Fix #pragma warning not working with multifile modules (#7942)

* Initial plan

* Fix pragma warning not working with multifile modules

- Check if DiagnosticSink already has a WarningStateTracker before creating new one
- This preserves pragma warning state across __include'd files
- Add regression tests for multifile pragma warnings

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

* Add additional test cases for nested pragma warnings

- Test nested __include scenarios with pragma warning directives
- Verify pragma warnings work correctly with multiple levels of includes

Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: csyonghe <2652293+csyonghe@users.noreply.github.com>
Co-authored-by: Yong He <yonghe@outlook.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/source/slang/slang-preprocessor.cpp b/source/slang/slang-preprocessor.cpp
index b29fa2716..a0e80473d 100644
--- a/source/slang/slang-preprocessor.cpp
+++ b/source/slang/slang-preprocessor.cpp
@@ -4878,9 +4878,14 @@ TokenList preprocessSource(
         desc.contentAssistInfo = &linkage->contentAssistInfo.preprocessorInfo;
     }
 
-    preprocessor::WarningStateTracker* wst =
-        new preprocessor::WarningStateTracker(desc.sourceManager);
-    desc.sink->setSourceWarningStateTracker(wst);
+    // Only create a new WarningStateTracker if the sink doesn't already have one.
+    // This ensures pragma warning states are preserved across included files.
+    if (!desc.sink->getSourceWarningStateTracker())
+    {
+        preprocessor::WarningStateTracker* wst =
+            new preprocessor::WarningStateTracker(desc.sourceManager);
+        desc.sink->setSourceWarningStateTracker(wst);
+    }
 
     return preprocessSource(file, desc, outDetectedLanguage, outLanguageVersion);
 }