[api-minor] Convert `getFieldObjects` to return data in a Map by Snuffleupagus · Pull Request #21671 · mozilla/pdf.js

Snuffleupagus · 2026-07-31T09:40:54Z

Compared to regular Objects there's a number of advantages to using Maps:

They support proper iteration.
They have a simple way to check for the existence of data.
They have a simple/efficient way to check the number of elements.

If this functionality was added today, I cannot imagine that we'd choose an Object for this data.

In the Firefox PDF Viewer sending Maps to the scripting-implementation should be fine, since it uses the browser Cu.cloneInto functionality; see https://searchfox.org/firefox-main/source/toolkit/components/pdfjs/content/PdfSandbox.sys.mjs
However with QuickJS, used by the GENERIC viewer, all data needs to be stringified and Maps are converted into regular Objects (see also PR #21664). Hence the objects property, in the scripting-implementation, is converted back into a Map using the (renamed) createMap helper function.

Smaller diff with https://github.com/mozilla/pdf.js/pull/21671/changes?w=1

codecov-commenter · 2026-07-31T09:42:13Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.00%. Comparing base (7590ad5) to head (8871631).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21671      +/-   ##
==========================================
- Coverage   90.00%   90.00%   -0.01%     
==========================================
  Files         263      263              
  Lines       66861    66861              
==========================================
- Hits        60177    60176       -1     
- Misses       6684     6685       +1

Flag	Coverage Δ
browsertest	`66.52% <33.33%> (+<0.01%)`	⬆️
fonttest	`9.04% <ø> (ø)`
integrationtest	`69.35% <100.00%> (+<0.01%)`	⬆️
unittest	`57.83% <44.44%> (-0.01%)`	⬇️
unittestcli	`56.56% <44.44%> (-0.02%)`	⬇️

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Snuffleupagus · 2026-07-31T10:25:35Z

/botio browsertest

moz-tools-bot · 2026-07-31T10:25:38Z

From: Bot.io (Windows)

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.193.163.58:8877/5d841a3b74051e1/output.txt

moz-tools-bot · 2026-07-31T10:25:38Z

From: Bot.io (Linux m4)

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.241.84.105:8877/b839e6a4d9f7903/output.txt

moz-tools-bot · 2026-07-31T10:43:38Z

From: Bot.io (Linux m4)

Success

Full output at http://54.241.84.105:8877/b839e6a4d9f7903/output.txt

Total script time: 17.98 mins

Regression tests: Passed

moz-tools-bot · 2026-07-31T10:49:03Z

From: Bot.io (Windows)

Success

Full output at http://54.193.163.58:8877/5d841a3b74051e1/output.txt

Total script time: 23.42 mins

Regression tests: Passed

Compared to regular Objects there's a number of advantages to using Maps: - They support proper iteration. - They have a simple way to check for the existence of data. - They have a simple/efficient way to check the number of elements. If this functionality was added today, I cannot imagine that we'd choose an Object for this data. In the Firefox PDF Viewer sending Maps to the scripting-implementation should be fine, since it uses the browser `Cu.cloneInto` functionality; see https://searchfox.org/firefox-main/source/toolkit/components/pdfjs/content/PdfSandbox.sys.mjs However with QuickJS, used by the GENERIC viewer, all data needs to be stringified and Maps are converted into regular Objects (see also PR 21664). Hence the `objects` property, in the scripting-implementation, is converted back into a Map using the (renamed) `createMap` helper function.

See commit ce4ff55

timvandermeij · 2026-08-02T20:37:28Z

Nice work; thanks!

Snuffleupagus added core form-js labels Jul 31, 2026

Snuffleupagus temporarily deployed to code-coverage July 31, 2026 09:41 — with GitHub Actions Inactive