Canonicalize SourceRoot paths in MapSourceRoots #82123

Copilot · 2026-01-23T09:34:58Z

All changes complete and tested. CI formatting issues resolved.

Original prompt

This section details on the original issue you should resolve

<issue_title>Canonicalize SourceRoot paths before returning from InitializeSourceRootMappedPaths</issue_title>
<issue_description>While digging into dotnet/sdk#52614 I found that SourceRoot items are not canonicalized - so items that users (or other MSBuild Logic) add may have relative path portions in them. If those portions are not canonicalized, then path comparisons that occur later on in the build (e.g. for applying PathMaps to embedded source items, and file paths in PDBs) may not compare as expected. This can lead to un-mapped paths in PDBs and other build artifacts.

The InitializeSourceRootMappedPaths target is the documented extension point for anyone that needs to consume SourceRoot items, so it is a logical place to do this canonicalization. We should sanitize the SourceRoot items here so that we don't have to sanitize them N times downstream.</issue_description>

Comments on the Issue (you are @copilot in this section)

Fixes Canonicalize SourceRoot paths before returning from InitializeSourceRootMappedPaths #82112

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

- Added path canonicalization logic in MapSourceRoots.Execute() - Canonicalizes both ItemSpec and ContainingRoot metadata - Only canonicalizes rooted paths with relative components (.. or /.) - Preserves trailing directory separators - Added comprehensive tests for canonicalization behavior Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

- Extract duplication into CanonicalizePathPreservingTrailingSeparator helper - Remove redundant length check - Fix false positive detection for .. by checking path segment boundaries - Also fix false positive for /. by checking if it's a single dot Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

jjonescz

@copilot

src/Compilers/Core/MSBuildTaskTests/MapSourceRootTests.cs

src/Compilers/Core/MSBuildTask/MapSourceRoots.cs

- Simplify by removing ContainsRelativePathComponents method - Normalize all rooted paths unconditionally - Add CanonicalizeRelativePathPreservingTrailingSeparator for NestedRoot - Change PathCanonicalization_Deterministic to use CombinatorialData - Add test for ContainingRoot and NestedRoot canonicalization Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

- Improve comment explaining canonicalization for rooted paths - Use StringComparison.Ordinal for StartsWith check - Use verbatim string for dummy root path clarity Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot · 2026-01-23T10:54:22Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

bcnvsblobprodcus378.vsblob.vsassets.io
- Triggering command: /usr/share/dotnet/dotnet dotnet build src/Compilers/Core/MSBuildTask/MSBuild/Microsoft.Build.Tasks.CodeAnalysis.csproj grep -l WorkItem entationCommentTests.cs ndor/bin/grep WorkItem mentsTests.cs /usr/local/sbin/WorkItem grep -l WorkItem orDocumentationCommentTests.cs /home/REDACTED/.cargo/bin/grep WorkItem cs ndor/bin/grep grep (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot · 2026-01-23T11:01:09Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

bcnvsblobprodcus378.vsblob.vsassets.io
- Triggering command: /usr/share/dotnet/dotnet dotnet build src/Compilers/Core/MSBuildTaskTests/Microsoft.Build.Tasks.CodeAnalysis.UnitTests.csproj (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

src/Compilers/Core/MSBuildTask/MapSourceRoots.cs

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot · 2026-01-23T12:06:00Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

bcnvsblobprodcus378.vsblob.vsassets.io
- Triggering command: /usr/share/dotnet/dotnet dotnet build src/Compilers/Core/MSBuildTask/MSBuild/Microsoft.Build.Tasks.CodeAnalysis.csproj (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot · 2026-01-23T13:13:40Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

bcnvsblobprodcus378.vsblob.vsassets.io
- Triggering command: /usr/share/dotnet/dotnet dotnet build src/Compilers/Core/MSBuildTaskTests/Microsoft.Build.Tasks.CodeAnalysis.UnitTests.csproj (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

baronfel · 2026-01-23T15:22:34Z

@jjonescz the copilot implementation seems to be pretty gung-ho about not absolutizing relative paths passed in - but I think absolutizing paths is fine here. Better this explicit expansion than an implicit one at hand wave some point later on in the build. Do you have any thoughts?

Initial plan

fd1d189

Copilot AI assigned Copilot and jjonescz Jan 23, 2026

Copilot started work on behalf of jjonescz January 23, 2026 09:36 View session

Copilot AI and others added 3 commits January 23, 2026 09:40

Add SourceRoot path canonicalization to MapSourceRoots task

e103ccb

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Canonicalize SourceRoot paths in InitializeSourceRootMappedPaths~~ Canonicalize SourceRoot paths with relative components in MapSourceRoots Jan 23, 2026

Copilot AI requested a review from jjonescz January 23, 2026 10:01

Copilot finished work on behalf of jjonescz January 23, 2026 10:01

jjonescz reviewed Jan 23, 2026

View reviewed changes

Copilot started work on behalf of jjonescz January 23, 2026 10:42 View session

Copilot AI and others added 2 commits January 23, 2026 10:52

Address code review suggestions

7f39358

- Improve comment explaining canonicalization for rooted paths - Use StringComparison.Ordinal for StartsWith check - Use verbatim string for dummy root path clarity Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot AI changed the title ~~Canonicalize SourceRoot paths with relative components in MapSourceRoots~~ Canonicalize SourceRoot paths in MapSourceRoots Jan 23, 2026

Copilot AI requested a review from jjonescz January 23, 2026 10:54

Copilot finished work on behalf of jjonescz January 23, 2026 10:54

Copilot started work on behalf of jjonescz January 23, 2026 10:56 View session

Add WorkItem attribute to new tests referencing issue 82112

c5a8500

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot finished work on behalf of jjonescz January 23, 2026 11:01

jjonescz reviewed Jan 23, 2026

View reviewed changes

src/Compilers/Core/MSBuildTask/MapSourceRoots.cs Outdated Show resolved Hide resolved

Copilot started work on behalf of jjonescz January 23, 2026 12:01 View session

Fix trailing whitespace to resolve IDE0055 formatting errors

bc4b973

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot AI requested a review from jjonescz January 23, 2026 12:06

Copilot finished work on behalf of jjonescz January 23, 2026 12:06

Copilot started work on behalf of jjonescz January 23, 2026 13:08 View session

Fix trailing whitespace in MapSourceRootTests.cs

bf0d614

Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

Copilot finished work on behalf of jjonescz January 23, 2026 13:13

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Canonicalize SourceRoot paths in MapSourceRoots #82123

Canonicalize SourceRoot paths in MapSourceRoots #82123

Copilot AI commented Jan 23, 2026 •

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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baronfel commented Jan 23, 2026

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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Copilot AI commented Jan 23, 2026

I tried to connect to the following addresses, but was blocked by firewall rules:

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baronfel commented Jan 23, 2026

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Copilot AI commented Jan 23, 2026 •

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