util: support classes in util.deprecate()

Classes cannot be instantiated without new, but util.deprecate() uses Function.prototype.apply(). This commit uses new.target to detect constructor calls, allowing classes to be deprecated. PR-URL: #7690 Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: Michaël Zasso <[email protected]> Reviewed-By: James M Snell <[email protected]>

Author: vdeturckheim

doc/api/util.md

@@ -46,7 +46,7 @@ environment variable. For example: `NODE_DEBUG=fs,net,tls`.
 
 ## util.deprecate(function, string)
 
-The `util.deprecate()` method wraps the given `function` in such a way that
+The `util.deprecate()` method wraps the given `function`or class in such a way that
 it is marked as deprecated.
 
 ```js

lib/internal/util.js

@@ -57,9 +57,18 @@ exports._deprecate = function(fn, msg){
 varwarned=false;
 functiondeprecated(){
 warned=exports.printDeprecationMessage(msg,warned,deprecated);
+if(new.target){
+returnReflect.construct(fn,arguments,new.target);
+}
 returnfn.apply(this,arguments);
 }
 
+// The wrapper will keep the same prototype as fn to maintain prototype chain
+Object.setPrototypeOf(deprecated,fn);
+if(fn.prototype){
+Object.setPrototypeOf(deprecated.prototype,fn.prototype);
+}
+
 returndeprecated;
 };
 

test/fixtures/deprecated-userland-class.js

@@ -0,0 +1,12 @@
+constutil=require('util');
+constassert=require('assert');
+
+classdeprecatedClass{
+}
+
+constdeprecated=util.deprecate(deprecatedClass,'deprecatedClass is deprecated.');
+
+constinstance=newdeprecated();
+
+assert(instanceinstanceofdeprecated);
+assert(instanceinstanceofdeprecatedClass);

test/fixtures/deprecated-userland-subclass.js

@@ -0,0 +1,19 @@
+constutil=require('util');
+constassert=require('assert');
+
+classdeprecatedClass{
+}
+
+constdeprecated=util.deprecate(deprecatedClass,'deprecatedClass is deprecated.');
+
+classsubclassextendsdeprecated{
+constructor(){
+super();
+}
+}
+
+constinstance=newsubclass();
+
+assert(instanceinstanceofsubclass);
+assert(instanceinstanceofdeprecated);
+assert(instanceinstanceofdeprecatedClass);

test/sequential/test-deprecation-flags.js

@@ -5,8 +5,14 @@ const execFile = require('child_process').execFile;
 constdepmod=require.resolve(common.fixturesDir+'/deprecated.js');
 constnode=process.execPath;
 
-constdepUserland=
-require.resolve(common.fixturesDir+'/deprecated-userland-function.js');
+constdepUserlandFunction=
+require.resolve(common.fixturesDir+'/deprecated-userland-function.js');
+
+constdepUserlandClass=
+require.resolve(common.fixturesDir+'/deprecated-userland-class.js');
+
+constdepUserlandSubClass=
+require.resolve(common.fixturesDir+'/deprecated-userland-subclass.js');
 
 constnormal=[depmod];
 constnoDep=['--no-deprecation',depmod];
@@ -39,10 +45,22 @@ execFile(node, traceDep, function(er, stdout, stderr){
 console.log('trace ok');
 });
 
-execFile(node,[depUserland],function(er,stdout,stderr){
+execFile(node,[depUserlandFunction],function(er,stdout,stderr){
 console.error('normal: testing deprecated userland function');
 assert.equal(er,null);
 assert.equal(stdout,'');
 assert(/deprecatedFunctionisdeprecated/.test(stderr));
 console.error('normal: ok');
 });
+
+execFile(node,[depUserlandClass],function(er,stdout,stderr){
+assert.strictEqual(er,null);
+assert.strictEqual(stdout,'');
+assert(/deprecatedClassisdeprecated/.test(stderr));
+});
+
+execFile(node,[depUserlandSubClass],function(er,stdout,stderr){
+assert.strictEqual(er,null);
+assert.strictEqual(stdout,'');
+assert(/deprecatedClassisdeprecated/.test(stderr));
+});