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[flutter_tools] Reland fix for local CanvasKit asset paths on Windows - #195770

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molchanovia:fix/canvaskit-windows-reland
Nov 5, 2026
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auto-submit[bot] merged 2 commits into
flutter:masterfrom
molchanovia:fix/canvaskit-windows-reland

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@molchanovia

@molchanovia molchanovia commented Nov 1, 2026 •

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Relands #193776, reverted by #195635.

On Windows, converting a CanvasKit request URI to a filesystem path before matching canvaskit/ causes valid asset requests to return HTTP 404. Match URI path segments first, then construct and validate the filesystem path. Restore regression coverage for POSIX and Windows paths, including JavaScript/Wasm assets, response bodies and headers, and invalid paths.

The regression tests now pass MustacheTemplateRenderer to FlutterWebPlatform.start, addressing the required templateRenderer parameter introduced by #194062 that caused the original tree breakage.

Fixes #193505.

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@github-actions github-actions Bot added the tool Affects the "flutter" command-line tool. See also t: labels. label Nov 1, 2026
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molchanovia marked this pull request as ready for review November 1, 2026 17:57

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Code Review

This pull request refactors how local CanvasKit assets are resolved and served in FlutterWebPlatform, replacing string-based path manipulation with structured path segments and adding validation checks to prevent directory traversal. It also introduces a comprehensive test suite to verify CanvasKit asset serving across POSIX and Windows path styles. The feedback suggests optimizing the handler by performing an early return check on the first path segment before constructing the full file path.

Reland flutter#193776, reverted by flutter#195635. Match CanvasKit requests by URI path
segments before constructing filesystem paths, preserving containment
checks and POSIX/Windows regression coverage.

Pass MustacheTemplateRenderer to FlutterWebPlatform.start in the regression
tests to satisfy the required templateRenderer parameter added by flutter#194062.
@molchanovia
molchanovia force-pushed the fix/canvaskit-windows-reland branch from dec6d99 to 294be75 Compare November 1, 2026 17:59
@bkonyi
bkonyi requested review from bkonyi and mdebbar November 4, 2026 20:27
@bkonyi bkonyi added the CICD Run CI/CD label Nov 4, 2026

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LGTM! Thanks for creating the reland!

@mdebbar mdebbar left a comment

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Thanks for the reland, LGTM!

@mdebbar mdebbar added the autosubmit Merge PR when tree becomes green via auto submit App label Nov 5, 2026
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auto-submit Bot added this pull request to the merge queue Nov 5, 2026
Merged via the queue into flutter:master with commit 933dbf2 Nov 5, 2026
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@flutter-dashboard flutter-dashboard Bot removed the autosubmit Merge PR when tree becomes green via auto submit App label Nov 5, 2026
auto-submit Bot pushed a commit to flutter/packages that referenced this pull request Nov 6, 2026
Roll Flutter from 3623d2d34543 to 09175cdeac89 (61 revisions)

