[flutter_tools] Implement Templates slice and flutter create integration by bkonyi · Pull Request #191748 · flutter/flutter

bkonyi · 2026-08-25T18:14:46Z

Description

This PR implements Step 5 of Flutter Tools Extensibility: the Templates extension slice and flutter create dynamic template integration.

Architectural Overview

package:flutter_tools_core:
- Defines core, platform-agnostic template models: ProjectTemplate and ExtensionProjectTemplate with JSON serialization, equality, and unordered set hashing.
package:flutter_tools_extension:
- Defines the TemplateService RPC interface and handlers for template.getAppTemplates, template.getPluginTemplates, template.getProjectTemplates, and template.generateTemplateParameters.
package:flutter_tools_extension_linux_prototype:
- Implements LinuxTemplateService and LinuxProjectTemplate declaring custom template 'custom-linux-app' with templateDependencies: {'app'}.
- Adds prototype template assets for 'custom-linux-app'.
packages/flutter_tools:
- Implements ExtensionTemplateManager to discover custom templates over RPC concurrently, cache them, resolve directories, and delegate parameter generation.
- Updates Template.fromDirectories to merge directory sources over base template dependencies.
- Integrates dynamic --template CLI options and help text into CreateCommand using ExtensionArgParserMixin.
- Supports ExtensionProjectTemplateType in FlutterProjectMetadata and ParsedFlutterTemplateType.
- Wires ExtensionTemplateManager through executable.dart into CreateCommand.

Related Issues

Part of #190692

Tests

Added packages/flutter_tools/packages/flutter_tools_core/test/templates_test.dart
Added packages/flutter_tools/packages/flutter_tools_extension_linux_prototype/test/linux_template_test.dart
Added packages/flutter_tools/test/general.shard/extension_protocol/template_service_test.dart
Updated packages/flutter_tools/test/general.shard/flutter_project_metadata_test.dart
Updated packages/flutter_tools/test/integration.shard/tool_extensions_test.dart

Implements the Templates extension service and integrates dynamic custom template support into `flutter create` and `package:flutter_tools_core`. - `package:flutter_tools_core`: - Adds `ProjectTemplate` and `ExtensionProjectTemplate` domain models with JSON serialization, hashing, and equality in `lib/src/templates.dart`. - Exports template models from `lib/flutter_tools_core.dart`. - `package:flutter_tools_extension`: - Defines `TemplateService` RPC interface and handlers for `template.getAppTemplates`, `template.getPluginTemplates`, `template.getProjectTemplates`, and `template.generateTemplateParameters` in `lib/src/templates.dart`. - `package:flutter_tools_extension_linux_prototype`: - Implements `LinuxTemplateService` and `LinuxProjectTemplate` declaring custom template `'custom-linux-app'` with `templateDependencies: {'app'}`. - Adds prototype template assets for `'custom-linux-app'`. - `packages/flutter_tools`: - Adds `ExtensionTemplateManager` in `lib/src/experimental/templates.dart` to discover custom templates over RPC, cache them, resolve directories, and delegate parameter generation. - Updates `Template.fromDirectories` in `lib/src/template.dart` to merge directory sources with base template dependencies. - Updates `CreateCommand` and `ExtensionArgParserMixin` to dynamically populate `--template` CLI options and help entries. - Updates `FlutterProjectMetadata` and `ParsedFlutterTemplateType` to support `ExtensionProjectTemplateType`. - Wires `ExtensionTemplateManager` through `executable.dart` into `CreateCommand`. - Adds unit, hermetic usage, and integration test coverage across all layers.

… integration test

gemini-code-assist

Code Review

This pull request introduces support for custom project templates provided dynamically by tool extensions in flutter create. It adds ExtensionTemplateManager to query templates over RPC, updates CreateCommand to dynamically rebuild its argument parser, and integrates custom template rendering. The review feedback suggests wrapping asynchronous RPC calls to getProjectTemplates() in try-catch blocks to prevent potential tool crashes if extensions fail to initialize. Additionally, it recommends adding a fallback mechanism when parsing custom template names from .metadata files to handle scenarios where the extension manager is not active.

