Fix source generator diagnostics to support #pragma warning disable

[eiriktsarpalis]

Summary

Source generator diagnostics emitted by incremental generators in dotnet/runtime can now be suppressed using #pragma warning disable inline directives.

Fixes #92509

Problem

Incremental source generators that store diagnostic locations in equatable intermediate representations "trim" the Location to avoid holding references to the Compilation object. The standard workaround — Location.Create(filePath, textSpan, linePositionSpan) — creates an ExternalFileLocation (LocationKind.ExternalFile) which bypasses Roslyn's pragma suppression checks. Only SourceLocation (LocationKind.SourceFile) instances, created via Location.Create(SyntaxTree, TextSpan), are checked against the SyntaxTree's pragma directive table.

This is the issue described in dotnet/roslyn#68291.

Solution

Following the technique first applied in eiriktsarpalis/PolyType#401, split each affected generator's RegisterSourceOutput pipeline into two separate pipelines:

1. Source generation pipeline — Fully incremental. Uses Select to extract just the equatable model (which contains no Location/SyntaxTree references), deduplicates by model equality, only re-fires on structural changes.
2. Diagnostic pipeline — Reports raw Diagnostic objects that preserve the original SourceLocation (LocationKind.SourceFile) from the syntax tree. This enables Roslyn to check the SyntaxTree's pragma directive table for #pragma warning disable directives.

Parsers now create Diagnostic.Create(descriptor, location, ...) directly instead of wrapping in DiagnosticInfo.Create(...) which trimmed the location. Since ImmutableArray<Diagnostic> does not have value equality, the diagnostic pipeline fires more frequently but the work is trivially cheap (just iterating and reporting).

[Copilot]

Pull request overview

Enables Roslyn pragma-based suppression (#pragma warning disable) for diagnostics emitted by several incremental source generators by separating source emission from diagnostic emission and recreating diagnostics with SourceFile locations recovered from the current Compilation.

Changes:

• Split generator pipelines into (1) fully-incremental source generation and (2) diagnostics combined with CompilationProvider for pragma-suppressible locations.
• Add DiagnosticInfo.CreateDiagnostic(Compilation) (and Regex-specific equivalent) to rebuild Location as LocationKind.SourceFile.
• Update Json source generator incremental test commentary to reflect the new diagnostics pipeline behavior.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.cs	Adds a diagnostics-only pipeline and recreates diagnostics with SourceFile locations.
src/libraries/System.Text.Json/tests/System.Text.Json.SourceGeneration.Unit.Tests/JsonSourceGeneratorIncrementalTests.cs	Adjusts incremental-model encapsulation test commentary given diagnostics now reference SyntaxTree.
src/libraries/System.Text.Json/gen/JsonSourceGenerator.Roslyn4.0.cs	Splits Json SG into separate source + diagnostics pipelines; diagnostics now created with compilation context.
src/libraries/Microsoft.Extensions.Logging.Abstractions/gen/LoggerMessageGenerator.Roslyn4.0.cs	Splits LoggerMessage SG pipelines and preserves diagnostic deduping while making locations pragma-suppressible.
src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs	Splits binder SG pipelines and reports diagnostics using compilation-backed SourceFile locations.
src/libraries/Common/src/SourceGenerators/DiagnosticInfo.cs	Adds CreateDiagnostic(Compilation) to recreate pragma-suppressible SourceFile locations from trimmed locations.

[Copilot]

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs:66

• The catch block rethrows with throw ex;, which resets the exception stack trace. Use throw; (or remove the catch entirely) to preserve the original call stack for diagnosing generator failures.

                    catch (Exception ex)
                    {
                        throw ex;
                    }

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs:66

• The catch (Exception ex) { throw ex; } pattern resets the original stack trace. If the intent is just to propagate, use throw; (or remove the try/catch entirely) so failures in the generator preserve useful call stacks.

                    catch (Exception ex)
                    {
                        throw ex;
                    }

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs:66

• Avoid throw ex; here; it resets the original stack trace and makes failures harder to diagnose. Use throw; to preserve the stack trace, or remove the try/catch entirely if it's only rethrowing.

                    catch (Exception ex)
                    {
                        throw ex;
                    }

[Copilot]

Pull request overview

Copilot reviewed 17 out of 17 changed files in this pull request and generated 2 comments.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs:66

• The catch (Exception ex) { throw ex; } rethrow resets the original stack trace and also adds no value here. Use throw; to preserve the stack (or remove the try/catch entirely and let the exception bubble).

                    catch (Exception ex)
                    {
                        throw ex;
                    }

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[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs:66

• The catch (Exception ex) { throw ex; } pattern resets the original stack trace, making failures much harder to diagnose. Use throw; to preserve the stack trace (or remove the try/catch if it isn't adding handling).

                    catch (Exception ex)
                    {
                        throw ex;
                    }

---

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[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (1)

src/libraries/Microsoft.Extensions.Configuration.Binder/gen/ConfigurationBindingGenerator.cs:66

• throw ex; resets the stack trace and makes failures harder to diagnose. Either remove this try/catch (letting the original exception propagate) or use a bare throw; to preserve the original stack trace.

                    catch (Exception ex)
                    {
                        throw ex;
                    }

---

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[Copilot]

Pull request overview

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

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[ericstj]

Do we need to do anything in the interop generators?

[ericstj]

Can you please remove this file from the other generators' targets files?

[ericstj]

Should this include message as well?

[ericstj]

Consider some additional test cases, not sure how much our generator implementation would actually be exposed to these differences of it's more roslyn but sharing some thoughts:

1. No pragma does not supporess.
2. Multiple diagnostics with only some suppressed.
3. Pragma suppress/restore in same file, but outside the reported code span. Perhaps all around it, so it would capture if we somehow got the span line info off-by-1.

[ericstj]

Overall looks good and surprisingly minimal. Feedback is straightforward fix or non-blocking.