flutter/flutter@3623d2d...09175cd

2026-11-06 [email protected] Roll Skia from ae35b7b2221f to 793b8ac73d4b (3 revisions) (flutter/flutter#196091)
2026-11-06 [email protected] [web] Rasterize scenes at the size passed to `FlutterView.render` (flutter/flutter#196052)
2026-11-06 [email protected] Roll Skia from 4aa043a81e0c to ae35b7b2221f (1 revision) (flutter/flutter#196086)
2026-11-06 [email protected] Roll Fuchsia Linux SDK from Fqe3UlLwAohsPbsCS... to KIc0XZbhLmvDpTluZ... (flutter/flutter#196085)
2026-11-06 [email protected] Allow a zero scale change in InteractiveViewer (flutter/flutter#194949)
2026-11-06 [email protected] Roll Skia from dd5c2553a856 to 4aa043a81e0c (2 revisions) (flutter/flutter#196079)
2026-11-06 [email protected] [web] Keep ImageFilter.blur bounds in equality and description (flutter/flutter#196013)
2026-11-06 [email protected] iOS: Remove unused PlatformViewIOS setup from FlutterPlatformViewsTest (flutter/flutter#196033)
2026-11-06 [email protected] Serialize LoggerTests that mutate the shared Logger (flutter/flutter#196028)
2026-11-06 [email protected] Use reverseDuration for the AnimatedCrossFade size animation (flutter/flutter#194860)
2026-11-05 [email protected] Roll Skia from a5aacd103e68 to dd5c2553a856 (8 revisions) (flutter/flutter#196073)
2026-11-05 [email protected] Fix ListWheelScrollView null check error when it reads itemIndex before content dimensions are set (flutter/flutter#194859)
2026-11-05 [email protected] Allow zero cross axis extent in SliverGridDelegateWithMaxCrossAxisExtent (flutter/flutter#194858)
2026-11-05 [email protected] Revert: Allow color delta tolerance in in-memory fuzzy image comparator (flutter/flutter#196067)
2026-11-05 [email protected] Revert: Mitigate snapshot race in 3D transform test by reducing loop density (flutter/flutter#196066)
2026-11-05 [email protected] Delegate createStream in ResizeImage and ScrollAwareImageProvider (flutter/flutter#194756)
2026-11-05 [email protected] [iOS] Introduce FlutterShell and move thread host and profiler (flutter/flutter#195388)
2026-11-05 [email protected] [web] Support FragmentShader.getImageSampler on CanvasKit and Skwasm (flutter/flutter#195854)
2026-11-05 [email protected] Deprecates setFloat API (flutter/flutter#195505)
2026-11-05 [email protected] [flutter_tools] Remove public GlobalToolContext and globals from runner (flutter/flutter#195561)
2026-11-05 [email protected] Defer TLHC PlatformViewWrapper frame post and avoid initial 1x1 buffer resize (flutter/flutter#195861)
2026-11-05 [email protected] Roll Skia from b5abed66da86 to a5aacd103e68 (17 revisions) (flutter/flutter#196054)
2026-11-05 [email protected] Made `FlutterWindowControllerSizeTest.SizedToContentNotResizable` more robust (flutter/flutter#195845)
2026-11-05 [email protected] Update docs for contributor ladder (flutter/flutter#196011)
2026-11-05 [email protected] [Impeller] Use the transfer stage for the Vulkan readback barrier (flutter/flutter#194991)
2026-11-05 [email protected] Remove Mac mac_unopt builder (flutter/flutter#196027)
2026-11-05 [email protected] Updated Instructions for Determining Gradle Version for `gradle_dists` in CIPD (flutter/flutter#193310)
2026-11-05 [email protected] Move ios_app_with_extensions_test into the tool integration shard (flutter/flutter#195609)
2026-11-05 [email protected] [web] Respect Uint8List view bounds when detecting animated WebP/GIF (flutter/flutter#196010)
2026-11-05 [email protected] Add platform_views_layout to build_tests so iOS/Android build breaks are caught in presubmit (flutter/flutter#192985)
2026-11-05 [email protected] [flutter_tools] Detect macOS TCC permission crashes and provide diagnostic guidance (flutter/flutter#192432)
2026-11-05 [email protected] Roll Packages from 670b30e to 0478162 (15 revisions) (flutter/flutter#196047)
2026-11-05 [email protected] [web] Support Skwasm rendering without bitmap capture (flutter/flutter#195103)
2026-11-05 [email protected] [flutter_tools] Reland fix for local CanvasKit asset paths on Windows (flutter/flutter#195770)
2026-11-05 [email protected] Roll Skia from f96be51af95d to b5abed66da86 (14 revisions) (flutter/flutter#196017)
2026-11-05 [email protected] Split chrome web engine test drone (flutter/flutter#195873)
2026-11-05 [email protected] Roll Dart SDK from c9153304136a to 6623b84628f3 (1 revision) (flutter/flutter#196026)
2026-11-05 [email protected] Roll ICU from 4fe960221710 to a0ea93436c52 (6 revisions) (flutter/flutter#196025)
2026-11-05 [email protected] Add more guidance in README and AGENTS for contributing to flutter_tools (flutter/flutter#195998)
2026-11-05 [email protected] Roll Fuchsia Linux SDK from p0HDXLISPIElJfSz7... to Fqe3UlLwAohsPbsCS... (flutter/flutter#196019)
2026-11-05 [email protected] Roll Dart SDK from e362a23e9738 to c9153304136a (18 revisions) (flutter/flutter#196014)
2026-11-05 [email protected] [Impeller] Fix dilation input bounds when clipping saveLayers (flutter/flutter#195652)
2026-11-05 [email protected] Add `variantOf` to the M3E migration checklist (flutter/flutter#195099)
2026-11-05 [email protected] [flutter_tools] Eliminate globals from remaining subsystem files (flutter/flutter#195555)
2026-11-05 [email protected] Fix gap flipping when dragging variable height reorderable items (flutter/flutter#194478)
2026-11-05 [email protected] [A11y] Send un-merged SemanticsNodes in the same update that first references them (flutter/flutter#195829)
...
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flutter test --platform chrome hangs/fails on Windows: CanvasKit assets 404 due to backslash path from path.fromUri

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