fix: resolve issue #177379 by using lazy buildDirectory.dir() API in build.gradle template by mboetger · Pull Request #187127 · flutter/flutter

mboetger · 2026-05-26T21:05:17Z

Executive Triage & Resolution Report: Issue #177379

A comprehensive report on the end-to-end lifecycle of reproducing and resolving GitHub issue flutter/flutter#177379.

1. Executive Summary

GitHub Issue: flutter/flutter#177379
Problem Description: When building an Android App Bundle (.aab) with deferred components, the Dart code split works, but all declared assets/JNI libraries in the dynamic feature modules are missing from the final .aab.
Triage Diagnosis: The root cause is a property coercion bug in the Gradle templates where project.layout.buildDirectory (which is a lazy DirectoryProperty in Gradle 7.x/8.x+) was evaluated inside double-quoted Groovy GStrings ("${project.layout.buildDirectory}/..."). Groovy coerced this property into a debug string descriptor (e.g. "property(org.gradle.api.file.Directory, ...)"), pointing Gradle to an invalid path. Consequently, Gradle silently ignored and skipped packaging the assets and JNI library directories.
Resolution Details: The template and affected integration test configurations were updated to use the native lazy Gradle subdirectory API: project.layout.buildDirectory.dir(...). A new unit test has been added to ensure this template maintains correct lazy API usage and prevents regression.
Status: All unit and integration tests pass successfully on triage-issue-177379 branch. The changes have been fully approved by peer reviewer agents and committed.

2. Root Cause Analysis & Technical Deep Dive

In Gradle 7.x/8.x+, project.layout.buildDirectory represents a DirectoryProperty. It is designed to be evaluated lazily to allow late modification of build output pathways.

The Problematic Code (Before)

sourceSets {
    applicationVariants.all { variant ->
        main.assets.srcDirs += "${project.layout.buildDirectory}/intermediates/flutter/${variant.name}/deferred_assets"
        main.jniLibs.srcDirs += "${project.layout.buildDirectory}/intermediates/flutter/${variant.name}/deferred_libs"
    }
}

When Groovy parses "${project.layout.buildDirectory}/...", it calls .toString() on the DirectoryProperty during GString evaluation. Instead of resolving to the build path (e.g. build/), it coerces to property(org.gradle.api.file.Directory, property(org.gradle.api.file.Directory, ...))/intermediates/flutter/release/deferred_assets. Since Gradle does not find this directory, it silently skips it, leading to empty dynamic feature asset bundles.

The Solution (After)

sourceSets {
    applicationVariants.all { variant ->
        main.assets.srcDirs += project.layout.buildDirectory.dir("intermediates/flutter/${variant.name}/deferred_assets")
        main.jniLibs.srcDirs += project.layout.buildDirectory.dir("intermediates/flutter/${variant.name}/deferred_libs")
    }
}

By calling .dir(...), we obtain a provider of Directory, which is evaluated correctly during the execution phase of Gradle when assets and JNI libraries are gathered.

Fixes: #177379

Pre-launch Checklist

gemini-code-assist

Code Review

This pull request updates Gradle build files and templates to use the lazy DirectoryProperty.dir(...) API instead of resolving the build directory eagerly. It also adds a unit test to verify this template structure. The review feedback suggests avoiding direct usage of dart:io and io.File in flutter_tools tests, recommending the use of package:file/file.dart and package:file/local.dart instead to maintain test hermeticity.

reidbaker

The tests test the wrong thing but the fix seems reasonable.

Blocking because we do not want to verify that we use the new behavior. We want a test that shows that the bug is resolved. That will likely involve creating an aab that is exhibits to this bug and verifying that assets are present.

…API in build.gradle template

…ies and using lazy directory providers - Update deferred component Gradle template and test configurations to use lazy directory providers (project.layout.buildDirectory.dir(...)) instead of eager GString string coercion, preventing incorrect build path evaluation. - Configure dynamic feature subprojects to explicitly depend on flutterCompileTask for their assets and native libraries merging tasks (mergeVariantAssets and mergeVariantJniLibFolders), resolving parallel build race conditions during clean builds.

gmackall

I wasn't at the bug bash but was this verified to fix the linked issue? Based on the test it would seem like yes?

If so lgtm

gmackall

reapprove

mboetger · 2026-06-01T20:49:49Z

I wasn't at the bug bash but was this verified to fix the linked issue? Based on the test it would seem like yes?

