[infra] Add license checker to ci script

[dcharkes]

This enables running (and fixing automatically) locally.

The ecosystem check is skipping build directories: https://github.com/dart-lang/ecosystem/blob/main/pkgs/firehose/lib/src/health/license.dart This caused the CI to miss: #3113

Also, we should add license checks to non-dart files (follow up PR).

So, lets run this on the CI here on GitHub as well.

[goderbauer]

So why is the license header check that we have on github not enough to catch this and we need to implement our own thing?

[goderbauer]

Also, Windows is unhappy.

[dcharkes]

So why is the license header check that we have on github not enough to catch this and we need to implement our own thing?

I can't run that check locally. I can't tell contributors to run that check locally. It doesn't work in any build/ dirs. And it can only do Dart files (which this PR doesn't fix yet).

If you have any ideas on how to un github-i-fy the dart-lang/ecosystem checks so we can run them easily with a script locally, I'd be happy for that as an alternative.

[goderbauer]

Okay, but why didn't that check catch the missing license headers? Is it broken? Are we running the license checker now twice on CI (this one and the one from the github actions) with different sources of truth of what the license should look like?

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
hooks	None	1.0.1	1.0.2-wip	1.0.2-wip	✔️

This check can be disabled by tagging the PR with skip-breaking-check.

Changelog Entry ✔️

Package	Changed Files

Changes to files need to be accounted for in their respective changelogs.

This check can be disabled by tagging the PR with skip-changelog-check.

License Headers ✔️

// 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.

Files
no missing headers

All source files should start with a license header.

Unrelated files missing license headers

Files
pkgs/jni/test/debug_release_test.dart
pkgs/objective_c/example/command_line/lib/main.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

This check can be disabled by tagging the PR with skip-license-check.

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbol	Leaking sources

This check can be disabled by tagging the PR with skip-leaking-check.

[dcharkes]

Okay, but why didn't that check catch the missing license headers? Is it broken?

I believe it blanket ignores build/ directories. Glancing at the source code it only supports glob, so it cannot ignore only Flutter build directories.

Are we running the license checker now twice on CI (this one and the one from the github actions) with different sources of truth of what the license should look like?

Should we disable the ecosystem one? As I will add non-Dart license header checks to this one.

[coveralls]

coverage: 78.178%. remained the same
when pulling f146809 on infra-licence-checker
into 938b861 on main.