Extract file-based app entry point heuristic

[mwiemer-microsoft]

Summary

• Extract the file-based program entry-point classification into a shared internal heuristic
• Preserve existing open-file classification behavior, including avoiding ambiguous top-level-statement parsing when ambiguous entry points are disabled

Validation

• dotnet build src\LanguageServer\Microsoft.CodeAnalysis.LanguageServer\Microsoft.CodeAnalysis.LanguageServer.csproj --no-restore
• dotnet test src\LanguageServer\Microsoft.CodeAnalysis.LanguageServer.UnitTests\Microsoft.CodeAnalysis.LanguageServer.UnitTests.csproj --filter "FullyQualifiedName~FileBasedProgramsEntryPointDiscoveryTests" --no-restore

Microsoft Reviewers: Open in CodeFlow

[Copilot]

Pull request overview

This PR refactors the file-based program “entry point” classification logic in the Language Server by extracting it into a shared internal heuristic, and adds focused unit tests to validate explicit, ambiguous, and non-entry-point outcomes.

Changes:

• Introduces FileBasedProgramEntryPointKind and FileBasedProgramEntryPointHeuristic.GetEntryPointKind(...) to centralize entry-point classification.
• Updates FileBasedProgramsProjectSystem.ClassifyDocumentAsync to use the extracted heuristic while preserving the existing option-gated “ambiguous entry point” behavior.
• Adds a new theory to unit test the heuristic across representative inputs (shebang, #: directives, top-level statements, and non-entry-point cases).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer/FileBasedPrograms/FileBasedProgramsProjectSystem.cs	Extracts entry-point classification into an internal heuristic and rewires document classification to use it.
src/LanguageServer/Microsoft.CodeAnalysis.LanguageServer.UnitTests/MiscellaneousFiles/FileBasedProgramsEntryPointDiscoveryTests.cs	Adds direct unit coverage for the new heuristic’s explicit/ambiguous/none outcomes.