[api_summary] Add expectApiSummaryClean and --write/--check CLI flags

[kevmoo]

Adds a build_verify-style one-liner test helper (expectApiSummaryClean) and companion --write (-w), --check (-c), and --output (-o) CLI flags to package:api_summary (v1.1.0).

• Programmatic Tear-Off (expectApiSummaryClean):
  • Verifies that a package's generated ApiSummary matches its checked-in golden file (api.txt, api.json, or api.yaml).
  • Because all parameters are optional and named (packagePath defaults to Directory.current), it can be passed directly as a tear-off to test():

    import 'package:api_summary/api_summary.dart';
    import 'package:test/scaffolding.dart';
    
    void main() {
      test('api_summary', expectApiSummaryClean);
    }

  • Throws ApiSummaryVerificationException with a compact line diff and copy-pasteable remediation command (dart run api_summary --write) without requiring package:test in api_summary's runtime dependencies.
• CLI Enhancements (bin/api_summary.dart):
  • -w, --write: Writes the summary to the default golden file (api.txt, api.json, or api.yaml) in the package root.
  • -c, --check: Verifies that the existing golden file matches the current public API, exiting with code 1 on mismatch.
  • -o, --output <file>: Writes the summary to a custom file path instead of stdout (relative paths resolve relative to --package-path).
  • Enforces mutual exclusivity between --write, --check, and --output via an exhaustive record switch (exiting with code 64 on invalid combinations or unexpected positional arguments).
• Self-Dogfooding & Tests (test/app_test.dart):
  • Dogfoods expectApiSummaryClean for api.txt, api.json, and api.yaml and pre-compiles bin/api_summary.dart to a kernel .dill in setUpAll (cutting test/app_test.dart execution time from ~105s to ~44s).

[github-actions]

Package publishing

If you have publishing permissions, you can use the links below to publish the changes after merging this PR.

Package	Version	Status	Publish tag (post-merge)
package:api_summary ⭐	1.1.0	ready to publish	api_summary-v1.1.0
package:pubspec_parse	1.6.1	ready to publish	pubspec_parse-v1.6.1
package:test_reflective_loader	0.6.0	ready to publish	test_reflective_loader-v0.6.0

• 18 already published.
• 21 WIP (no publish necessary).

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.

[gemini-code-assist]

Code Review

This pull request introduces golden file verification capabilities to the api_summary package, adding the expectApiSummaryClean function, ApiSummaryFormat enum, and ApiSummaryVerificationException class to support one-liner golden file verification in tests. It also extends the CLI executable with --write (-w), --check (-c), and --output (-o) flags. The review feedback highlights three key issues: a failure to correctly resolve the caller's package directory when api_summary is consumed as a pub dependency with a version suffix, a path resolution discrepancy in the CLI when combining a custom package path with a relative output path, and a regex parsing limitation in resolveCallerPackageDirectory when file paths contain parentheses.

[github-actions]

PR Health

Coverage ⚠️

File	Coverage
pkgs/api_summary/bin/api_summary.dart	💔 Not covered
pkgs/api_summary/lib/api_summary.dart	💚 98 %
pkgs/api_summary/lib/src/verify.dart	💚 92 %

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// Copyright (c) 2026, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

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Package	Change	Current Version	New Version	Needed Version	Looking good?
api_summary	Non-Breaking	1.0.0	1.1.0	1.1.0	✔️

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