Don't log named pipe connection failures as errors in BuildServerConnection by Copilot · Pull Request #82609 · dotnet/roslyn

Copilot · 2026-03-03T17:39:21Z

When connecting to the compiler server fails due to a timeout, pipe ownership mismatch, or other exception, the previous LogException/LogError calls emitted messages prefixed with "Error Error:" or "Error:". This matches the canonical error pattern that MSBuild's Exec task detects in process output, causing it to surface a build error — even though these are transient, recoverable conditions where the compiler falls back gracefully to the command-line tool.

Change

In BuildServerConnection.cs, replace LogException/LogError with plain Log for all three recoverable failure paths in TryConnectToServerAsync. Key diagnostic info (exception type + message) is retained; only the "Error:" prefix is dropped.

- logger.LogException(e, $"Connecting to server timed out after {timeoutMs} ms");
+ logger.Log($"Connecting to server timed out after {timeoutMs} ms: '{e.GetType().Name}' '{e.Message}'");

- logger.LogError("Owner of named pipe is incorrect");
+ logger.Log("Owner of named pipe is incorrect");

- logger.LogException(e, "Exception while connecting to process");
+ logger.Log($"Exception while connecting to process: '{e.GetType().Name}' '{e.Message}'");

LogException/LogError are appropriate for unexpected failures. These connection failures are all handled, recoverable conditions — logging them as errors was misleading.

Original prompt

This section details on the original issue you should resolve

<issue_title>Error Error: 'IOException' 'The semaphore timeout period has expired reported but not really an issue</issue_title>
<issue_description>10.0.103:

During building with Visual Studio 2026 18.3.0 we encounter the following:

EXEC(0,0): Error Error: 'IOException' 'The semaphore timeout period has expired.

It appears that this error is reported, but the build is not failing as a retry is done, but as the error is reported as a canonical error format the exec msbuild task https://learn.microsoft.com/en-us/visualstudio/msbuild/exec-task?view=visualstudio reports an error and stops.

But as this is not really an error as dotnet build is not stopping can the following line be adapted that, it does not report an canonical error

https://github.com/dotnet/roslyn/blob/main/src/Compilers/Shared/BuildServerConnection.cs#L415

</issue_description>

Comments on the Issue (you are @copilot in this section)
@jjonescz > the exec msbuild task https://learn.microsoft.com/en-us/visualstudio/msbuild/exec-task?view=visualstudio reports an error and stops.
I'm not sure what do you mean by this. Where exactly is this Exec task being used? There shouldn't be any Exec task used during normal dotnet build when invoking the C# compiler.</comment_new>

Fixes Error Error: 'IOException' 'The semaphore timeout period has expired reported but not really an issue #82583

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

When a named pipe connection times out (IOException/TimeoutException), the previous LogException call generated "Error Error: 'IOException' 'The semaphore timeout period has expired.'" which matches a canonical error format, causing MSBuild's Exec task to treat it as a build error. Since connection timeout is a recoverable/transient condition (the caller retries or falls back to command-line), change to a plain logger.Log call that preserves the diagnostic info without the "Error:" prefix. Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

jjonescz

@copilot

…nection.cs Same issue: pipe ownership failure and general connect exceptions are also recoverable (both return null → fallback to CLI compiler), so they should not be logged with an "Error:" prefix that could trigger MSBuild's canonical error detection. Co-authored-by: jjonescz <3669664+jjonescz@users.noreply.github.com>

RikkiGibson · 2026-03-04T17:24:17Z

                {
                    pipeStream.Dispose();
-                    logger.LogError("Owner of named pipe is incorrect");
+                    logger.Log("Owner of named pipe is incorrect");


Not blocking: Why not log this as an error? It feels like getting in this situation, requires a more specific "step" to get things wrong. i.e. the wrong user opening a named pipe that happens to have the same name, or similar, which we don't really expect to happen accidentally.

I guess, but we will still fallback to in-process csc invocation, so I think it still makes sense to not fail an Exec task for this, just like we wouldn't fail dotnet build.

