test, tools: add common.noop and common.mustNotCall lint rule

test/.eslintrc.yaml

@@ -9,5 +9,6 @@ rules:
   # Custom rules in tools/eslint-rules
   prefer-assert-iferror: 2
   prefer-assert-methods: 2
+  prefer-common-mustnotcall: 2
   ## common module is mandatory in tests
   required-modules: [2, common]

test/README.md

@@ -324,7 +324,7 @@ Gets IP of localhost
 
 Array of IPV6 hosts.
 
-### mustCall(fn[, expected])
+### mustCall([fn][, expected])
 * fn [<Function>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function)
 * expected [<Number>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type) default = 1
 * return [<Function>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function)
@@ -333,13 +333,27 @@ Returns a function that calls `fn`. If the returned function has not been called
 exactly `expected` number of times when the test is complete, then the test will
 fail.
 
+If `fn` is not provided, `common.noop` will be used.
+
 ### nodeProcessAborted(exitCode, signal)
 * `exitCode` [<Number>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Number_type)
 * `signal` [<String>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#String_type)
 * return [<Boolean>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type)
 
 Returns `true` if the exit code `exitCode` and/or signal name `signal` represent the exit code and/or signal name of a node process that aborted, `false` otherwise.
 
+### noop
+
+A non-op `Function` that can be used for a variety of scenarios.
+
+For instance,
+
+```js
+const common = require('../common');
+
+someAsyncAPI('foo', common.mustCall(common.noop));
+```
+
 ### opensslCli
 * return [<Boolean>](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Data_structures#Boolean_type)
 

test/addons/async-hello-world/test.js

@@ -6,5 +6,5 @@ const binding = require(`./build/${common.buildType}/binding`);
 binding(5, common.mustCall(function(err, val) {
   assert.strictEqual(err, null);
   assert.strictEqual(val, 10);
-  process.nextTick(common.mustCall(function() {}));
+  process.nextTick(common.mustCall());
 }));

test/addons/heap-profiler/test.js

@@ -5,7 +5,7 @@ const common = require('../../common');
 const binding = require(`./build/${common.buildType}/binding`);
 
 // Create an AsyncWrap object.
-const timer = setTimeout(function() {}, 1);
+const timer = setTimeout(common.noop, 1);
 timer.unref();
 
 // Stress-test the heap profiler.

test/common.js

@@ -35,6 +35,9 @@ const execSync = require('child_process').execSync;
 const testRoot = process.env.NODE_TEST_DIR ?
                    fs.realpathSync(process.env.NODE_TEST_DIR) : __dirname;
 
+const noop = () => {};
+
+exports.noop = noop;
 exports.fixturesDir = path.join(__dirname, 'fixtures');
 exports.tmpDirName = 'tmp';
 // PORT should match the definition in test/testpy/__init__.py.
@@ -429,6 +432,13 @@ function runCallChecks(exitCode) {
 
 
 exports.mustCall = function(fn, expected) {
+  if (typeof fn === 'number') {
+    expected = fn;
+    fn = noop;
+  } else if (fn === undefined) {
+    fn = noop;
+  }
+
   if (expected === undefined)
     expected = 1;
   else if (typeof expected !== 'number')
@@ -525,9 +535,9 @@ util.inherits(ArrayStream, stream.Stream);
 exports.ArrayStream = ArrayStream;
 ArrayStream.prototype.readable = true;
 ArrayStream.prototype.writable = true;
-ArrayStream.prototype.pause = function() {};
-ArrayStream.prototype.resume = function() {};
-ArrayStream.prototype.write = function() {};
+ArrayStream.prototype.pause = noop;
+ArrayStream.prototype.resume = noop;
+ArrayStream.prototype.write = noop;
 
 // Returns true if the exit code "exitCode" and/or signal name "signal"
 // represent the exit code and/or signal name of a node process that aborted,

test/debugger/test-debugger-client.js

@@ -150,7 +150,7 @@ addTest(function(client, done) {
 
 let connectCount = 0;
 const script = 'setTimeout(function() { console.log("blah"); });' +
-               'setInterval(function() {}, 1000000);';
+               'setInterval(common.noop, 1000000);';
 
 let nodeProcess;
 
