util: add callbackify

Add `util.callbackify(function)` for creating callback style functions
from functions returning a `Thenable`

PR-URL: https://github.com/nodejs/node/pull/12712
Fixes: https://github.com/nodejs/CTC/issues/109
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Teddy Katz <teddy.katz@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

1 files changed, 227 insertions, 0 deletions

diff --git a/test/parallel/test-util-callbackify.js b/test/parallel/test-util-callbackify.js
new file mode 100644
index 0000000000..fa793d4a7f
--- /dev/null
+++ b/test/parallel/test-util-callbackify.js
@@ -0,0 +1,227 @@
+'use strict';
+const common = require('../common');
+
+// This test checks that the semantics of `util.callbackify` are as described in
+// the API docs
+
+const assert = require('assert');
+const { callbackify } = require('util');
+const { join } = require('path');
+const { execFile } = require('child_process');
+const fixtureDir = join(common.fixturesDir, 'uncaught-exceptions');
+const values = [
+  'hello world',
+  null,
+  undefined,
+  false,
+  0,
+  {},
+  { key: 'value' },
+  Symbol('I am a symbol'),
+  function ok() {},
+  ['array', 'with', 4, 'values'],
+  new Error('boo')
+];
+
+{
+  // Test that the resolution value is passed as second argument to callback
+  for (const value of values) {
+    // Test and `async function`
+    async function asyncFn() {
+      return await Promise.resolve(value);
+    }
+
+    const cbAsyncFn = callbackify(asyncFn);
+    cbAsyncFn(common.mustCall((err, ret) => {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+    }));
+
+    // Test Promise factory
+    function promiseFn() {
+      return Promise.resolve(value);
+    }
+
+    const cbPromiseFn = callbackify(promiseFn);
+    cbPromiseFn(common.mustCall((err, ret) => {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+    }));
+
+    // Test Thenable
+    function thenableFn() {
+      return {
+        then(onRes, onRej) {
+          onRes(value);
+        }
+      };
+    }
+
+    const cbThenableFn = callbackify(thenableFn);
+    cbThenableFn(common.mustCall((err, ret) => {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+    }));
+  }
+}
+
+{
+  // Test that rejection reason is passed as first argument to callback
+  for (const value of values) {
+    // Test an `async function`
+    async function asyncFn() {
+      return await Promise.reject(value);
+    }
+
+    const cbAsyncFn = callbackify(asyncFn);
+    cbAsyncFn(common.mustCall((err, ret) => {
+      assert.strictEqual(ret, undefined);
+      if (err instanceof Error) {
+        if ('reason' in err) {
+          assert(!value);
+          assert.strictEqual(err.code, 'FALSY_VALUE_REJECTION');
+          assert.strictEqual(err.reason, value);
+        } else {
+          assert.strictEqual(String(value).endsWith(err.message), true);
+        }
+      } else {
+        assert.strictEqual(err, value);
+      }
+    }));
+
+    // test a Promise factory
+    function promiseFn() {
+      return Promise.reject(value);
+    }
+
+    const cbPromiseFn = callbackify(promiseFn);
+    cbPromiseFn(common.mustCall((err, ret) => {
+      assert.strictEqual(ret, undefined);
+      if (err instanceof Error) {
+        if ('reason' in err) {
+          assert(!value);
+          assert.strictEqual(err.code, 'FALSY_VALUE_REJECTION');
+          assert.strictEqual(err.reason, value);
+        } else {
+          assert.strictEqual(String(value).endsWith(err.message), true);
+        }
+      } else {
+        assert.strictEqual(err, value);
+      }
+    }));
+
+    // Test Thenable
+    function thenableFn() {
+      return {
+        then(onRes, onRej) {
+          onRej(value);
+        }
+      };
+    }
+
+    const cbThenableFn = callbackify(thenableFn);
+    cbThenableFn(common.mustCall((err, ret) => {
+      assert.strictEqual(ret, undefined);
+      if (err instanceof Error) {
+        if ('reason' in err) {
+          assert(!value);
+          assert.strictEqual(err.code, 'FALSY_VALUE_REJECTION');
+          assert.strictEqual(err.reason, value);
+        } else {
+          assert.strictEqual(String(value).endsWith(err.message), true);
+        }
+      } else {
+        assert.strictEqual(err, value);
+      }
+    }));
+  }
+}
+
+{
+  // Test that arguments passed to callbackified function are passed to original
+  for (const value of values) {
+    async function asyncFn(arg) {
+      assert.strictEqual(arg, value);
+      return await Promise.resolve(arg);
+    }
+
+    const cbAsyncFn = callbackify(asyncFn);
+    cbAsyncFn(value, common.mustCall((err, ret) => {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+    }));
+
+    function promiseFn(arg) {
+      assert.strictEqual(arg, value);
+      return Promise.resolve(arg);
+    }
+
+    const cbPromiseFn = callbackify(promiseFn);
+    cbPromiseFn(value, common.mustCall((err, ret) => {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+    }));
+  }
+}
+
+{
+  // Test that `this` binding is the same for callbackified and original
+  for (const value of values) {
+    const iAmThis = {
+      fn(arg) {
+        assert.strictEqual(this, iAmThis);
+        return Promise.resolve(arg);
+      },
+    };
+    iAmThis.cbFn = callbackify(iAmThis.fn);
+    iAmThis.cbFn(value, common.mustCall(function(err, ret) {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+      assert.strictEqual(this, iAmThis);
+    }));
+
+    const iAmThat = {
+      async fn(arg) {
+        assert.strictEqual(this, iAmThat);
+        return await Promise.resolve(arg);
+      },
+    };
+    iAmThat.cbFn = callbackify(iAmThat.fn);
+    iAmThat.cbFn(value, common.mustCall(function(err, ret) {
+      assert.ifError(err);
+      assert.strictEqual(ret, value);
+      assert.strictEqual(this, iAmThat);
+    }));
+  }
+}
+
+{
+  // Test that callback that throws emits an `uncaughtException` event
+  const fixture = join(fixtureDir, 'callbackify1.js');
+  execFile(
+    process.execPath,
+    [fixture],
+    common.mustCall((err, stdout, stderr) => {
+      assert.strictEqual(err.code, 1);
+      assert.strictEqual(Object.getPrototypeOf(err).name, 'Error');
+      assert.strictEqual(stdout, '');
+      const errLines = stderr.trim().split(/[\r\n]+/g);
+      const errLine = errLines.find((l) => /^Error/.exec(l));
+      assert.strictEqual(errLine, `Error: ${fixture}`);
+    })
+  );
+}
+
+{
+  // Test that handled `uncaughtException` works and passes rejection reason
+  const fixture = join(fixtureDir, 'callbackify2.js');
+  execFile(
+    process.execPath,
+    [fixture],
+    common.mustCall((err, stdout, stderr) => {
+      assert.ifError(err);
+      assert.strictEqual(stdout.trim(), fixture);
+      assert.strictEqual(stderr, '');
+    })
+  );
+}