feat(html): implement asset URL rewriting for <iframe srcdoc> in HTML by bjohansebas · Pull Request #21226 · webpack/webpack

bjohansebas · 2026-06-19T16:27:55Z

Summary

What kind of change does this PR introduce?

Did you add tests for your changes?

Does this PR introduce a breaking change?

If relevant, what needs to be documented once your changes are merged or what have you already documented?

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changeset-bot · 2026-06-19T16:28:00Z

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Latest commit: 06bb04b

The changes in this PR will be included in the next version bump.

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webpack	Minor

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codecov · 2026-06-19T16:35:03Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.81%. Comparing base (ecc00c0) to head (06bb04b).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #21226   +/-   ##
=======================================
  Coverage   92.80%   92.81%           
=======================================
  Files         591      592    +1     
  Lines       64726    64785   +59     
  Branches    18040    18050   +10     
=======================================
+ Hits        60072    60131   +59     
  Misses       4654     4654

Flag	Coverage Δ
css-parsing	`28.71% <0.00%> (-0.01%)`	⬇️
html5lib	`31.19% <39.34%> (+<0.01%)`	⬆️
integration	`88.97% <98.38%> (+0.03%)`	⬆️
test262	`45.40% <0.00%> (-0.01%)`	⬇️
unit	`41.49% <23.21%> (-0.02%)`	⬇️

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codspeed-hq · 2026-06-19T16:42:40Z

Merging this PR will not alter performance

⚠️

Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 2 improved benchmarks
❌ 2 regressed benchmarks
✅ 140 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	`BASE`	`HEAD`	Efficiency
❌	Memory	`benchmark "asset-modules-inline", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}'`	389.5 KB	1,230.7 KB	-68.35%
❌	Memory	`benchmark "many-chunks-esm", scenario '{"name":"mode-production","mode":"production"}'`	6.7 MB	8.7 MB	-22.62%
⚡	Memory	`benchmark "wasm-modules-async", scenario '{"name":"mode-development-rebuild","mode":"development","watch":true}'`	332.4 KB	248.2 KB	+33.91%
⚡	Memory	`benchmark "many-modules-commonjs", scenario '{"name":"mode-production","mode":"production"}'`	9.7 MB	7.4 MB	+32.14%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

_{Comparing bjohansebas:feat/html-iframe-srcdoc (06bb04b) with main (ecc00c0)}

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alexander-akait · 2026-06-20T02:19:33Z

We should not hardcode tags and attributes, it should be live in sources option by default, so other developers can apply this logic to other tags and attributes, also don’t forget, parsing srcdoc is not the same like html file by spec, there is an another logic, our parser is not fully ready for this, we need to introduce other function to parse it as I remember, verify it, also absolute URLs is already handled by output experimental option, don’t ignore them, the same for other types root relative and etc, no need to make todo because nothing to fix

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bjohansebas · 2026-06-20T03:34:22Z

+ * processed HTML read from the nested module's `html` code-generation data,
+ * re-escaped so the surrounding attribute stays valid.
+ */
+class HtmlInlineHtmlDependency extends ModuleDependency {


With this, it is not treated like a normal HTML document. Also, before that, the entire document is encoded to Base64

alexander-akait · 2026-06-22T11:56:13Z

@bjohansebas looks good, let's rebase and we can merge

bjohansebas · 2026-06-22T14:41:01Z

@alexander-akait done

alexander-akait · 2026-06-22T15:04:55Z

+			rules.push({
+				dependency: "html-srcdoc",
+				generator: {
+					extract: true


I am not sure we really need to extract here, but let's resolve it later, will investigate it in future

What if we add support for an "inline" string so I can simplify things?

alexander-akait · 2026-06-22T15:06:40Z

+									break;
+								}
+							}
+							if (inlineSrcdocOnly) continue;


This is bad code, it will be bad for performance, any extra loops for dependencies should be used only when no one other solution

yeah, on it for fix

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bjohansebas · 2026-06-22T16:26:14Z

Memoize the srcdoc-only check (HtmlModulesPlugin)
Fixture: 200 pages × 80 identical srcdocs shared across many chunks

Metric	Before	After	Improvement
Scan iterations/build	6,400,000	32,000	200× fewer
Time (median)	2553ms	2345ms	~8%
Retained memory	68.9MB	68.9MB	no change (zero overhead)

SRCDOC_ASSET_REGEXP pre-filter (HtmlParser)
Fixture: 120 pages × 60 asset-free formatting srcdocs

Metric	Before	After	Improvement
`data:text/html` modules	60	0	eliminated
Time (median)	1272ms	422ms	3× (~67%)
Peak heap	313MB	166MB	~47%
Retained memory	52.1MB	39.7MB	~24%

