feat(core): add Deno.core.setPromiseHooks (#15475)

4 files changed, 197 insertions, 0 deletions

diff --git a/cli/tests/unit/promise_hooks_test.ts b/cli/tests/unit/promise_hooks_test.ts
new file mode 100644
index 000000000..647fa98cb
--- /dev/null
+++ b/cli/tests/unit/promise_hooks_test.ts
@@ -0,0 +1,109 @@
+// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
+
+import { assertEquals } from "./test_util.ts";
+
+function monitorPromises(outputArray: string[]) {
+  const promiseIds = new Map<Promise<unknown>, string>();
+
+  function identify(promise: Promise<unknown>) {
+    if (!promiseIds.has(promise)) {
+      promiseIds.set(promise, "p" + (promiseIds.size + 1));
+    }
+    return promiseIds.get(promise);
+  }
+
+  // @ts-ignore: Deno.core allowed
+  Deno.core.setPromiseHooks(
+    (promise: Promise<unknown>, parentPromise?: Promise<unknown>) => {
+      outputArray.push(
+        `init ${identify(promise)}` +
+          (parentPromise ? ` from ${identify(parentPromise)}` : ``),
+      );
+    },
+    (promise: Promise<unknown>) => {
+      outputArray.push(`before ${identify(promise)}`);
+    },
+    (promise: Promise<unknown>) => {
+      outputArray.push(`after ${identify(promise)}`);
+    },
+    (promise: Promise<unknown>) => {
+      outputArray.push(`resolve ${identify(promise)}`);
+    },
+  );
+}
+
+Deno.test(async function promiseHookBasic() {
+  // Bogus await here to ensure any pending promise resolution from the
+  // test runtime has a chance to run and avoid contaminating our results.
+  await Promise.resolve(null);
+
+  const hookResults: string[] = [];
+  monitorPromises(hookResults);
+
+  async function asyncFn() {
+    await Promise.resolve(15);
+    await Promise.resolve(20);
+    Promise.reject(new Error()).catch(() => {});
+  }
+
+  // The function above is equivalent to:
+  //   function asyncFn() {
+  //     return new Promise(resolve => {
+  //       Promise.resolve(15).then(() => {
+  //         Promise.resolve(20).then(() => {
+  //           Promise.reject(new Error()).catch(() => {});
+  //           resolve();
+  //         });
+  //       });
+  //     });
+  //   }
+
+  await asyncFn();
+
+  assertEquals(hookResults, [
+    "init p1", // Creates the promise representing the return of `asyncFn()`.
+    "init p2", // Creates the promise representing `Promise.resolve(15)`.
+    "resolve p2", // The previous promise resolves to `15` immediately.
+    "init p3 from p2", // Creates the promise that is resolved after the first `await` of the function. Equivalent to `p2.then(...)`.
+    "init p4 from p1", // The resolution above gives time for other pending code to run. Creates the promise that is resolved
+    // from the `await` at `await asyncFn()`, the last code to run. Equivalent to `asyncFn().then(...)`.
+    "before p3", // Begins executing the code after `await Promise.resolve(15)`.
+    "init p5", // Creates the promise representing `Promise.resolve(20)`.
+    "resolve p5", // The previous promise resolves to `20` immediately.
+    "init p6 from p5", // Creates the promise that is resolved after the second `await` of the function. Equivalent to `p5.then(...)`.
+    "resolve p3", // The promise representing the code right after the first await is marked as resolved.
+    "after p3", // We are now after the resolution code of the promise above.
+    "before p6", // Begins executing the code after `await Promise.resolve(20)`.
+    "init p7", // Creates a new promise representing `Promise.reject(new Error())`.
+    "resolve p7", // This promise is "resolved" immediately to a rejection with an error instance.
+    "init p8 from p7", // Creates a new promise for the `.catch` of the previous promise.
+    "resolve p1", // At this point the promise of the function is resolved.
+    "resolve p6", // This concludes the resolution of the code after `await Promise.resolve(20)`.
+    "after p6", // We are now after the resolution code of the promise above.
+    "before p8", // The `.catch` block is pending execution, it begins to execute.
+    "resolve p8", // It does nothing and resolves to `undefined`.
+    "after p8", // We are after the resolution of the `.catch` block.
+    "before p4", // Now we begin the execution of the code that happens after `await asyncFn();`.
+  ]);
+});
+
+Deno.test(async function promiseHookMultipleConsumers() {
+  const hookResultsFirstConsumer: string[] = [];
+  const hookResultsSecondConsumer: string[] = [];
+
+  monitorPromises(hookResultsFirstConsumer);
+  monitorPromises(hookResultsSecondConsumer);
+
+  async function asyncFn() {
+    await Promise.resolve(15);
+    await Promise.resolve(20);
+    Promise.reject(new Error()).catch(() => {});
+  }
+  await asyncFn();
+
+  // Two invocations of `setPromiseHooks` should yield the exact same results, in the same order.
+  assertEquals(
+    hookResultsFirstConsumer,
+    hookResultsSecondConsumer,
+  );
+});
diff --git a/core/01_core.js b/core/01_core.js
index 08f839c98..655b4219e 100644
--- a/core/01_core.js
+++ b/core/01_core.js
@@ -12,6 +12,7 @@
     Map,
     Array,
     ArrayPrototypeFill,
+    ArrayPrototypePush,
     ArrayPrototypeMap,
     ErrorCaptureStackTrace,
     Promise,
@@ -266,6 +267,43 @@
   }
   const InterruptedPrototype = Interrupted.prototype;
 
