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util: inspect all prototypes #24974

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util: inspect all prototypes #24974

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util: inspect all prototypes 
It is currently difficult to distinguish multiple objects from each
other because the prototype is not properly inspected. From now on
all prototypes will be inspected, even if we do not fully know how
they will look like / what their shape really is.

Fixes: #24917
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@BridgeAR
BridgeAR committed Dec 11, 2018
commit 5a2cc3af8a7848dc0eed81445af79b1eb1409b81
13 changes: 7 additions & 6 deletions lib/internal/util/inspect.js
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Original file line number Diff line number Diff line change
Expand Up @@ -322,7 +322,7 @@ function getEmptyFormatArray() {
return [];
}

function getConstructorName(obj) {
function getConstructorName(obj, ctx) {
let firstProto;
while (obj) {
const descriptor = Object.getOwnPropertyDescriptor(obj, 'constructor');
Expand All @@ -341,10 +341,11 @@ function getConstructorName(obj) {
if (firstProto === null) {
return null;
}
// TODO(BridgeAR): Improve prototype inspection.
// We could use inspect on the prototype itself to improve the output.

return '';
return `<${inspect(firstProto, {
...ctx,
customInspect: false
})}>`;
}

function getPrefix(constructor, tag, fallback) {
Expand Down Expand Up @@ -503,7 +504,7 @@ function formatValue(ctx, value, recurseTimes) {
}

if (ctx.stop !== undefined) {
const name = getConstructorName(value) || value[Symbol.toStringTag];
const name = getConstructorName(value, ctx) || value[Symbol.toStringTag];
return ctx.stylize(`[${name || 'Object'}]`, 'special');
}

Expand Down Expand Up @@ -547,7 +548,7 @@ function formatValue(ctx, value, recurseTimes) {
function formatRaw(ctx, value, recurseTimes) {
let keys;

const constructor = getConstructorName(value);
const constructor = getConstructorName(value, ctx);
let tag = value[Symbol.toStringTag];
if (typeof tag !== 'string')
tag = '';
Expand Down
21 changes: 18 additions & 3 deletions test/parallel/test-util-inspect.js
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Expand Up @@ -1738,19 +1738,34 @@ assert.strictEqual(
);
}

// Manipulate the prototype to one that we can not handle.
// Manipulate the prototype in weird ways.
{
let obj = { a: true };
let value = (function() { return function() {}; })();
Object.setPrototypeOf(value, null);
Object.setPrototypeOf(obj, value);
assert.strictEqual(util.inspect(obj), '{ a: true }');
assert.strictEqual(util.inspect(obj), '<[Function]> { a: true }');
assert.strictEqual(
util.inspect(obj, { colors: true }),
'<\u001b[36m[Function]\u001b[39m> { a: \u001b[33mtrue\u001b[39m }'
);

obj = { a: true };
value = [];
Object.setPrototypeOf(value, null);
Object.setPrototypeOf(obj, value);
assert.strictEqual(util.inspect(obj), '{ a: true }');
assert.strictEqual(
util.inspect(obj),
'<[Array: null prototype] []> { a: true }'
);

function StorageObject() {}
StorageObject.prototype = Object.create(null);
assert.strictEqual(
util.inspect(new StorageObject()),
'<[Object: null prototype] {}> {}'
);

}

// Check that the fallback always works.
Expand Down