Parse dart files with the SDK version from the pubspec

[gmpassos]

Problem

getDartDirectivePackageNames parsed every dart file with parseString's default feature set, FeatureSet.latestLanguageVersion(). Syntax newer than the package's declared SDK constraint was therefore accepted silently, even though the analyzer would reject it in the package it lives in.

Change

checkPackage resolves a FeatureSet from the environment: sdk: lower bound of the pubspec it already parses (truncated to major.minor.0, since a language version has no patch component) and passes it down to getDartDirectivePackageNames:

final featureSet = featureSetForPubspec(pubspec);
...
getDartDirectivePackageNames(file, featureSet: featureSet)

• featureSetForPubspec falls back to FeatureSet.latestLanguageVersion() when there is no SDK lower bound.
• A bare pin (sdk: 3.0.0) works too — Version implements VersionRange with itself as the lower bound.
• Workspace sub-packages get their own feature set, since checkPackage already recurses per sub-package.
• // @dart=x.y overrides still apply: parseString hands the feature set to the scanner as featureSetForOverriding.

Behavior change

A file using syntax newer than its pubspec's SDK lower bound now hits the existing ArgumentError path in getDartDirectivePackageNames, which prints the diagnostic and exits 1. Such code is genuinely invalid under language versioning, but it is a harder failure than before.

Testing

• dart analyze / dart format clean.
• End-to-end against a scratch package containing sealed class: with sdk: ">=2.19.0 <4.0.0" it now reports experiment_not_enabled: This requires the 'sealed-class' language feature to be enabled; with sdk: ^3.0.0 it parses and validates normally.
• dart test: 84 passing. The 4 failures in test/executable_test.dart are pre-existing and reproduce identically on unmodified master (their fixtures need network access for pub get).

🤖 Generated with Claude Code

https://claude.ai/code/session_01JUxxy3wafsbkdCCRqmZEDd