If so lgtm

So, triage bot correctly identified the fix - the lazy buildDirectory is correct. I verified this manually: letanssang/test_dynamic_module#3

I had to verify it manually because the tests do not correctly repro the issue. I even removed the FlutterPlugin change, because that was added with the test.

The repro test passes on master - currently trying to come up with a better test.

mboetger · 2026-06-01T22:01:28Z

Ok, I figured out why the test pass on master and the issue exists. The test actually is setup correctly - and DIFFERENTLY - from the template:

flutter/dev/integration_tests/deferred_components_test/android/component1/build.gradle

Lines 32 to 33 in 308649c

    
           main.assets.srcDirs += "${project.layout.buildDirectory.get()}/intermediates/flutter/${variant.name}/deferred_assets" 
        
           main.jniLibs.srcDirs += "${project.layout.buildDirectory.get()}/intermediates/flutter/${variant.name}/deferred_libs"

The configuration uses the .get() call.

The template does not use the .get() call.

flutter/packages/flutter_tools/templates/module/android/deferred_component/build.gradle.tmpl

Lines 32 to 33 in 643bafc

    
           main.assets.srcDirs += "${project.layout.buildDirectory}/intermediates/flutter/${variant.name}/deferred_assets" 
        
           main.jniLibs.srcDirs += "${project.layout.buildDirectory}/intermediates/flutter/${variant.name}/deferred_libs"

So, I believe the test being added still is somewhat valuable - even if it passes on master. The important part is the test now matches the actual template.

mboetger · 2026-06-01T22:27:40Z

@reidbaker - Can you take a look at the test and the above comments and see if it fits your requested changes?

