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Symbol key props visible in inspection by default #9726

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Symbol key props visible in inspection by default #9726

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903f353
Symbol key props visible in inspection by default
mightyiam Nov 21, 2016
192d79a
test/parallel/test-util-inspect: const UTC -> const UIC
mightyiam Nov 22, 2016
3ace6a9
Excl. non-enumerable property symbols from inspection by default
mightyiam Nov 24, 2016
8e73c95
lib/util: use const for symbolKeys & enumSymbolKeys
mightyiam Nov 24, 2016
3cbd847
lib/util: fix indentation of enumSymbolKeys's filter call
mightyiam Nov 24, 2016
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5 changes: 3 additions & 2 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -371,10 +371,11 @@ function formatValue(ctx, value, recurseTimes) {
// Look up the keys of the object.
var keys = Object.keys(value);
var visibleKeys = arrayToHash(keys);
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I don't fully understand what goes on with keys vs. visibleKeys, yet, this seems to work.

var symbolKeys = Object.getOwnPropertySymbols(value);
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I haven’t run this but right now this looks like this will include even *non-*enumerable Symbol properties?

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Yup. That is how Object.getOwnPropertySymbols works. It is like the conversation between it and Object.getOwnPropertyNames is:

  • Object.getOwnPropertyNames: Hey, Symbol. You may join. But don't expect me to list you, even if you're enumerable...
  • Symbol: 😐
  • Object.getOwnPropertySymbols: Gee, did you see that guy? Tell you what, Symbol. I'll list all of you, regardless!
  • Symbol: 😟
  • Object.getOwnPropertyNames: 😦
  • Object.getOwnPropertySymbols: 😊
  • Symbol: 😕

I wouldn't mind changing it to exclude non-enumerable symbol-keyed props. Should I?

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Well… it seems a bit weird to list only enumerable string properties but all Symbol properties by default?

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I just don't know the reasons for not listing non-enumerable properties. For the sake of explaining my experience with the matter, I'll testify that I:

  1. never made a property non-enumerable before examining this issue
  2. never had to examine the non-enumerable properties of an object. At least not that I know of.

So, it may help that one with experience with the topic of enumerability and non-enumerability will share his thoughts. Also, the thoughts of one who knows the intention of symbols in this regard and why this is the behavior of Object.getOwnPropertySymbols.

keys = keys.concat(symbolKeys);

if (ctx.showHidden) {
keys = Object.getOwnPropertyNames(value);
keys = keys.concat(Object.getOwnPropertySymbols(value));
keys = Object.getOwnPropertyNames(value).concat(symbolKeys);
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This is the same result. The change is to not get the symbols twice.

}

// This could be a boxed primitive (new String(), etc.), check valueOf()
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10 changes: 5 additions & 5 deletions test/parallel/test-util-inspect.js
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Expand Up @@ -588,8 +588,9 @@ assert.doesNotThrow(function() {
'{ a: 123, inspect: [Function: inspect] }');

const subject = { a: 123, [util.inspect.custom]() { return this; } };
const UTC = 'util.inspect.custom';
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This trick is solely for line length.

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It seems fine because this is in a small block.

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IMHO 'UTC' isn't a particularly good name. To me, it makes me think of Coordinated Universal Time, but the variable value does not hold anything date/time-related.

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Oops. Just a typo. I meant UIC for util.inspect.custom But, from Wikipedia:

UIC may refer to:

In education:

Underwood International College, a department of Yonsei University
United International College, a liberal arts college in China
University of Illinois at Chicago, a public four-year university in Chicago, Illinois
In government:

Uganda Insurance Commission, a government agency
Unit Identification Code, an alphanumeric code used by the United States Department of Defense
In organisations:

International Union of Railways (Union Internationale des Chemins de fer), an international rail transport industry body
UEFA Intertoto Cup, an association football tournament for member clubs of UEFA
Union of Islamic Courts, an armed group in Somalia, now called the "Supreme Islamic Courts Council"
United Industrial Corporation Ltd, a Singapore real estate holding company owned by JG Summit Holdings
In computing:

Uranium Information Centre, a defunct website sponsored by uranium mining companies
User identification code, the user number of the Files-11 file system in the RSX-11 operating system
In other uses:

UIC (band), a punk rock band from Canada
UIC Flames, the intercollegiate athletic program of the University of Illinois at Chicago

What is a good name?

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@mightyiam It might be best not to give this a name at all but instead spread the string below across multiple lines?

assert.strictEqual(util.inspect(subject),
'{ a: 123 }');
`{ a: 123,\n [Symbol(${UTC})]: [Function: [${UTC}]] }`);
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This is a fix for a seemingly unrelated test that is affected.

}

// util.inspect with "colors" option should produce as many lines as without it
Expand Down Expand Up @@ -659,7 +660,7 @@ if (typeof Symbol !== 'undefined') {

subject[Symbol('symbol')] = 42;

assert.strictEqual(util.inspect(subject), '{}');
assert.strictEqual(util.inspect(subject), '{ [Symbol(symbol)]: 42 }');
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This demonstrates the change.

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@mightyiam mightyiam Nov 21, 2016 •
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Just the way I like it 😉

assert.strictEqual(
util.inspect(subject, options),
'{ [Symbol(symbol)]: 42 }'
Expand All @@ -668,9 +669,8 @@ if (typeof Symbol !== 'undefined') {
subject = [1, 2, 3];
subject[Symbol('symbol')] = 42;

assert.strictEqual(util.inspect(subject), '[ 1, 2, 3 ]');
assert.strictEqual(util.inspect(subject, options),
'[ 1, 2, 3, [length]: 3, [Symbol(symbol)]: 42 ]');
assert.strictEqual(util.inspect(subject),
'[ 1, 2, 3, [Symbol(symbol)]: 42 ]');
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@mightyiam mightyiam Nov 21, 2016 •
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This assertion is removed because we already have an assertion above that symbol key properties are visible with showHidden.

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So in essence, this assertion is not instead of the one in 672, but instead of the one in 671. I guess it shows that symbol key properties can coexist peacefully with other properties in inspection. Or something about the order of properties? In any case, I'm guessing that the essence is preserved.

}

// test Set
Expand Down