@@ -193,7 +193,7 @@ function doTest(cb, done) {
         console.error('>>> connecting...');
         c.connect(debug.port);
         c.on('break', function() {
-          c.reqContinue(function() {});
+          c.reqContinue(common.noop);
         });
         c.on('ready', function() {
           connectCount++;

test/message/unhandled_promise_trace_warnings.js

@@ -1,5 +1,5 @@
 // Flags: --trace-warnings
 'use strict';
-require('../common');
+const common = require('../common');
 const p = Promise.reject(new Error('This was rejected'));
-setImmediate(() => p.catch(() => {}));
+setImmediate(() => p.catch(common.noop));

test/parallel/test-assert.js

@@ -20,7 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const a = require('assert');
 
@@ -505,22 +505,22 @@ a.throws(makeBlock(a.deepEqual, args, []));
 // check messages from assert.throws()
 {
   assert.throws(
-    () => { a.throws(() => {}); },
+    () => { a.throws(common.noop); },
     /^AssertionError: Missing expected exception\.$/
   );
 
   assert.throws(
-    () => { a.throws(() => {}, TypeError); },
+    () => { a.throws(common.noop, TypeError); },
     /^AssertionError: Missing expected exception \(TypeError\)\.$/
   );
 
   assert.throws(
-    () => { a.throws(() => {}, 'fhqwhgads'); },
+    () => { a.throws(common.noop, 'fhqwhgads'); },
     /^AssertionError: Missing expected exception: fhqwhgads$/
   );
 
   assert.throws(
-    () => { a.throws(() => {}, TypeError, 'fhqwhgads'); },
+    () => { a.throws(common.noop, TypeError, 'fhqwhgads'); },
     /^AssertionError: Missing expected exception \(TypeError\): fhqwhgads$/
   );
 }

test/parallel/test-async-wrap-check-providers.js

@@ -39,50 +39,48 @@ function init(id, provider) {
   keyList = keyList.filter((e) => e !== pkeys[provider]);
 }
 
-function noop() { }
-
 async_wrap.setupHooks({ init });
 
 async_wrap.enable();
 
 
-setTimeout(function() { }, 1);
+setTimeout(common.noop, 1);
 
-fs.stat(__filename, noop);
+fs.stat(__filename, common.noop);
 
 if (!common.isAix) {
   // fs-watch currently needs special configuration on AIX and we
   // want to improve under https://github.com/nodejs/node/issues/5085.
   // strip out fs watch related parts for now
-  fs.watchFile(__filename, noop);
+  fs.watchFile(__filename, common.noop);
   fs.unwatchFile(__filename);
   fs.watch(__filename).close();
 }
 
-dns.lookup('localhost', noop);
-dns.lookupService('::', 0, noop);
-dns.resolve('localhost', noop);
+dns.lookup('localhost', common.noop);
+dns.lookupService('::', 0, common.noop);
+dns.resolve('localhost', common.noop);
 
 new StreamWrap(new net.Socket());
 
 new (process.binding('tty_wrap').TTY)();
 
-crypto.randomBytes(1, noop);
+crypto.randomBytes(1, common.noop);
 
 common.refreshTmpDir();
 
 net.createServer(function(c) {
   c.end();
   this.close();
 }).listen(common.PIPE, function() {
-  net.connect(common.PIPE, noop);
+  net.connect(common.PIPE, common.noop);
 });
 
 net.createServer(function(c) {
   c.end();
   this.close(checkTLS);
 }).listen(0, function() {
-  net.connect(this.address().port, noop);
+  net.connect(this.address().port, common.noop);
 });
 
 dgram.createSocket('udp4').bind(0, function() {
@@ -99,7 +97,7 @@ function checkTLS() {
     key: fs.readFileSync(common.fixturesDir + '/keys/ec-key.pem'),
     cert: fs.readFileSync(common.fixturesDir + '/keys/ec-cert.pem')
   };
-  const server = tls.createServer(options, noop)
+  const server = tls.createServer(options, common.noop)
     .listen(0, function() {
       const connectOpts = { rejectUnauthorized: false };
       tls.connect(this.address().port, connectOpts, function() {

test/parallel/test-async-wrap-disabled-propagate-parent.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const net = require('net');
 const async_wrap = process.binding('async_wrap');
@@ -28,8 +28,6 @@ function init(uid, type, parentUid, parentHandle) {
   }
 }
 
-function noop() { }
-
 async_wrap.setupHooks({ init });
 async_wrap.enable();
 
