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util: fix constructor/instanceof checks
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These new checks are similar to the one introduced in 089d688,
but for other types of objects. Specifically, if an object was
created in a different context, the constructor object will not be
the same as the constructor object in the current context, so we
have to compare constructor names instead.

PR-URL: #3385
Reviewed-By: Evan Lucas <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>
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mscdex committed Dec 1, 2015
1 parent 2fb34b6 commit 82b8355
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Showing 2 changed files with 22 additions and 8 deletions.
20 changes: 12 additions & 8 deletions lib/util.js
Original file line number Diff line number Diff line change
Expand Up @@ -198,6 +198,7 @@ function ensureDebugIsInitialized() {

function inspectPromise(p) {
ensureDebugIsInitialized();
// Only create a mirror if the object is a Promise.
if (!binding.isPromise(p))
return null;
const mirror = Debug.MakeMirror(p, true);
Expand Down Expand Up @@ -299,16 +300,19 @@ function formatValue(ctx, value, recurseTimes) {
var base = '', empty = false, braces;
var formatter = formatObject;

// We can't compare constructors for various objects using a comparison like
// `constructor === Array` because the object could have come from a different
// context and thus the constructor won't match. Instead we check the
// constructor names (including those up the prototype chain where needed) to
// determine object types.
if (Array.isArray(value)) {
// We can't use `constructor === Array` because this could
// have come from a Debug context.
// Otherwise, an Array will print "Array [...]".
// Unset the constructor to prevent "Array [...]" for ordinary arrays.
if (constructor && constructor.name === 'Array')
constructor = null;
braces = ['[', ']'];
empty = value.length === 0;
formatter = formatArray;
} else if (value instanceof Set) {
} else if (objectToString(value) === '[object Set]') {
braces = ['{', '}'];
// With `showHidden`, `length` will display as a hidden property for
// arrays. For consistency's sake, do the same for `size`, even though this
Expand All @@ -317,7 +321,7 @@ function formatValue(ctx, value, recurseTimes) {
keys.unshift('size');
empty = value.size === 0;
formatter = formatSet;
} else if (value instanceof Map) {
} else if (objectToString(value) === '[object Map]') {
braces = ['{', '}'];
// Ditto.
if (ctx.showHidden)
Expand Down Expand Up @@ -347,8 +351,7 @@ function formatValue(ctx, value, recurseTimes) {
'buffer');
}
} else {
// Only create a mirror if the object superficially looks like a Promise.
var promiseInternals = value instanceof Promise && inspectPromise(value);
var promiseInternals = inspectPromise(value);
if (promiseInternals) {
braces = ['{', '}'];
formatter = formatPromise;
Expand All @@ -364,7 +367,8 @@ function formatValue(ctx, value, recurseTimes) {
empty = false;
formatter = formatCollectionIterator;
} else {
if (constructor === Object)
// Unset the constructor to prevent "Object {...}" for ordinary objects.
if (constructor && constructor.name === 'Object')
constructor = null;
braces = ['{', '}'];
empty = true; // No other data than keys.
Expand Down
10 changes: 10 additions & 0 deletions test/parallel/test-util-inspect.js
Original file line number Diff line number Diff line change
Expand Up @@ -194,6 +194,16 @@ for (const o of vals) {

assert.strictEqual(util.inspect(valsOutput), '[ [ 1, 2 ] ]');

// test for other constructors in different context
var obj = require('vm').runInNewContext('(function(){return {}})()', {});
assert.strictEqual(util.inspect(obj), '{}');
obj = require('vm').runInNewContext('var m=new Map();m.set(1,2);m', {});
assert.strictEqual(util.inspect(obj), 'Map { 1 => 2 }');
obj = require('vm').runInNewContext('var s=new Set();s.add(1);s.add(2);s', {});
assert.strictEqual(util.inspect(obj), 'Set { 1, 2 }');
obj = require('vm').runInNewContext('fn=function(){};new Promise(fn,fn)', {});
assert.strictEqual(util.inspect(obj), 'Promise { <pending> }');

// test for property descriptors
var getter = Object.create(null, {
a: {
Expand Down

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