Ignore embedded debug format for metadata-only emit by jaredpar · Pull Request #85028 · dotnet/roslyn

jaredpar · 2026-08-25T16:52:52Z

Summary

Metadata-only output cannot have an associated PDB. However, /refonly /debug:embedded synthesized a PDB path and emitted a CodeView debug-directory entry even though no PDB was produced.

This change:

allows EmitMetadataOnly with DebugInformationFormat.Embedded instead of throwing, bringing the public API into alignment with command-line behavior;
suppresses the effective PDB path for metadata-only output, preventing PDB-related debug-directory entries;
preserves the Reproducible entry for deterministic builds; and
adds coverage for both the public emit API and the /refonly /debug:embedded command-line path.

Testing

CompilationEmitTests.EmitMetadataOnly_IgnoreEmbeddedPdb
CommandLineTests.RefOnly_EmbeddedDebugInformation

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azure-pipelines · 2026-08-25T16:53:31Z

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jaredpar · 2026-08-25T23:47:20Z

@dotnet/roslyn-compiler PTAL

azure-pipelines · 2026-08-25T23:47:24Z

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Pull request overview

This pull request adjusts Roslyn’s emit pipeline so metadata-only outputs (reference assemblies) don’t synthesize a PDB path or emit PDB-related debug directory entries when /debug:embedded is requested, aligning EmitMetadataOnly behavior with the command-line /refonly path.

Changes:

Removes the EmitMetadataOnly + DebugInformationFormat.Embedded argument exception so the public emit API no longer throws for this combination.
Clears the effective PDB path during metadata-only serialization to prevent emitting CodeView (and related) debug-directory entries when no PDB exists.
Adds regression tests for both the public emit API and /refonly /debug:embedded command-line behavior.

Show a summary per file

File	Description
src/Compilers/CSharp/Test/Emit/Emit/CompilationEmitTests.cs	Updates the metadata-only embedded-debug test to assert successful emit and validate debug directory contents.
src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs	Adds a `/refonly /debug:embedded` test verifying the debug directory only contains `Reproducible`.
src/Compilers/Core/Portable/Compilation/Compilation.cs	Removes the embedded+metadata-only throw and suppresses the PDB path for metadata-only emit to avoid PDB-related debug directory entries.

Review details

Files reviewed: 3/3 changed files
Comments generated: 2
Review effort level: Lite

+            Assert.Equal(0, csc.Run(outWriter));
+            Assert.Equal("", outWriter.ToString());
+
+            using (var peReader = new PEReader(File.OpenRead(Path.Combine(dir.Path, "a.dll"))))
+            {
+                AssertEx.Equal(
+                    new[] { DebugDirectoryEntryType.Reproducible },
+                    peReader.ReadDebugDirectory().Select(entry => entry.Type));
+            }


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Review details

Files reviewed: 17/17 changed files
Comments generated: 0 new
Review effort level: Lite

jjonescz · 2026-08-28T11:51:47Z

Looks like there are real assert failures that are failing tests in CI.

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Findings: 1

Pre-existing issues (1)

Severity	Finding
	`src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs` — This test verifies the debug directory entries, but it doesn't assert that no PDB is produced on… View comment

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Review tier: Lite
Findings: 1 · 1

New issues introduced by this change (1)

Severity	Finding
	`src/Compilers/CSharp/Test/Emit/Emit/CompilationEmitTests.cs` — `EmitToArray` auto-creates a discrete PDB stream for Debug compilations unless the debug format is…

Pre-existing issues (1)

Severity	Finding
	`src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs` — This test verifies the debug directory entries, but it doesn't assert that no PDB is produced on… View comment

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Review tier: Lite
Findings: 1 · 2

New issues introduced by this change (1)

Severity	Finding
	`src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs` — This change affects the shared command-line emit path (`CommonCompiler`) and thus applies to both…

Pre-existing issues (2)

Severity	Finding
	`src/Compilers/CSharp/Test/Emit/Emit/CompilationEmitTests.cs` — `EmitToArray` auto-creates a discrete PDB stream for Debug compilations unless the debug format is… View comment
	`src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs` — This test verifies the debug directory entries, but it doesn't assert that no PDB is produced on… View comment

Suppressed comments (1)

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs:12068

The new command-line regression test validates the debug directory contents, but it doesn’t assert that no standalone PDB file was produced. Since the underlying issue is specifically “CodeView entry with no PDB”, adding an explicit a.pdb non-existence check would make the test fail for regressions that start writing a PDB again.

            CleanupAllGeneratedFiles(dir.Path);

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azure-pipelines · 2026-09-08T20:48:21Z

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Copilot review overview

🟢 Approval recommended

The behavior change is localized, consistent across API and CLI, and is covered by targeted C# and VB regression tests.

Review tier: Lite
Findings: 1

Pre-existing issues (1)

Severity	Finding
	`src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs` — This test verifies the debug directory entries, but it doesn't assert that no PDB is produced on… View comment

Issues resolved since last review (2)

Severity	Finding
	`src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs` — This change affects the shared command-line emit path (`CommonCompiler`) and thus applies to both… View resolved comment
	`src/Compilers/CSharp/Test/Emit/Emit/CompilationEmitTests.cs` — `EmitToArray` auto-creates a discrete PDB stream for Debug compilations unless the debug format is… View resolved comment

Ignore embedded debug format for metadata-only emit

a8c427b

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jaredpar marked this pull request as ready for review August 25, 2026 23:47

jaredpar requested a review from a team as a code owner August 25, 2026 23:47

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build-analysis Bot mentioned this pull request Aug 26, 2026

[Known Build Error] System.Threading.Tasks.TaskCanceledException #84846

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jjonescz reviewed Aug 26, 2026

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Comment thread src/Compilers/Core/Portable/Compilation/Compilation.cs

Comment thread src/Compilers/Core/Portable/Compilation/Compilation.cs

Remove unused embedded PDB resource

f6a9398

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jaredpar mentioned this pull request Aug 27, 2026

Work around metadata-only PDB emit failures jaredpar/complog#385

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Merge branch 'main' into jaredpar-fix-refonly-embedded-debug

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Copilot AI review requested due to automatic review settings August 31, 2026 17:28

Suppress PDB output for metadata-only emit

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Comment thread src/Compilers/CSharp/Test/Emit/Emit/CompilationEmitTests.cs Outdated

Copilot AI review requested due to automatic review settings August 31, 2026 17:52

Suppress metadata-only PDB work in callers

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Comment thread src/Compilers/Core/Portable/CommandLine/CommonCompiler.cs

jaredpar marked this pull request as draft August 31, 2026 23:24

jaredpar and others added 2 commits August 31, 2026 16:30

Test VB ref-only embedded debug output

a00f734

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Merge branch 'main' into jaredpar-fix-refonly-embedded-debug

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jaredpar marked this pull request as ready for review September 8, 2026 20:48

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jaredpar merged commit a6e73e2 into dotnet:main Sep 10, 2026
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dotnet-policy-service Bot added this to the Next milestone Sep 10, 2026

This was referenced Sep 11, 2026

[release/11.0.1xx] Source code updates from dotnet/roslyn dotnet/dotnet#9250

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[main] Source code updates from dotnet/roslyn dotnet/dotnet#9256

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dotnet-bot mentioned this pull request Sep 11, 2026

[Automated] PRs inserted in VS build main-12211.24 #85259

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dibarbet mentioned this pull request Sep 11, 2026

Update roslyn to 5.12.0-1.26461.1 dotnet/vscode-csharp#9751

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Summary

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