+  const promiseHooks = {
+    init: [],
+    before: [],
+    after: [],
+    resolve: [],
+    hasBeenSet: false,
+  };
+
+  function setPromiseHooks(init, before, after, resolve) {
+    if (init) ArrayPrototypePush(promiseHooks.init, init);
+    if (before) ArrayPrototypePush(promiseHooks.before, before);
+    if (after) ArrayPrototypePush(promiseHooks.after, after);
+    if (resolve) ArrayPrototypePush(promiseHooks.resolve, resolve);
+
+    if (!promiseHooks.hasBeenSet) {
+      promiseHooks.hasBeenSet = true;
+
+      ops.op_set_promise_hooks((promise, parentPromise) => {
+        for (let i = 0; i < promiseHooks.init.length; ++i) {
+          promiseHooks.init[i](promise, parentPromise);
+        }
+      }, (promise) => {
+        for (let i = 0; i < promiseHooks.before.length; ++i) {
+          promiseHooks.before[i](promise);
+        }
+      }, (promise) => {
+        for (let i = 0; i < promiseHooks.after.length; ++i) {
+          promiseHooks.after[i](promise);
+        }
+      }, (promise) => {
+        for (let i = 0; i < promiseHooks.resolve.length; ++i) {
+          promiseHooks.resolve[i](promise);
+        }
+      });
+    }
+  }
+
   // Extra Deno.core.* exports
   const core = ObjectAssign(globalThis.Deno.core, {
     opAsync,
@@ -286,6 +324,7 @@
     refOp,
     unrefOp,
     setReportExceptionCallback,
+    setPromiseHooks,
     close: (rid) => ops.op_close(rid),
     tryClose: (rid) => ops.op_try_close(rid),
     read: opAsync.bind(null, "op_read"),
diff --git a/core/lib.deno_core.d.ts b/core/lib.deno_core.d.ts
index c5662794a..7e46d0f14 100644
--- a/core/lib.deno_core.d.ts
+++ b/core/lib.deno_core.d.ts
@@ -164,5 +164,26 @@ declare namespace Deno {
      * enabled.
      */
     const opCallTraces: Map<number, OpCallTrace>;
+
+    /**
+     * Adds a callback for the given Promise event. If this function is called
+     * multiple times, the callbacks are called in the order they were added.
+     * - `init_hook` is called when a new promise is created. When a new promise
+     *   is created as part of the chain in the case of `Promise.then` or in the
+     *   intermediate promises created by `Promise.{race, all}`/`AsyncFunctionAwait`,
+     *   we pass the parent promise otherwise we pass undefined.
+     * - `before_hook` is called at the beginning of the promise reaction.
+     * - `after_hook` is called at the end of the promise reaction.
+     * - `resolve_hook` is called at the beginning of resolve or reject function.
+     */
+    function setPromiseHooks(
+      init_hook?: (
+        promise: Promise<unknown>,
+        parentPromise?: Promise<unknown>,
+      ) => void,
+      before_hook?: (promise: Promise<unknown>) => void,
+      after_hook?: (promise: Promise<unknown>) => void,
+      resolve_hook?: (promise: Promise<unknown>) => void,
+    ): void;
   }
 }
diff --git a/core/ops_builtin_v8.rs b/core/ops_builtin_v8.rs
index 3900c0641..e626c03c1 100644
--- a/core/ops_builtin_v8.rs
+++ b/core/ops_builtin_v8.rs
@@ -37,6 +37,7 @@ pub(crate) fn init_builtins_v8() -> Vec<OpDecl> {
     op_decode::decl(),
     op_serialize::decl(),
     op_deserialize::decl(),
+    op_set_promise_hooks::decl(),
     op_get_promise_details::decl(),
     op_get_proxy_details::decl(),
     op_memory_usage::decl(),
@@ -575,6 +576,33 @@ fn op_get_promise_details<'a>(
   }
 }
 
+#[op(v8)]
+fn op_set_promise_hooks<'a>(
+  scope: &mut v8::HandleScope<'a>,
+  init_cb: serde_v8::Value,
+  before_cb: serde_v8::Value,
+  after_cb: serde_v8::Value,
+  resolve_cb: serde_v8::Value,
+) -> Result<(), Error> {
+  let init_hook_global = to_v8_fn(scope, init_cb)?;
+  let before_hook_global = to_v8_fn(scope, before_cb)?;
+  let after_hook_global = to_v8_fn(scope, after_cb)?;
+  let resolve_hook_global = to_v8_fn(scope, resolve_cb)?;
+  let init_hook = v8::Local::new(scope, init_hook_global);
+  let before_hook = v8::Local::new(scope, before_hook_global);
+  let after_hook = v8::Local::new(scope, after_hook_global);
+  let resolve_hook = v8::Local::new(scope, resolve_hook_global);
+
+  scope.get_current_context().set_promise_hooks(
+    init_hook,
+    before_hook,
+    after_hook,
+    resolve_hook,
+  );
+
+  Ok(())
+}
+
 // Based on https://github.com/nodejs/node/blob/1e470510ff74391d7d4ec382909ea8960d2d2fbc/src/node_util.cc
 // Copyright Joyent, Inc. and other Node contributors.
 //