@@ -41,7 +39,7 @@ const server = net.createServer(function(c) {
     this.close();
   });
 }).listen(0, function() {
-  net.connect(this.address().port, noop);
+  net.connect(this.address().port, common.noop);
 });
 
 async_wrap.disable();

test/parallel/test-async-wrap-propagate-parent.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const net = require('net');
 const async_wrap = process.binding('async_wrap');
@@ -28,8 +28,6 @@ function init(uid, type, parentUid, parentHandle) {
   }
 }
 
-function noop() { }
-
 async_wrap.setupHooks({ init });
 async_wrap.enable();
 
@@ -41,7 +39,7 @@ const server = net.createServer(function(c) {
     this.close();
   });
 }).listen(0, function() {
-  net.connect(this.address().port, noop);
+  net.connect(this.address().port, common.noop);
 });
 
 

test/parallel/test-async-wrap-throw-from-callback.js

@@ -43,7 +43,7 @@ if (typeof process.argv[2] === 'string') {
   d.on('error', common.mustNotCall());
   d.run(() => {
     // Using randomBytes because timers are not yet supported.
-    crypto.randomBytes(0, () => { });
+    crypto.randomBytes(0, common.noop);
   });
 
 } else {

test/parallel/test-async-wrap-throw-no-init.js

@@ -1,6 +1,6 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const async_wrap = process.binding('async_wrap');
 
@@ -17,9 +17,9 @@ assert.throws(function() {
 }, /init callback is not assigned to a function/);
 
 // Should not throw
-async_wrap.setupHooks({ init: () => {} });
+async_wrap.setupHooks({ init: common.noop });
 async_wrap.enable();
 
 assert.throws(function() {
-  async_wrap.setupHooks(() => {});
+  async_wrap.setupHooks(common.noop);
 }, /hooks should not be set while also enabled/);

test/parallel/test-async-wrap-uid.js

@@ -1,14 +1,14 @@
 'use strict';
 
-require('../common');
+const common = require('../common');
 const fs = require('fs');
 const assert = require('assert');
 const async_wrap = process.binding('async_wrap');
 
 // Give the event loop time to clear out the final uv_close().
 let si_cntr = 3;
 process.on('beforeExit', () => {
-  if (--si_cntr > 0) setImmediate(() => {});
+  if (--si_cntr > 0) setImmediate(common.noop);
 });
 
 const storage = new Map();

test/parallel/test-buffer-includes.js

@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 
 const Buffer = require('buffer').Buffer;
@@ -278,7 +278,7 @@ for (let lengthIndex = 0; lengthIndex < lengths.length; lengthIndex++) {
 const expectedError =
   /^TypeError: "val" argument must be string, number, Buffer or Uint8Array$/;
 assert.throws(() => {
-  b.includes(() => {});
+  b.includes(common.noop);
 }, expectedError);
 assert.throws(() => {
   b.includes({});

test/parallel/test-child-process-bad-stdio.js

@@ -5,7 +5,7 @@ const assert = require('assert');
 const cp = require('child_process');
 
 if (process.argv[2] === 'child') {
-  setTimeout(() => {}, common.platformTimeout(100));
+  setTimeout(common.noop, common.platformTimeout(100));
   return;
 }
 

test/parallel/test-child-process-disconnect.js

@@ -78,7 +78,7 @@ if (process.argv[2] === 'child') {
   }));
 
   // the process should also self terminate without using signals
-  child.on('exit', common.mustCall(function() {}));
+  child.on('exit', common.mustCall());
 
   // when child is listening
   child.on('message', function(obj) {

test/parallel/test-child-process-fork-ref2.js

@@ -20,7 +20,7 @@
 // USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 'use strict';
-require('../common');
+const common = require('../common');
 const fork = require('child_process').fork;
 
 if (process.argv[2] === 'child') {
@@ -29,7 +29,7 @@ if (process.argv[2] === 'child') {
 
   setTimeout(function() {
     console.log('child -> will this keep it alive?');
-    process.on('message', function() { });
+    process.on('message', common.noop);
   }, 400);
 
 } else {

test/parallel/test-child-process-kill.js

@@ -25,9 +25,9 @@ const assert = require('assert');
 const spawn = require('child_process').spawn;
 const cat = spawn(common.isWindows ? 'cmd' : 'cat');
 
-cat.stdout.on('end', common.mustCall(function() {}));
+cat.stdout.on('end', common.mustCall());
 cat.stderr.on('data', common.mustNotCall());
-cat.stderr.on('end', common.mustCall(function() {}));
+cat.stderr.on('end', common.mustCall());
 
 cat.on('exit', common.mustCall(function(code, signal) {
   assert.strictEqual(code, null);