File-based apps: Add support for #:ref directive

[RikkiGibson]

• Adds a classification test
• Adds a completion provider

Microsoft Reviewers: Open in CodeFlow

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[Copilot]

Pull request overview

This PR adds IDE support for the #:ref directive in C# file-based programs by introducing a dedicated completion provider, adding syntactic classification coverage, and wiring up the related user-facing resource strings (including localized .xlf entries).

Changes:

• Add RefAppDirectiveCompletionProvider to offer #:ref directive completion and .cs path completion for file-based programs.
• Extend completion provider ordering tests and add directive-specific completion tests for #:ref.
• Add syntactic classification coverage for #:ref and add new resource strings + localized .xlf entries.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hant.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.zh-Hans.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.tr.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ru.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pt-BR.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.pl.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ko.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.ja.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.it.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.fr.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.es.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.de.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/xlf/CSharpFeaturesResources.cs.xlf	Adds new localized string entries for the #:ref directive description and placeholder.
src/Features/CSharp/Portable/CSharpFeaturesResources.resx	Adds the base resource strings for #:ref directive placeholder and description.
src/Features/CSharp/Portable/Completion/CompletionProviders/LastBuiltInCompletionProvider.cs	Updates completion provider ordering so the built-in marker comes after the new RefAppDirectiveCompletionProvider.
src/Features/CSharp/Portable/Completion/CompletionProviders/FileBasedPrograms/RefAppDirectiveCompletionProvider.cs	Introduces the new completion provider for the #:ref directive and .cs file path completion.
src/EditorFeatures/CSharpTest/Completion/CompletionProviders/CompletionProviderOrderTests.cs	Updates expected built-in completion provider order to include the new provider.
src/EditorFeatures/CSharpTest/Completion/CompletionProviders/AppDirectiveCompletionProviderTests.cs	Adds completion tests specifically for #:ref path recommendations and .cs-only filtering.
src/EditorFeatures/CSharpTest/Classification/SyntacticClassifierTests_FileBasedApps.cs	Adds a syntactic classification test covering #:ref.

Suppressed comments (1)

src/Features/CSharp/Portable/CSharpFeaturesResources.resx:638

• Adds_a_file_based_app_reference currently says "References another file-based app as a library." The #:ref spec describes this as referencing another .cs file as a separate (virtual) project reference, and the referenced file can still default to OutputType=Exe unless overridden. Consider rewording this string to describe a project reference to another .cs file-based program instead of implying it’s always a library.

  <data name="Adds_a_file_based_app_reference" xml:space="preserve">
    <value>References another file-based app as a library.</value>
  </data>

[RikkiGibson]

CI analysis for build 1540027:

• Test_Windows_CoreClr_RuntimeAsync_Debug failed CommandLineTests.TestSuppression_CompilerSyntaxParseError_SuppressWarningCaughtDuringParsingStage(skipAnalyzers: false) because pool validation found an ArrayBuilder<ReadOnlyMemory<char>> allocated by MetadataHelpers was not returned.
• The log does not report an underlying exception from the compiler/analyzer path; the only surfaced exception is the pool validator's failure after the test. Therefore we cannot yet identify what interrupted cleanup or claim that the broad, closed pool-leak KBE [Known Build Error] Pool leak detected #83972 covers this instance.
• Test_Windows_CoreClr_IOperation_Debug and Test_Windows_CoreClr_Debug dead-lettered in Helix with artificial exit code -1, so those are infrastructure failures.
• The immediately preceding build passed at the same merge SHA.

Retrying roslyn-CI and watching for recurrence of the pool leak. If it recurs, we should capture the repeated evidence and file a specific Known Build Error issue rather than matching the generic pool-leak issue.

[RikkiGibson]

/azp run roslyn-CI

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