test: add common.noop, default for common.mustCall()

Export a new common.noop no-operation function for general use.
Allow using common.mustCall() without a fn argument to simplify
test cases.

Replace various non-op functions throughout tests with common.noop

PR-URL: #12027
Reviewed-By: Jeremiah Senkpiel <[email protected]>
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Gibson Fahnestock <[email protected]>
Reviewed-By: Teddy Katz <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Franziska Hinkelmann <[email protected]>

Author: jasnell

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/common/index.js

@@ -12,6 +12,9 @@ const Timer = process.binding('timer_wrap').Timer;
 const testRoot = process.env.NODE_TEST_DIR ?
   fs.realpathSync(process.env.NODE_TEST_DIR) : path.resolve(__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.
@@ -419,6 +422,13 @@ 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')
@@ -487,9 +497,9 @@ 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

@@ -129,7 +129,7 @@ addTest(function(client, done) {
 
 let connectCount = 0;
 const script = 'setTimeout(function() { console.log("blah"); });' +
-               'setInterval(function() {}, 1000000);';
+               'setInterval(common.noop, 1000000);';
 
 let nodeProcess;
 
@@ -172,7 +172,7 @@ 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/parallel/test-assert.js

@@ -1,5 +1,5 @@
 'use strict';
-require('../common');
+const common = require('../common');
 const assert = require('assert');
 const a = require('assert');
 
@@ -515,6 +515,7 @@ testAssertionMessage(/a/, '/a/');
 testAssertionMessage(/abc/gim, '/abc/gim');
 testAssertionMessage(function f() {}, '[Function: f]');
 testAssertionMessage(function() {}, '[Function]');
+testAssertionMessage(common.noop, '[Function: noop]');
 testAssertionMessage({}, '{}');
 testAssertionMessage(circular, '{ y: 1, x: [Circular] }');
 testAssertionMessage({a: undefined, b: null}, '{ a: undefined, b: null }');

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

@@ -57,7 +57,7 @@ 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-kill.js

@@ -4,9 +4,9 @@ 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);

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

@@ -22,11 +22,11 @@ cat.stdout.on('data', function(chunk) {
   response += chunk;
 });
 
-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(status) {
   assert.strictEqual(0, status);

test/parallel/test-cluster-eaccess.js

@@ -14,10 +14,10 @@ if (cluster.isMaster) {
   const worker = cluster.fork();
 
   // makes sure master is able to fork the worker
-  cluster.on('fork', common.mustCall(function() {}));
+  cluster.on('fork', common.mustCall());
 
   // makes sure the worker is ready
-  worker.on('online', common.mustCall(function() {}));
+  worker.on('online', common.mustCall());
 
   worker.on('message', common.mustCall(function(err) {
     // disconnect first, so that we will not leave zombies

test/parallel/test-cluster-setup-master-emit.js

@@ -22,5 +22,5 @@ function emitAndCatch2(next) {
 }
 
 emitAndCatch(common.mustCall(function() {
-  emitAndCatch2(common.mustCall(function() {}));
+  emitAndCatch2(common.mustCall());
 }));

test/parallel/test-cluster-worker-destroy.js

@@ -17,8 +17,8 @@ if (cluster.isMaster) {
   worker2 = cluster.fork();
 
   [worker1, worker2].forEach(function(worker) {
-    worker.on('disconnect', common.mustCall(function() {}));
-    worker.on('exit', common.mustCall(function() {}));
+    worker.on('disconnect', common.mustCall());
+    worker.on('exit', common.mustCall());
   });
 } else {
   if (cluster.worker.id === 1) {