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util: change sparse arrays inspection format

Missing elements in sparse arrays used to be serialized to empty
placeholders delimited with commas by util.inspect() and in some cases
the result was a syntactically correct representation of a JavaScript
array with shorter length than the original one. This commit implements
@TimothyGu's suggestion to change the way util.inspect() formats sparse
arrays to something similar to how Firefox shows them.

Fixes: #11570
PR-URL: #11576
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
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aqrln authored and addaleax committed Feb 27, 2017
1 parent 6df23fa commit ec2f098156d7abe169aa846ba4bc51a2d9125ba7
Showing with 35 additions and 13 deletions.
  1. +17 −7 lib/util.js
  2. +18 −6 test/parallel/test-util-inspect.js
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@@ -626,16 +626,26 @@ function formatObject(ctx, value, recurseTimes, visibleKeys, keys) {
function formatArray(ctx, value, recurseTimes, visibleKeys, keys) {
var output = [];
const maxLength = Math.min(Math.max(0, ctx.maxArrayLength), value.length);
const remaining = value.length - maxLength;
for (var i = 0; i < maxLength; ++i) {
if (hasOwnProperty(value, String(i))) {
output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
String(i), true));
let visibleLength = 0;
let index = 0;
while (index < value.length && visibleLength < ctx.maxArrayLength) {
let emptyItems = 0;
while (index < value.length && !hasOwnProperty(value, String(index))) {
emptyItems++;
index++;
}
if (emptyItems > 0) {
const ending = emptyItems > 1 ? 's' : '';
const message = `<${emptyItems} empty item${ending}>`;
output.push(ctx.stylize(message, 'undefined'));
} else {
output.push('');
output.push(formatProperty(ctx, value, recurseTimes, visibleKeys,
String(index), true));
index++;
}
visibleLength++;
}
const remaining = value.length - index;
if (remaining > 0) {
output.push(`... ${remaining} more item${remaining > 1 ? 's' : ''}`);
}
@@ -295,12 +295,18 @@ assert.strictEqual(util.inspect(-0), '-0');
const a = ['foo', 'bar', 'baz'];
assert.strictEqual(util.inspect(a), '[ \'foo\', \'bar\', \'baz\' ]');
delete a[1];
assert.strictEqual(util.inspect(a), '[ \'foo\', , \'baz\' ]');
assert.strictEqual(util.inspect(a), '[ \'foo\', <1 empty item>, \'baz\' ]');
assert.strictEqual(
util.inspect(a, true),
'[ \'foo\', , \'baz\', [length]: 3 ]'
'[ \'foo\', <1 empty item>, \'baz\', [length]: 3 ]'
);
assert.strictEqual(util.inspect(new Array(5)), '[ <5 empty items> ]');
a[3] = 'bar';
a[100] = 'qux';
assert.strictEqual(
util.inspect(a, { breakLength: Infinity }),
'[ \'foo\', <1 empty item>, \'baz\', \'bar\', <96 empty items>, \'qux\' ]'
);
assert.strictEqual(util.inspect(new Array(5)), '[ , , , , ]');
// test for Array constructor in different context
{
@@ -835,15 +841,21 @@ checkAlignment(new Map(big_array.map(function(y) { return [y, null]; })));
// Do not backport to v5/v4 unless all of
// https://github.com/nodejs/node/pull/6334 is backported.
{
const x = Array(101);
const x = new Array(101).fill();
assert(/1 more item/.test(util.inspect(x)));
}
{
const x = Array(101);
const x = new Array(101).fill();
assert(!/1 more item/.test(util.inspect(x, {maxArrayLength: 101})));
}
{
const x = new Array(101).fill();
assert(/^\[ ... 101 more items ]$/.test(
util.inspect(x, {maxArrayLength: 0})));
}
{
const x = Array(101);
assert(/^\[ ... 101 more items ]$/.test(
@@ -901,7 +913,7 @@ checkAlignment(new Map(big_array.map(function(y) { return [y, null]; })));
// util.inspect.defaultOptions tests
{
const arr = Array(101);
const arr = new Array(101).fill();
const obj = {a: {a: {a: {a: 1}}}};
const oldOptions = Object.assign({}, util.inspect.defaultOptions);

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