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Fail verbosely on invalid use of util.inherits #1240

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Fail verbosely on invalid use of util.inherits #1240

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eddea81
Check input to util.inherits
connor4312 Mar 23, 2015
e927288
Prototype is allowed to be null, just not undefined
connor4312 Mar 23, 2015
7131380
Use manual checks
connor4312 Mar 23, 2015
f32b402
Line length
connor4312 Mar 23, 2015
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10 changes: 10 additions & 0 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -616,8 +616,18 @@ exports.log = function() {
* @param {function} ctor Constructor function which needs to inherit the
* prototype.
* @param {function} superCtor Constructor function to inherit prototype from.
* @throws {TypeError} Will error if either constructor is null, or if
* the super constructor lacks a prototype.
*/
exports.inherits = function(ctor, superCtor) {

if (ctor === undefined || ctor === null)
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Do you have any opinions on loose equality here and below, i.e. ctor == null? I think it would behave the same way, but that's your call to use or not

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That in turn triggers a jshint error. Wasn't feeling ballsy enough to add a jshint ignore line in my first PR :P

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Yes == null is exactly the same as === null || === undefined

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io.js uses the closure linter, so a jshint ignore line wouldn't be necessary, unless it also does the same.

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It does. I originally used == null, but that triggered an error.

throw new TypeError('The constructor to `inherits` must not be null.');
if (superCtor === undefined || superCtor === null)
throw new TypeError('The super constructor to `inherits` must not be null.');
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This line is over 80 lines (make jslint), could you somehow fix that?

if (superCtor.prototype === undefined)
throw new TypeError('The super constructor must have a prototype.');

ctor.super_ = superCtor;
ctor.prototype = Object.create(superCtor.prototype, {
constructor: {
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7 changes: 7 additions & 0 deletions test/parallel/test-util.js
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Expand Up @@ -78,3 +78,10 @@ assert.deepEqual(util._extend({a:1}, true), {a:1});
assert.deepEqual(util._extend({a:1}, false), {a:1});
assert.deepEqual(util._extend({a:1}, {b:2}), {a:1, b:2});
assert.deepEqual(util._extend({a:1, b:2}, {b:3}), {a:1, b:3});

// inherits
var ctor = function() {};
assert.throws(function() { util.inherits(ctor, {}) }, TypeError);
assert.throws(function() { util.inherits(ctor, null) }, TypeError);
assert.throws(function() { util.inherits(null, ctor) }, TypeError);
assert.doesNotThrow(function() { util.inherits(ctor, ctor) }, TypeError);