…t metadata

…plates-slice # Conflicts: # packages/flutter_tools/lib/src/experimental/extension_arg_parser.dart

…in CreateCommand

…plates.dart Co-authored-by: Loïc Sharma <[email protected]>

loic-sharma · 2026-09-01T02:34:43Z

+    return ExtensionArgParserMixin.cloneParser(
+      baseArgParser,
+      optionCloner: (ArgParser newParser, Option opt) {
+        if (opt.name == 'template') {


Nit: Consider inverting this to improve readability. Something like:

if (opt.name != 'template') { ExtensionArgParserMixin.copyOption(newParser, opt); return; } // Template logic here...

I don't feel strongly, feel free to skip.

loic-sharma · 2026-09-01T02:46:28Z

      );
+      if (parsedTemplate == null) {
+        throwToolExit(
+          'Expected one of ${ParsedFlutterTemplateType.enabledValues(featureFlags, extensionTemplateManager: _extensionTemplateManager).map((ParsedFlutterTemplateType t) => t.cliName).join(', ')} '


Nit: consider splitting this into two lines, it's quite long

loic-sharma · 2026-09-01T02:54:54Z

+          if (depTemplate != null) {
+            templateSources.add(manager.resolveTemplateDirectory(depTemplate.templatePath));
+          } else {
+            // Fallback to internal templates.


Should we make internal templates have higher priority than extension templates? I suspect allowing extensions to override internal templates is not a scenario we want to support?

loic-sharma · 2026-09-01T03:00:43Z

+  static ParsedFlutterTemplateType? fromCliName(
+    String cliName, {
+    required ExtensionTemplateManager? extensionTemplateManager,
+    bool fallbackToCustom = false,


FYI this appears to be unused currently, other than in tests. Is it still needed?

…and CreateCommand

…anch

…move unused fallbackToCustom

…plates.dart Co-authored-by: Loïc Sharma <[email protected]>

loic-sharma · 2026-09-01T03:12:04Z

 import 'doctor.dart';
 import 'emulator.dart';
 import 'features.dart';
+


This looks like an unintentional change :)

Probably had some changes here before... 😅

…traneous newline in context_runner

…Hub review

loic-sharma · 2026-09-01T03:34:29Z

+    throw UnimplementedError(
+      'ExtensionProjectTemplate.generateTemplateParameters should not be called directly on host representation.',
+    );
+  }


(Sorry for re-litigating 😂)

I still don't love this pattern. Over time, I expect we'll have lots of methods that the host should not call, but if we make a mistake in the host it'll be non-obvious from the call site. I'm OK with landing this, but this pattern is something I think we should reconsider after we've landed more of the prototype.

Completely agree!

loic-sharma · 2026-09-01T03:39:09Z

+      'ExtensionProjectTemplate(name: $name, hidden: $hidden, templateDependencies: $templateDependencies, templateSources: $templateSources, templatePath: $templatePath)';
+
+  @override
+  bool operator ==(Object other) {


Just curious, why do we need to override == and hashCode for the host side models again?

Mainly for unit test assertions so we can do expect(actual, expected).

Ah OK sounds good 👍

loic-sharma

This looks good to me! All feedback is minor nitpicks :)

auto-submit · 2026-09-01T17:24:57Z

autosubmit label was removed for flutter/flutter/191748, because - The status or check suite Dashboard Checks has failed. Please fix the issues identified (or deflake) before re-applying this label.

