FlutterGen logs SEVERE when a build.yaml exists without FlutterGen options (config lives in pubspec.yaml)

[behnamsattar]

If a package has a build.yaml for other builders and keeps FlutterGen configuration in pubspec.yaml (as documented), running build_runner prints:

[SEVERE] FlutterGen:
Specified build.yaml as input but the file does not contain valid options, ignoring...

The build then proceeds and succeeds. The message is misleading: nothing is wrong with FlutterGen’s configuration, and build.yaml intentionally does not contain FlutterGen options.

Expected behavior

• If FlutterGen configuration is in pubspec.yaml, and there is a build.yaml that does not contain FlutterGen options, FlutterGen should:

  • either not read build.yaml at all, or
  • log at INFO/DEBUG (not SEVERE) that it found no FlutterGen options and is using pubspec.yaml.

• A SEVERE log should be reserved for an actual configuration error (e.g., invalid keys or values in the file that FlutterGen is supposed to read).

Actual behavior

• FlutterGen emits a SEVERE log line whenever build.yaml is present but doesn’t contain FlutterGen options, even though configuration is valid in pubspec.yaml.
• This is noisy in CI and can be mistaken for a real error.

---

Steps to reproduce

1. Create a Flutter package/app.

2. Put FlutterGen configuration in pubspec.yaml (example below).

3. Add a build.yaml at the package root for unrelated builders (e.g., graphql_codegen, go_router_builder), without any FlutterGen section.

4. Run:

   dart run build_runner build --delete-conflicting-outputs

5. Observe the SEVERE message from FlutterGen, even though the build succeeds.

pubspec.yaml (relevant part):

flutter_gen:
  output: lib/gen/
  line_length: 80
  integrations:
    flutter_svg: true

build.yaml (example for other builders only):

targets:
  $default:
    builders:
      graphql_codegen:graphql_codegen:
        options:
          clients: [graphql]

global_options:
  go_router_builder:go_router_builder:
    runs_before:
      - graphql_codegen:graphql_codegen

Log excerpt:

[INFO] Generating build script completed, took 151ms
[INFO] Precompiling build script... completed, took 3.0s
[SEVERE] FlutterGen:
Specified build.yaml as input but the file does not contain valid options, ignoring...
[INFO] Building new asset graph completed, took 902ms
...
[INFO] Succeeded after 13.5s with 208 outputs (1246 actions)

---

Environment

• flutter_gen_runner: 5.11.0
• flutter_gen_core: 5.11.0
• build_runner: 2.4.15
• Dart SDK: 3.8.x
• Flutter: 3.32.x
• OS: macOS 15.6

---

Impact

• Causes false‑positive “errors” in local logs and CI.
• Can trigger CI failure if logs are parsed for error severity.
• Confuses users into chasing a non‑issue.

---

Workarounds (not ideal)

• Add a minimal FlutterGen block to build.yaml just to silence the message:

  targets:
    $default:
      builders:
        flutter_gen_runner:
          options:
            output: lib/gen/

  This defeats the purpose of using pubspec.yaml as the canonical place for FlutterGen config.

• Ignore the message (noisy in CI).

---

Suggested fix

• Detection logic: Only attempt to parse build.yaml for FlutterGen when it contains known FlutterGen keys (e.g., targets.$default.builders.flutter_gen_runner or flutter_gen sections). Otherwise skip quietly.

• Severity: If you still want to log, downgrade to INFO/DEBUG with wording like:

  “FlutterGen: No FlutterGen options in build.yaml; using pubspec.yaml/defaults.”

• Docs note: Clarify precedence and that having a build.yaml for other builders is supported and should not produce a severe error.

---

Additional context

I maintain a build.yaml for other tools (e.g., graphql_codegen, go_router_builder) and keep FlutterGen settings in pubspec.yaml. The configuration is valid, and the build succeeds; only the severity of the log line is problematic.

[TykanN]

I agree with this. +1