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util: inspect all prototypes
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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.

PR-URL: #24974
Fixes: #24917
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Anto Aravinth <[email protected]>
Reviewed-By: James M Snell <[email protected]>
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BridgeAR authored and BethGriggs committed Dec 18, 2018
1 parent a9f239f commit 5931747
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Showing 2 changed files with 25 additions and 9 deletions.
13 changes: 7 additions & 6 deletions lib/internal/util/inspect.js
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
Original file line number Diff line number Diff line change
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

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