reidbaker

Thanks for removing the change detector tests

Roll Flutter from 2ba5420a7049 to 1bdf4af29076 (43 revisions) flutter/flutter@2ba5420...1bdf4af 2026-06-05 engine-flutter-autoroll@skia.org Roll Packages from 03352b5 to 61bdbb4 (5 revisions) (flutter/flutter#187612) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 6e003d7f69c8 to a47a9a2c8ae5 (1 revision) (flutter/flutter#187610) 2026-06-05 engine-flutter-autoroll@skia.org Roll Dart SDK from aad8be4ce307 to 6a9a0efe66eb (10 revisions) (flutter/flutter#187609) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 494f1bf55f51 to 6e003d7f69c8 (2 revisions) (flutter/flutter#187607) 2026-06-05 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ZE1Jy9CtVVi-tjBAE... to N_LiSaBSUsE2LDZgG... (flutter/flutter#187597) 2026-06-05 engine-flutter-autoroll@skia.org Roll Skia from 59556fdb8c33 to 494f1bf55f51 (2 revisions) (flutter/flutter#187596) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 8eb107046fd5 to 59556fdb8c33 (1 revision) (flutter/flutter#187590) 2026-06-04 34871572+gmackall@users.noreply.github.com Remove `embedded_android_views_integration_test.dart` (flutter/flutter#187465) 2026-06-04 burak.karahan@mail.ru Remove Material imports from rendering editable tests (flutter/flutter#186951) 2026-06-04 jason-simmons@users.noreply.github.com [Impeller] Wait for the Vulkan device to become idle before destroying Vulkan objects in the AHBSwapchainImplVK destructor (flutter/flutter#187477) 2026-06-04 chris@bracken.jp [iOS] Eliminate unnecessary redeclaration of FlutterDisplayLink (flutter/flutter#187557) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 928ded2a31af to 8eb107046fd5 (1 revision) (flutter/flutter#187583) 2026-06-04 34871572+gmackall@users.noreply.github.com Log stdout in adb.dart (flutter/flutter#187531) 2026-06-04 mvincentong@gmail.com Clarify RouterDelegate popRoute bubbling (flutter/flutter#186875) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 928ded2a31af to 8eb107046fd5 (1 revision) (flutter/flutter#187584) 2026-06-04 1063596+reidbaker@users.noreply.github.com Add updating-android-sdk agent skill for rolling Android SDK in CIPD (flutter/flutter#187576) 2026-06-04 Rusino@users.noreply.github.com Fixing alignment issue (flutter/flutter#187518) 2026-06-04 brackenavaron@gmail.com [Material Cross Imports] Clean up Material Divider usages (flutter/flutter#187300) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from cecc0e0da9ae to 928ded2a31af (6 revisions) (flutter/flutter#187574) 2026-06-04 31859944+LongCatIsLooong@users.noreply.github.com Use swift demangle to verify internal Swift symbols (flutter/flutter#186835) 2026-06-04 1063596+reidbaker@users.noreply.github.com Add android 37 platform and build tools to script for android cipd bundle creation (flutter/flutter#187571) 2026-06-04 jason-simmons@users.noreply.github.com [Impeller] Increase the precision of the IPSampleWithTileModeOES coords parameter to match the input coordinates in the tiled_texture_fill_external shader (flutter/flutter#187545) 2026-06-04 engine-flutter-autoroll@skia.org Roll Packages from b11504f to 03352b5 (4 revisions) (flutter/flutter#187569) 2026-06-04 iinozemtsev@google.com Roll Dart SDK to Dart 3.13 beta2 (flutter/flutter#187555) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 611e3f8ceb93 to cecc0e0da9ae (1 revision) (flutter/flutter#187562) 2026-06-04 6655696+guidezpl@users.noreply.github.com Add step to bootstrap Flutter tool in coverage workflow (flutter/flutter#187199) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 4fdb859c8da7 to 611e3f8ceb93 (4 revisions) (flutter/flutter#187554) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from 0020aae33f63 to 4fdb859c8da7 (2 revisions) (flutter/flutter#187552) 2026-06-04 engine-flutter-autoroll@skia.org Roll Fuchsia Linux SDK from ap7MhLX4TdpWRrLS_... to ZE1Jy9CtVVi-tjBAE... (flutter/flutter#187550) 2026-06-04 stuartmorgan@google.com Add vector_math to package issue template (flutter/flutter#187536) 2026-06-04 jason-simmons@users.noreply.github.com Manual roll Dart SDK from d39850bf4a01 to 3b70b98fa7c0 (flutter/flutter#187519) 2026-06-04 engine-flutter-autoroll@skia.org Roll Skia from d625048c853a to 0020aae33f63 (20 revisions) (flutter/flutter#187539) 2026-06-04 smille2003@yandex.ru [Impeller][Windows] fix black screen on OpenGL fallback (flutter/flutter#187288) 2026-06-04 97480502+b-luk@users.noreply.github.com Fix unintentionally joined path contours (flutter/flutter#187522) 2026-06-03 matt.boetger@gmail.com fix: resolve issue #177379 by using lazy buildDirectory.dir() API in build.gradle template (flutter/flutter#187127) 2026-06-03 34871572+gmackall@users.noreply.github.com Add a skill for flake analysis (flutter/flutter#187530) 2026-06-03 30870216+gaaclarke@users.noreply.github.com adds linux impeller project flag (flutter/flutter#186982) 2026-06-03 codedoctor@linwood.dev Add support for stylus buttons (flutter/flutter#183369) 2026-06-03 46920873+gabrimatic@users.noreply.github.com Prevent Cubic transform from looping on out-of-range input (flutter/flutter#185875) 2026-06-03 bdero@google.com [Impeller] Reland: Allow attaching specific texture mip levels and slices (flutter/flutter#187470) 2026-06-03 kjlubick@users.noreply.github.com [skia] Update image deserial proc (flutter/flutter#185041) 2026-06-03 112751483+shivanshu877@users.noreply.github.com docs: update Impeller advanced blend docs for framebuffer fetch (flutter/flutter#185457) 2026-06-03 ahmedsameha1@gmail.com Handle#6537 fifth grouped tests (flutter/flutter#183720) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: ...

flutter-dashboard Bot added the CICD Run CI/CD label May 26, 2026

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Comment thread ...es/flutter_tools/test/general.shard/android/deferred_components_prebuild_validator_test.dart Outdated

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mboetger added 2 commits May 29, 2026 23:06

fix: resolve issue flutter#177379 by using lazy buildDirectory.dir() …

6500bf9

…API in build.gradle template

mboetger force-pushed the triage-issue-177379 branch from 220c0d1 to c6ac19f Compare May 29, 2026 23:08

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Merge branch 'master' into triage-issue-177379

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remove flutterplugin fix

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Merge branch 'master' into triage-issue-177379

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Merge branch 'master' into triage-issue-177379

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remove change detector test

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adjust wording of test

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fix: resolve issue #177379 by using lazy buildDirectory.dir() API in build.gradle template#187127

fix: resolve issue #177379 by using lazy buildDirectory.dir() API in build.gradle template#187127
auto-submit[bot] merged 8 commits into
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mboetger commented May 26, 2026 •

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Executive Triage & Resolution Report: Issue #177379

1. Executive Summary

2. Root Cause Analysis & Technical Deep Dive

The Problematic Code (Before)

The Solution (After)

Pre-launch Checklist

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mboetger commented May 26, 2026 •

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