fix: polyfill Map.prototype.getOrInsertComputed to stop PDF.js render crash

[mvanhorn]

Description

Fetched pdfjs-dist@5.5.207 (the version currently resolved by package-lock.json under the ^5.4.624 caret range) from unpkg and confirmed the crash site directly: PDFPageProxy.render() unconditionally calls this._transport.getOptionalContentConfig(renderingIntent), which calls #cacheSimpleMethod("GetOptionalContentConfig"), which calls this.#methodPromises.getOrInsertComputed(name, () => ...) (build/pdf.mjs line ~15510) - an exact match for the minified stack trace in the issue (this.#e.getOrInsertComputed(t,()=>this.messageHandler.sendWithPromise(t,e))). render() also calls this._intentStates.getOrInsertComputed(cacheKey, makeObj) on the same code path. Map.prototype.getOrInsertComputed is a very recent TC39 "Upsert" built-in that pdfjs-dist now relies on unconditionally, without feature-detection or a bundled polyfill - so it crashes in any browser/engine that lacks native support, which explains why it fails identically across Safari 18.6 and the reporter's Chrome build, and also explains the second, independently-reported crash in pdf-multi-tool (any tool calling pdfJsPage.render() is affected, not just OCR).

/ocr-pdf.html crashes on every PDF with TypeError: this.#e.getOrInsertComputed is not a function, thrown from PDF.js's render() -> getOptionalContentConfig() path (main-*.js chunk). Reproduced on both Safari 18.6 and Chrome latest, on a self-hosted Docker deployment (ghcr.io/alam00000/bentopdf-simple:latest). The reporter speculated a worker/main-thread PDF.js version mismatch, but src/js/main.ts sets GlobalWorkerOptions.workerSrc via Vite's new URL('pdfjs-dist/build/pdf.worker.min.mjs', import.meta.url), which always resolves to the same installed pdfjs-dist package as the main thread - so worker/main are in lockstep, ruling that theory out. A second reporter (BlackWolfWoof, 2026-07-12) hit an apparently related crash in the unrelated pdf-multi-tool, which also calls `pdfJsPage.render({ canvasContext, ...

Fixes #662

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

🧪 How Has This Been Tested?

Native support present: if Map.prototype.getOrInsertComputed already exists (feature-detected via Map.prototype.hasOwnProperty or typeof check), the polyfill module does not overwrite it - assert the original function reference is unchanged after import.
Polyfill installs when missing: delete/stub Map.prototype.getOrInsertComputed before import (or test the standalone install function against a plain object shaped like a Map), then call it on a Map instance and assert it exists as a function afterward.
Existing key: map.getOrInsertComputed(key, cb) on a Map that already has key returns the existing value and never invokes cb.
Missing key: map.getOrInsertComputed(key, cb) on a Map without key invokes cb(key) exactly once, stores the result under key, and returns it.
Regression guard: a lightweight smoke test (or comment referencing the OCR/PDF.js path) documenting that this polyfill is what unblocks pdfjsPage.render() in getOptionalContentConfig, so a future removal of the import doesn't silently reintroduce the crash.

Checklist:

• I have signed the Contributor License Agreement (CLA) or my organization has signed the Corporate CLA
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Summary by CodeRabbit

• Compatibility

  • Added support for modern Map convenience methods in environments where they are unavailable.
  • Preserves existing native implementations when supported.

• Bug Fixes

  • Ensures map values can be retrieved or created consistently during application startup.
  • Added validation for computed value callbacks.

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 81e01832-5a25-447b-9d29-290c1ac62484

📥 Commits

Reviewing files that changed from the base of the PR and between 21c924a and 115bc70.

📒 Files selected for processing (3)

• src/js/main.ts
• src/js/utils/map-upsert-polyfill.ts
• src/tests/map-upsert-polyfill.test.ts

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📝 Walkthrough

Walkthrough

The change adds conditional Map.prototype.getOrInsert and getOrInsertComputed polyfills, imports them before pdfjs-dist during startup, and adds Vitest coverage for native preservation, installation, descriptors, behavior, and import ordering.

Changes

Map upsert polyfill

Layer / File(s)	Summary
Map upsert method implementation src/js/utils/map-upsert-polyfill.ts	Defines missing getOrInsert and getOrInsertComputed methods with cached-value, insertion, callback validation, and computed-value behavior.
Startup wiring and behavioral validation src/js/main.ts, src/tests/map-upsert-polyfill.test.ts	Loads the polyfill before pdfjs-dist and tests native preservation, descriptors, upsert semantics, and import ordering.

Estimated code review effort: 2 (Simple) | ~10 minutes

Sequence Diagram(s)

sequenceDiagram
  participant Application
  participant map_upsert_polyfill
  participant pdfjs_dist
  Application->>map_upsert_polyfill: import at startup
  map_upsert_polyfill->>map_upsert_polyfill: install missing Map methods
  Application->>pdfjs_dist: import after polyfill
  pdfjs_dist-->>Application: initialize rendering dependency

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🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: adding a Map.prototype.getOrInsertComputed polyfill to fix the PDF.js crash.
Description check	✅ Passed	The description includes the fix summary, issue reference, motivation/context, and detailed testing notes, with only minor template fields left unfilled.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[alam00000]

Thank you! But you would need to accept the CLA by typing "I have read the CLA Document and I hereby sign the CLA" in the comments so I can merge it.

[mvanhorn]

I have read the CLA Document and I hereby sign the CLA