process: add optional code to warnings + type checking

Add the ability to assign an optional code to process warnings +
add additional type checking to ensure that names and codes can
only be strings.

PR-URL: https://github.com/nodejs/node/pull/10116
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Michal Zasso <targos@protonmail.com>
Reviewed-By: Fedor Indutny <fedor.indutny@gmail.com>

doc/api/process.md

@@ -706,14 +706,15 @@ console.log(process.env.test);
 // => 1
 ```
 
-## process.emitWarning(warning[, name][, ctor])
+## process.emitWarning(warning[, type[, code]][, ctor])
 <!-- YAML
 added: v6.0.0
 -->
 
 * `warning` {String | Error} The warning to emit.
-* `name` {String} When `warning` is a String, `name` is the name to use
-  for the warning. Default: `Warning`.
+* `type` {String} When `warning` is a String, `type` is the name to use
+  for the *type* of warning being emitted. Default: `Warning`.
+* `code` {String} A unique identifier for the warning instance being emitted.
 * `ctor` {Function} When `warning` is a String, `ctor` is an optional
   function used to limit the generated stack trace. Default
   `process.emitWarning`
@@ -729,11 +730,16 @@ process.emitWarning('Something happened!');
 ```
 
 ```js
-// Emit a warning using a string and a name...
+// Emit a warning using a string and a type...
 process.emitWarning('Something Happened!', 'CustomWarning');
 // Emits: (node:56338) CustomWarning: Something Happened!
 ```
 
+```js
+process.emitWarning('Something happened!', 'CustomWarning', 'WARN001');
+// Emits: (node:56338) CustomWarning [WARN001]: Something Happened!
+```
+
 In each of the previous examples, an `Error` object is generated internally by
 `process.emitWarning()` and passed through to the
 [`process.on('warning')`][process_warning] event.
@@ -742,21 +748,24 @@ In each of the previous examples, an `Error` object is generated internally by
 process.on('warning', (warning) => {
   console.warn(warning.name);
   console.warn(warning.message);
+  console.warn(warning.code);
   console.warn(warning.stack);
 });
 ```
 
 If `warning` is passed as an `Error` object, it will be passed through to the
-`process.on('warning')` event handler unmodified (and the optional `name`
-and `ctor` arguments will be ignored):
+`process.on('warning')` event handler unmodified (and the optional `type`,
+`code` and `ctor` arguments will be ignored):
 
 ```js
 // Emit a warning using an Error object...
 const myWarning = new Error('Warning! Something happened!');
+// Use the Error name property to specify the type name
 myWarning.name = 'CustomWarning';
+myWarning.code = 'WARN001';
 
 process.emitWarning(myWarning);
-// Emits: (node:56338) CustomWarning: Warning! Something Happened!
+// Emits: (node:56338) CustomWarning [WARN001]: Warning! Something Happened!
 ```
 
 A `TypeError` is thrown if `warning` is anything other than a string or `Error`
@@ -765,7 +774,7 @@ object.
 Note that while process warnings use `Error` objects, the process warning
 mechanism is **not** a replacement for normal error handling mechanisms.
 
-The following additional handling is implemented if the warning `name` is
+The following additional handling is implemented if the warning `type` is
 `DeprecationWarning`:
 
 * If the `--throw-deprecation` command-line flag is used, the deprecation

lib/internal/process/warning.js

@@ -13,26 +13,45 @@ function setupProcessWarnings() {
       const trace = process.traceProcessWarnings ||
                     (isDeprecation && process.traceDeprecation);
       if (trace && warning.stack) {
-        console.error(`${prefix}${warning.stack}`);
+        if (warning.code) {
+          console.error(`${prefix}[${warning.code}] ${warning.stack}`);
+        } else {
+          console.error(`${prefix}${warning.stack}`);
+        }
       } else {
-        var toString = warning.toString;
-        if (typeof toString !== 'function')
-          toString = Error.prototype.toString;
-        console.error(`${prefix}${toString.apply(warning)}`);
+        const toString =
+          typeof warning.toString === 'function' ?
+            warning.toString : Error.prototype.toString;
+        if (warning.code) {
+          console.error(
+              `${prefix}[${warning.code}] ${toString.apply(warning)}`);
+        } else {
+          console.error(`${prefix}${toString.apply(warning)}`);
+        }
       }
     });
   }
 
   // process.emitWarning(error)
-  // process.emitWarning(str[, name][, ctor])
-  process.emitWarning = function(warning, name, ctor) {
-    if (typeof name === 'function') {
-      ctor = name;
-      name = 'Warning';
+  // process.emitWarning(str[, type[, code]][, ctor])
+  process.emitWarning = function(warning, type, code, ctor) {
+    if (typeof type === 'function') {
+      ctor = type;
+      code = undefined;
+      type = 'Warning';
     }
+    if (typeof code === 'function') {
+      ctor = code;
+      code = undefined;
+    }
+    if (code !== undefined && typeof code !== 'string')
+      throw new TypeError('\'code\' must be a String');
+    if (type !== undefined && typeof type !== 'string')
+      throw new TypeError('\'type\' must be a String');
     if (warning === undefined || typeof warning === 'string') {
       warning = new Error(warning);
-      warning.name = name || 'Warning';
+      warning.name = String(type || 'Warning');
+      if (code !== undefined) warning.code = code;
       Error.captureStackTrace(warning, ctor || process.emitWarning);
     }
     if (!(warning instanceof Error)) {

test/parallel/test-process-emitwarning.js

@@ -9,18 +9,21 @@ const util = require('util');
 process.on('warning', common.mustCall((warning) => {
   assert(warning);
   assert(/^(Warning|CustomWarning)/.test(warning.name));
-  assert(warning.message, 'A Warning');
-}, 7));
+  assert.strictEqual(warning.message, 'A Warning');
+  if (warning.code) assert.strictEqual(warning.code, 'CODE001');
+}, 8));
 
 process.emitWarning('A Warning');
 process.emitWarning('A Warning', 'CustomWarning');
 process.emitWarning('A Warning', CustomWarning);
 process.emitWarning('A Warning', 'CustomWarning', CustomWarning);
+process.emitWarning('A Warning', 'CustomWarning', 'CODE001');
 
 function CustomWarning() {
   Error.call(this);
   this.name = 'CustomWarning';
   this.message = 'A Warning';
+  this.code = 'CODE001';
   Error.captureStackTrace(this, CustomWarning);
 }
 util.inherits(CustomWarning, Error);
@@ -36,6 +39,16 @@ warningThrowToString.toString = function() {
 };
 process.emitWarning(warningThrowToString);
 
-// TypeError is thrown on invalid output
+// TypeError is thrown on invalid input
 assert.throws(() => process.emitWarning(1), TypeError);
 assert.throws(() => process.emitWarning({}), TypeError);
+assert.throws(() => process.emitWarning(true), TypeError);
+assert.throws(() => process.emitWarning([]), TypeError);
+assert.throws(() => process.emitWarning('', {}), TypeError);
+assert.throws(() => process.emitWarning('', '', {}), TypeError);
+assert.throws(() => process.emitWarning('', 1), TypeError);
+assert.throws(() => process.emitWarning('', '', 1), TypeError);
+assert.throws(() => process.emitWarning('', true), TypeError);
+assert.throws(() => process.emitWarning('', '', true), TypeError);
+assert.throws(() => process.emitWarning('', []), TypeError);
+assert.throws(() => process.emitWarning('', '', []), TypeError);