deno_args(
     }
   };
 
+  let trace_event_categories = if result.trace_event_categories.is_empty() {
+    None
+  } else {
+    Some(result.trace_event_categories)
+  };
+
   TranslatedArgs {
     deno_args: result.deno_args,
     node_options: result.node_options,
     ca_stores,
     use_openssl_ca,
     needs_npm_process_state: script_in_npm_package,
+    trace_event_categories,
   }
 }
 
@@ -109,6 +119,7 @@ pub fn op_node_translate_cli_args(
       ca_stores: None,
       use_openssl_ca: false,
       needs_npm_process_state: script_in_npm_package,
+      trace_event_categories: None,
     });
   }
 

ext/node/polyfills/01_require.js

@@ -5,6 +5,7 @@
 import { core, internals, primordials } from "ext:core/mod.js";
 import {
   op_fs_cwd,
+  op_get_env_no_permission_check,
   op_import_sync,
   op_import_sync_with_source,
   op_module_default_resolve,
@@ -3157,6 +3158,33 @@ function initialize(args) {
       nativeModuleExports["console"],
       nativeModuleExports["process"],
     );
+    // Pre-enable any trace event categories requested via the spawning
+    // process's --trace-event-categories flag (propagated as an env var by
+    // child_process). This must run in every isolate, including workers,
+    // so that node.async_hooks tracing covers worker threads too.
+    const traceCategoriesEnv = op_get_env_no_permission_check(
+      "DENO_NODE_TRACE_EVENT_CATEGORIES",
+    );
+    if (traceCategoriesEnv) {
+      const traceEvents = core.loadExtScript("ext:deno_node/trace_events.ts");
+      const categories = traceCategoriesEnv.split(",").filter((c) =>
+        c.length > 0
+      );
+      if (categories.length > 0) {
+        // Surface the flag through process.execArgv so test fixtures that
+        // probe it (e.g. node's test-trace-events-api) see the same shape
+        // they would in Node.
+        const proc = nativeModuleExports["process"];
+        if (proc && Array.isArray(proc.execArgv)) {
+          proc.execArgv.push("--trace-event-categories", traceCategoriesEnv);
+        }
+        try {
+          traceEvents.createTracing({ categories }).enable();
+        } catch {
+          // Invalid categories must not block startup.
+        }
+      }
+    }
   } else {
     internals.__bootstrapNodeProcess(
       undefined,

ext/node/polyfills/child_process.ts

@@ -205,6 +205,12 @@ function fork(
     } else if (options.env?.DENO_NODE_USE_OPENSSL_CA) {
       delete options.env.DENO_NODE_USE_OPENSSL_CA;
     }
+    if (result.traceEventCategories) {
+      options.env = {
+        ...(options.env ?? process.env),
+        DENO_NODE_TRACE_EVENT_CATEGORIES: result.traceEventCategories,
+      };
+    }
   }
 
   if (typeof options.stdio === "string") {

ext/node/polyfills/internal/child_process.ts

@@ -1496,6 +1496,9 @@ function buildCommand(
     } else {
       delete env.DENO_NODE_USE_OPENSSL_CA;
     }
+    if (result.traceEventCategories) {
+      env.DENO_NODE_TRACE_EVENT_CATEGORIES = result.traceEventCategories;
+    }
 
     // Update NODE_OPTIONS if needed
     if (result.nodeOptions.length > 0) {