[native_assets_builder] Consume the new .dart_tool/package_graph.json

[dcharkes]

Closes: #1968

Our current workflow with rolling into Flutter tools requires the Dart SDK constraint to be a stable Dart release. This means the tests are also run against a stable Dart release. So keep the fallback behavior. (The JSON structure that we use is identical.)

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?

Changelog Entry ✔️

Package	Changed Files

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

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 symbols

License Headers ✔️

// Copyright (c) 2025, 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/lib/src/third_party/generated_bindings.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 87.429% (-0.001%) from 87.43%
when pulling 3e855ba on package-graph
into ae32a51 on main.

[sigurdm]

FYI: The json is not really identical.

For the root package (deps --json)['dependencies'] wil include the dev_dependencies, while (package_graph.json)['dependencies'] only includes the non-dev dependencies.

[dcharkes]

Users should not be using dev-dependencies in their hooks, so that's perfect. 👍