* upstream/main: (56 commits) [main] Source code updates from dotnet/dotnet (dotnet#82655) Update insert.yml to use roslyn-tools for insertions (dotnet#82615) Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2921538 Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2921538 Reduce allocations during source text diffing (dotnet#82462) Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2920904 Localized file check-in by OneLocBuild Task: Build definition ID 327: Build ID 2920904 Revert "Throw NotImplementedException when a build errorId is not supported" (dotnet#82638) [main] Source code updates from dotnet/dotnet (dotnet#82623) Revert System.ValueTuple version update (dotnet#82639) Pack enum values Track non-blocking PROTOTYPE comments for `Unions` feature in an issue (dotnet#82637) Update the build system errors instructions for Visual Studio 2026 Don't log named pipe connection failures as errors in BuildServerConnection (dotnet#82609) Fix resx source generator for less common resx metadata and locations (dotnet#81994) Disallow `ref` modifier for a union declaration (dotnet#82632) Add IFSharpInlineHintsService2 for displayAllOverride support (dotnet#82629) Report errors for union members that are not permitted (dotnet#82626) Check language version for union matching and conversions (dotnet#82617) [main] Update dependencies from dotnet/arcade (dotnet#82618) ...

Initial plan

4d1dcbb

Copilot AI assigned Copilot and jjonescz Mar 3, 2026

Copilot started work on behalf of jjonescz March 3, 2026 17:39 View session

Copilot AI changed the title ~~[WIP] Fix IOException reporting during Visual Studio build~~ Don't log named pipe connection timeout as an error Mar 3, 2026

Copilot finished work on behalf of jjonescz March 3, 2026 17:47

jjonescz reviewed Mar 3, 2026

View reviewed changes

Comment thread src/Compilers/Shared/BuildServerConnection.cs

Comment thread src/Compilers/Shared/BuildServerConnection.cs Outdated

Comment thread src/Compilers/Shared/BuildServerConnection.cs Outdated

Copilot started work on behalf of jjonescz March 3, 2026 17:52 View session

Copilot AI changed the title ~~Don't log named pipe connection timeout as an error~~ Don't log named pipe connection failures as errors in BuildServerConnection Mar 3, 2026

Copilot finished work on behalf of jjonescz March 3, 2026 17:56

jjonescz approved these changes Mar 3, 2026

View reviewed changes

jjonescz requested a review from jaredpar March 3, 2026 18:03

jjonescz marked this pull request as ready for review March 3, 2026 22:47

jjonescz requested a review from a team as a code owner March 3, 2026 22:47

jaredpar approved these changes Mar 4, 2026

View reviewed changes

jjonescz requested a review from a team March 4, 2026 16:56

RikkiGibson approved these changes Mar 4, 2026

View reviewed changes

jjonescz merged commit c4b4ee0 into main Mar 5, 2026
24 checks passed

jjonescz deleted the copilot/fix-ioexception-reporting branch March 5, 2026 00:42

dotnet-policy-service Bot added this to the Next milestone Mar 5, 2026

This was referenced Mar 5, 2026

[release/11.0.1xx-preview2] Source code updates from dotnet/roslyn dotnet/dotnet#5237

Merged

[release/10.0.3xx] Source code updates from dotnet/roslyn dotnet/dotnet#5236

Merged

[main] Source code updates from dotnet/roslyn dotnet/dotnet#5266

Merged

This was referenced Mar 10, 2026

[Automated] PRs inserted in VS build main-11609.20 #82668

Closed

[Automated] PRs inserted in VS build feature.debugger.wix5-11613.132 #82758

Closed

jjonescz modified the milestones: Next, 18.6 Mar 31, 2026

Copilot AI mentioned this pull request Jun 10, 2026

Consolidate compiler-server exception logging and treat recoverable pipe failures as non-fatal #84076

Open

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Don't log named pipe connection failures as errors in BuildServerConnection#82609

Don't log named pipe connection failures as errors in BuildServerConnection#82609
jjonescz merged 3 commits into
mainfrom
copilot/fix-ioexception-reporting

Copilot AI commented Mar 3, 2026 •

edited

Loading

Uh oh!

jjonescz left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

RikkiGibson Mar 4, 2026

Uh oh!

jjonescz Mar 4, 2026

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Conversation

Copilot AI commented Mar 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Change

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

Uh oh!

jjonescz left a comment

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

RikkiGibson Mar 4, 2026

Choose a reason for hiding this comment

Uh oh!

jjonescz Mar 4, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Copilot AI commented Mar 3, 2026 •

edited

Loading