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bjohansebas · 2026-06-22T18:59:05Z

#21226 (comment)

With my change to extract "inline", the performance stays the same

alexander-akait · 2026-06-23T08:56:34Z

@bjohansebas sorry for extra rebase, can you do again and we can merge

… modules

…es and markup scenarios

… tests

…es and fix asset URL rewriting

…emplate

- Updated WebpackOptions.json to include `srcdoc` as a valid type for attribute parsing and bundling. - Modified HtmlParserOptions.check.js to validate `srcdoc` type in the HTML parser options. - Enhanced snapshot tests to cover new `srcdoc` functionality in iframe elements. - Created new test cases for handling `srcdoc` in custom tags and attributes. - Updated type definitions to reflect the addition of `srcdoc` in HtmlParserOptions and SourceType.

…es and update HTML parsing logic

…le connections

…upport and additional tests

…rcdoc>

- Updated WebpackOptions schema to allow "inline" as a valid option for the extract property, alongside boolean values. - Modified HtmlGeneratorOptions validation logic to accommodate the new "inline" option. - Adjusted unit tests to reflect the change in default extraction behavior from true to "inline". - Updated TypeScript definitions to include "inline" as a valid type for the extract property.

…s and configuration

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alexander-akait · 2026-06-23T16:58:34Z

Let’s fix lint, ignore bun, they are a little but unstable, WIP on it

…me-srcdoc

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github-actions · 2026-06-23T20:34:18Z

This PR is packaged and the instant preview is available (164a6ff).

Install it locally:

npm

npm i -D webpack@https://pkg.pr.new/webpack@164a6ff

yarn

yarn add -D webpack@https://pkg.pr.new/webpack@164a6ff

pnpm

pnpm add -D webpack@https://pkg.pr.new/webpack@164a6ff

bjohansebas marked this pull request as ready for review June 19, 2026 16:43

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bjohansebas commented Jun 20, 2026

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bjohansebas force-pushed the feat/html-iframe-srcdoc branch from 94d63be to 23fe0b7 Compare June 22, 2026 14:17

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bjohansebas force-pushed the feat/html-iframe-srcdoc branch from 23fe0b7 to 27b5d47 Compare June 22, 2026 16:14

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bjohansebas added 3 commits June 23, 2026 15:28

feat(html): implement asset URL rewriting for <iframe srcdoc> in HTML…

4180e2d

… modules

feat(html): enhance <iframe srcdoc> handling with additional test cas…

b71ee7a

…es and markup scenarios

feat(html): add support for CSS url() in <iframe srcdoc> and update…

793a32e

… tests

bjohansebas added 11 commits June 23, 2026 15:28

feat(html): enhance <iframe srcdoc> handling with additional test cas…

795bfa1

…es and fix asset URL rewriting

fixup!

4adda5f

feat(html): document plugin application in HtmlInlineHtmlDependency t…

8efc628

…emplate

feat(html): enhance <iframe srcdoc> handling with additional test cas…

4cefd0d

…es and update HTML parsing logic

feat(html): optimize inline srcdoc handling with memoization for modu…

dd74371

…le connections

feat(html): enhance <iframe srcdoc> handling with asset-free markup s…

65cbcc2

…upport and additional tests

feat(html): add tests and support for CSS processing inside <iframe s…

73cb7ce

…rcdoc>

feat(html): add support for inline srcdoc handling with new test case…

0b01ef1

…s and configuration

fixup!

3447067

bjohansebas force-pushed the feat/html-iframe-srcdoc branch from 3475434 to 3447067 Compare June 23, 2026 15:28

Copilot AI review requested due to automatic review settings June 23, 2026 16:07

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bjohansebas added 2 commits June 23, 2026 17:18

Merge branch 'main' of github.com:webpack/webpack into feat/html-ifra…

aa6881e

…me-srcdoc

fixup!

0e52f3c

bjohansebas force-pushed the feat/html-iframe-srcdoc branch from 1c7120f to 0e52f3c Compare June 23, 2026 17:19

Merge branch 'main' of github.com:webpack/webpack into feat/html-ifra…

06bb04b

…me-srcdoc

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alexander-akait approved these changes Jun 23, 2026

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alexander-akait merged commit 164a6ff into webpack:main Jun 23, 2026
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github-actions Bot mentioned this pull request Jun 23, 2026

chore(release): new release #21037

Merged

bjohansebas deleted the feat/html-iframe-srcdoc branch June 24, 2026 03:13

alexander-akait mentioned this pull request Jun 24, 2026

refactor(html): avoid regexp HTML parsing in dependencies; add <iframe srcdoc> script tests #21266

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