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util: fix inspection of module namespaces #20962

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util: fix inspection of module namespaces #20962

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util: fix inspection of module namespaces
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@devsnek
devsnek committed May 29, 2018
commit a9a064347f5a99e969401d9918da48ff7d16ab98
20 changes: 18 additions & 2 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -478,7 +478,23 @@ function formatValue(ctx, value, recurseTimes) {
if (ctx.showHidden) {
keys = Object.getOwnPropertyNames(value);
} else {
keys = Object.keys(value);
// This might throw if `value` is a Module Namespace Object from an
// unevaluated module, but we don't want to perform the actual type
// check because it's expensive.

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// TODO(devsnek): track https://github.com/tc39/ecma262/issues/1209
// and modify this logic as needed.
try {
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@jdalton jdalton May 29, 2018 •
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  • Object.keys and Object.getOwnPropertyNames references should be cherry-picked above.
  • The instanceof ReferenceError check will fail from errors of a different realm (context).

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for the first point, we purposely leave those as-is because some polyfills for things use them to mess with util.

for the second point, i guess types.isNativeError(err) && err.name === 'ReferenceError' would work?

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@jdalton jdalton May 29, 2018 •
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for the first point, we purposely leave those as-is because some polyfills for things use them to mess with util.

Ah cool! Do you have any examples at hand?

for the second point, i guess types.isNativeError(err) && err.name === 'ReferenceError' would work?

Yep.

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I don't know what package does it, but it was brought up during discussions about hardening core against tampering with builtin prototypes.

keys = Object.keys(value);
} catch (err) {
if (types.isNativeError(err) &&
err.name === 'ReferenceError' &&
types.isModuleNamespaceObject(value)) {
keys = Object.getOwnPropertyNames(value);
} else {
throw err;
}
}

if (symbols.length !== 0)
symbols = symbols.filter((key) => propertyIsEnumerable.call(value, key));
}
Expand Down Expand Up @@ -772,7 +788,7 @@ function formatNamespaceObject(ctx, value, recurseTimes, keys) {
try {
output[i] = formatProperty(ctx, value, recurseTimes, keys[i], 0);
} catch (err) {
if (!(err instanceof ReferenceError)) {
if (!(types.isNativeError(err) && err.name === 'ReferenceError')) {
throw err;
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@jdalton jdalton May 29, 2018 •
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Could the error checks be simplified all up? If namespace objects can only error by throwing a reference error then we can assume that the error accessing it is because of the reference error and remove the error checks and rethrow code above. We could also simplify the initial check by doing:

try {
  keys = Object.keys(value);
} catch (err) {
  if (types.isModuleNamespaceObject(value)) {
    keys = Object.getOwnPropertyNames(value);
  } else {
    throw err;
  }
}

Here erroring should be rare and when it does error it is likely a namespace object so the check up-front on error should be fine.

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i think its best to explicitly check if its a reference error, do you feel strongly about this?

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I dig it if code could be simpler, and still correct, that it be simpler is all.

}
// Use the existing functionality. This makes sure the indentation and
Expand Down