flutter/flutter@0cbd1a4...70797e1 2026-09-02 [email protected] [analysis] Upgrade package:analyzer to 14.3.0 and enable custom plugin compilation (flutter/flutter#191590) 2026-09-02 [email protected] Roll Dart SDK from d8d7869d8031 to 9a8fbde80f6c (1 revision) (flutter/flutter#192179) 2026-09-02 [email protected] Roll Skia from dec311244db4 to ae22da2e8308 (1 revision) (flutter/flutter#192177) 2026-09-02 [email protected] [tool] Migrate DoctorCommand to modular dependency injection (flutter/flutter#190758) 2026-09-02 [email protected] Roll Skia from 482b7e285244 to dec311244db4 (3 revisions) (flutter/flutter#192161) 2026-09-02 [email protected] Roll Skia from 28447e9fb8d5 to 482b7e285244 (3 revisions) (flutter/flutter#192157) 2026-09-02 [email protected] feat: Add placeholder to DecorationImage (flutter/flutter#191528) 2026-09-02 [email protected] [Android] Do not schedule engine frames on a detached FlutterJNI (flutter/flutter#191204) 2026-09-02 [email protected] Roll Skia from 3a242fb7cdb3 to 28447e9fb8d5 (1 revision) (flutter/flutter#192145) 2026-09-02 [email protected] Roll Dart SDK from 9164def35347 to d8d7869d8031 (2 revisions) (flutter/flutter#192144) 2026-09-02 [email protected] Add FadeInImageTransition.fadeInOver to fade the image in over the placeholder (flutter/flutter#186246) 2026-09-02 [email protected] Roll Skia from 63d13ec4df6d to 3a242fb7cdb3 (9 revisions) (flutter/flutter#192138) 2026-09-02 [email protected] [flutter_tools] Add --no-plugins flag and disable plugins for benchmark (flutter/flutter#192129) 2026-09-02 [email protected] [tool] Migrate ChannelCommand to modular dependency injection (flutter/flutter#190751) 2026-09-01 [email protected] Add mouseCursor to RawScrollbar (flutter/flutter#185750) 2026-09-01 [email protected] Fix self-comparison and assert typos in TestSemantics (flutter/flutter#191938) 2026-09-01 [email protected] [Linux] Wait for frames to be rendered before using them in another context (flutter/flutter#192094) 2026-09-01 [email protected] [wimp] Turn on multithreading for wimp. (flutter/flutter#191747) 2026-09-01 [email protected] Roll Skia from 3911a1fe7f7a to 63d13ec4df6d (6 revisions) (flutter/flutter#192125) 2026-09-01 [email protected] Remove the redundant flutter/shell/platform/android:robolectric_tests build target (flutter/flutter#192117) 2026-09-01 [email protected] [iOS] Preserve semantics parents after reparenting (flutter/flutter#189686) 2026-09-01 [email protected] [flutter_tools] Report preview reload timing analytics in LspPreviewDetector (flutter/flutter#192120) 2026-09-01 [email protected] [flutter_tools] Implement Templates slice and flutter create integration (flutter/flutter#191748) 2026-09-01 [email protected] Uiscene migrate add2app hosts (flutter/flutter#191847) 2026-09-01 [email protected] Roll Packages from d642322 to 7a7912f (8 revisions) (flutter/flutter#192119) 2026-09-01 [email protected] [web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset (flutter/flutter#190486) 2026-09-01 [email protected] Replace Shell::WaitForFirstFrame with an asynchronous API that matches the Shell threading model (flutter/flutter#191841) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

