[alan-agius4]

Summary

• Forward warnings from compilationInstance.initialize(...) into the formatted warnings output.
• Run syntactic and option diagnostics (DiagnosticModes.All & ~DiagnosticModes.Semantic) when useTypeChecking is false.
• Run diagnoseFiles even when stylesheetErrors.length > 0 so AotCompilation drains affectedFiles into diagnosticCache (preventing dropped template diagnostics on subsequent watch rebuilds), and ensure diagnosePromise cannot cause an unhandled rejection.
• Pass 'css' as the language for inline <style> tags in external .html templates when calling stylesheetBundler.bundleInline(...).
• Only clear previous file references for a target file right before buildState.addFileReferences(...) when stylesheet bundling succeeds on incremental builds, preserving existing transitive references if bundling fails.

[gemini-code-assist]

Code Review

This pull request refactors the Angular library compilation pipeline to improve diagnostic handling, file reference tracking, and caching. Key changes include passing the 'css' language option to inline style bundling for external HTML templates, refining file reference management to preserve references during stylesheet bundling failures, extracting cache updates into a helper function, and wrapping diagnostic steps in try-catch blocks to handle errors gracefully. Comprehensive unit and behavior tests have been added to verify these changes. No review comments were provided, so there is no feedback to address.