fix(lsp): use regex for pub workspace detection instead of YAML parsing

[khensunny]

Replace full YAML parsing with simple pattern matching for detecting
pub workspace members and roots. The YAML parser fails silently on
complex pubspec files (e.g., containing generate:dart syntax),
causing workspace root detection to fail and multiple LSP servers
to spawn.

Also fix iterate_parents skipping the immediate parent directory
when searching for workspace root.

Patterns match VS Code Dart extension behavior.

Note

AI was used in the creation of this work

Closes: #515

[Copilot]

Pull request overview

This PR fixes workspace root detection in the LSP by replacing full YAML parsing with simple regex-based pattern matching for detecting pub workspace members and roots. The YAML parser was failing silently on complex pubspec files (e.g., those containing generate:dart syntax), causing workspace root detection to fail and multiple LSP servers to spawn.

Changes:

• Replaced YAML parsing with regex pattern matching for workspace detection, matching VS Code Dart extension behavior
• Fixed iterate_parents skipping the immediate parent directory during workspace root search

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[khensunny]

this is the pubspec.yaml section that made the yaml parser fail:

// melos configure
melos:
// ...
    generate:
      steps:
        - generate:dart
        - generate:flutter
      description: Build all generated files for Dart & Flutter packages.

[sidlatau]

Thanks, @khensunny!