8000 fix: harden getRawTag against non-configurable and accessor Symbol.toStringTag by scrrlt · Pull Request #6078 · lodash/lodash · GitHub
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fix: harden getRawTag against non-configurable and accessor Symbol.toStringTag #6078

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fix: harden getRawTag against non-configurable and accessor Symbol.toStringTag #6078

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@scrrlt scrrlt commented Jan 5, 2026 •
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summary

  • improves the stability of getRawTag by using Object.getOwnPropertyDescriptor to safely mask and unmask the Symbol.toStringTag property. It prevents TypeError in strict mode and ensures that getters/setters on the prototype chain are not destroyed during type detection.
  • current implementation assumes Symbol.toStringTag is always a simple, writable data property. causing two critical failures:
  • attempting to assign undefined to a non-configurable or read-only toStringTag throws a TypeError in strict mode.
  • If toStringTag is a getter, the current implementation overwrites it with undefined, permanently destroying the getter mechanism on the object instance.

fix

  • verifies property descriptors before assignment to ensure the property is configurable.
  • preserves the original property state (including getters/setters) using Object.defineProperty rather than simple assignment.
  • prevents temporary tag patching from leaking between lookups by ensuring cleanup occurs even if errors are thrown.
  • includes a fallback for environments without getOwnPropertyDescriptor, ensuring Object.prototype.toString is used when the tag cannot be safely modified.

test coverage
added a new test suite test/getRawTag.spec.js covering the following edge cases:

  • DataView instances (regression check).
  • non-configurable Symbol.toStringTag (prevents crash).
  • prototype setters that throw errors (hostile environment check).
  • restoration of accessor-based toStringTag after execution.

@scrrlt scrrlt changed the title fix: harden getRawTag fallback when Symbol.toStringTag is masked fix: harden getRawTag against non-configurable and accessor Symbol.toStringTag Jan 5, 2026
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