…r#12727) flutter/flutter@0cbd1a4...70797e1 2026-09-02 [email protected] [analysis] Upgrade package:analyzer to 14.3.0 and enable custom plugin compilation (flutter/flutter#191590) 2026-09-02 [email protected] Roll Dart SDK from d8d7869d8031 to 9a8fbde80f6c (1 revision) (flutter/flutter#192179) 2026-09-02 [email protected] Roll Skia from dec311244db4 to ae22da2e8308 (1 revision) (flutter/flutter#192177) 2026-09-02 [email protected] [tool] Migrate DoctorCommand to modular dependency injection (flutter/flutter#190758) 2026-09-02 [email protected] Roll Skia from 482b7e285244 to dec311244db4 (3 revisions) (flutter/flutter#192161) 2026-09-02 [email protected] Roll Skia from 28447e9fb8d5 to 482b7e285244 (3 revisions) (flutter/flutter#192157) 2026-09-02 [email protected] feat: Add placeholder to DecorationImage (flutter/flutter#191528) 2026-09-02 [email protected] [Android] Do not schedule engine frames on a detached FlutterJNI (flutter/flutter#191204) 2026-09-02 [email protected] Roll Skia from 3a242fb7cdb3 to 28447e9fb8d5 (1 revision) (flutter/flutter#192145) 2026-09-02 [email protected] Roll Dart SDK from 9164def35347 to d8d7869d8031 (2 revisions) (flutter/flutter#192144) 2026-09-02 [email protected] Add FadeInImageTransition.fadeInOver to fade the image in over the placeholder (flutter/flutter#186246) 2026-09-02 [email protected] Roll Skia from 63d13ec4df6d to 3a242fb7cdb3 (9 revisions) (flutter/flutter#192138) 2026-09-02 [email protected] [flutter_tools] Add --no-plugins flag and disable plugins for benchmark (flutter/flutter#192129) 2026-09-02 [email protected] [tool] Migrate ChannelCommand to modular dependency injection (flutter/flutter#190751) 2026-09-01 [email protected] Add mouseCursor to RawScrollbar (flutter/flutter#185750) 2026-09-01 [email protected] Fix self-comparison and assert typos in TestSemantics (flutter/flutter#191938) 2026-09-01 [email protected] [Linux] Wait for frames to be rendered before using them in another context (flutter/flutter#192094) 2026-09-01 [email protected] [wimp] Turn on multithreading for wimp. (flutter/flutter#191747) 2026-09-01 [email protected] Roll Skia from 3911a1fe7f7a to 63d13ec4df6d (6 revisions) (flutter/flutter#192125) 2026-09-01 [email protected] Remove the redundant flutter/shell/platform/android:robolectric_tests build target (flutter/flutter#192117) 2026-09-01 [email protected] [iOS] Preserve semantics parents after reparenting (flutter/flutter#189686) 2026-09-01 [email protected] [flutter_tools] Report preview reload timing analytics in LspPreviewDetector (flutter/flutter#192120) 2026-09-01 [email protected] [flutter_tools] Implement Templates slice and flutter create integration (flutter/flutter#191748) 2026-09-01 [email protected] Uiscene migrate add2app hosts (flutter/flutter#191847) 2026-09-01 [email protected] Roll Packages from d642322 to 7a7912f (8 revisions) (flutter/flutter#192119) 2026-09-01 [email protected] [web] Anchor flt-semantics-host at 0,0 to fix WebKit semantics offset (flutter/flutter#190486) 2026-09-01 [email protected] Replace Shell::WaitForFirstFrame with an asynchronous API that matches the Shell threading model (flutter/flutter#191841) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected] on the revert to ensure that a human is aware of the problem. To file a bug in Packages: https://github.com/flutter/flutter/issues/new/choose To report a problem with the AutoRoller itself, please file a bug: https://issues.skia.org/issues/new?component=1389291&template=1850622 Documentation for the AutoRoller is here: https://skia.googlesource.com/buildbot/+doc/main/autoroll/README.md

github-actions Bot added tool Affects the "flutter" command-line tool. See also t: labels. team-ios Owned by iOS platform team team-macos Owned by the macOS platform team team-linux Owned by the Linux platform team labels Aug 25, 2026

bkonyi added the CICD Run CI/CD label Aug 25, 2026

bkonyi force-pushed the ft-ext-step05-templates-slice branch from c69e665 to 1106827 Compare August 26, 2026 01:37

github-actions Bot removed team-ios Owned by iOS platform team team-macos Owned by the macOS platform team labels Aug 26, 2026

[flutter_tools] Fix custom template platform check in tool extensions…

e490e09

… integration test

bkonyi marked this pull request as ready for review August 26, 2026 03:26

bkonyi requested a review from a team as a code owner August 26, 2026 03:26

bkonyi removed the request for review from a team August 26, 2026 03:26

gemini-code-assist Bot reviewed Aug 26, 2026

View reviewed changes

Comment thread packages/flutter_tools/lib/src/commands/create.dart

Comment thread packages/flutter_tools/lib/src/commands/create.dart

Comment thread packages/flutter_tools/lib/src/flutter_project_metadata.dart

Comment thread packages/flutter_tools/lib/src/flutter_project_metadata.dart

bkonyi added 2 commits August 26, 2026 03:31

[flutter_tools] Fall back to custom template type when parsing projec…

916630f

…t metadata

[flutter_tools] Do not fall back to custom template type in parseYaml

42f0b7f

bkonyi requested a review from loic-sharma August 26, 2026 15:34

bkonyi added 2 commits August 28, 2026 14:36

Merge remote-tracking branch 'upstream/master' into ft-ext-step05-tem…

5f0882c

…plates-slice # Conflicts: # packages/flutter_tools/lib/src/experimental/extension_arg_parser.dart

[flutter_tools] Handle extension template lookup failures gracefully …

431bc07

…in CreateCommand