Added a message of enabled logs, and their paths. by AlesProkop · Pull Request #13577 · dotnet/msbuild

AlesProkop · 2026-04-20T11:25:41Z

Context

There was no clear message in the logs when using either the /bl or the /fl flag that would indicate the location of the files that are being created by these logs. Also, there was no consistent way of telling which logs were enabled.

Changes Made

LoggingServiceLogMethods.cs

Added a method LogLoggersUsed(bool fileNames) which lists the names of all enabled logs in a diagnostic verbosity. Added new EventArgs which registers every enabled logger with information. This is then used for logging clickable links of paths that were created by loggers.

LoggerRegisteredEventArgs.cs

New EventArgs used for registering enabled loggers. It cointains infromation about the logger, such as the name of the logger, verbosity on which the logger operates on, file paths to files created by the logger and possible additional output file paths.

ParallelConsoleLogger.cs

Added handling of the LoggerRegisteredEventArgs.

TerminalLogger.cs

Added handling of the LoggerRegisteredEventArgs.

FileLogger.cs

Added a way to read the path to the file created by the filelogger, similarly to how binlog operates.

Testing

Added unit tests to LoggingServicesLogMethod_Tests.cs.

Examples

BinaryLogger, FileLogger, ConsoleLogger

In the console log, we have clickable links:

In the file log, we have

Done Building Project "D:\testproj\testproj.csproj" (default targets).

BinaryLogger: D:\msbuild\msbuild.binlog
FileLogger: D:\msbuild\msbuild.log

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:09.31

Currently, the BinLogger logs its path in its own way but we can see the enabled logs (this will be the same if we enable higher verbosity in all of the logs.)

Enabled logs: BinaryLogger, CentralForwardingLogger, CentralForwardingLogger, ConsoleLogger, FileLogger, InternalTelemetryConsumingLogger, InternalTelemetryForwardingLogger

Then

BinaryLogger, FileLogger, TerminalLogger

In the terminal log, `/tlp:summary` has to be enabled, otherwise, it will not show (this is consistent with how other messages are handled in the TerminalLogger)

AlesProkop · 2026-04-20T11:28:04Z

@dotnet-policy-service agree company="Microsoft"

Copilot

Pull request overview

This PR improves MSBuild’s user-facing logging by surfacing which loggers are enabled (e.g., /bl, /fl) and where their output files are being written, addressing confusion called out in #12261.

Changes:

Introduces LoggerRegisteredEventArgs to publish information about enabled loggers (name/verbosity/output paths).
Adds IFileOutputLogger and updates BinaryLogger/FileLogger to expose their output file paths.
Updates TerminalLogger/ParallelConsoleLogger to collect these events and print output paths at build end; adds new localized resource strings and unit tests.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated 14 comments.

Show a summary per file

File	Description
src/Framework/LoggerRegisteredEventArgs.cs	New Framework event args type used to report enabled logger details
src/Build/BackEnd/Components/Logging/LoggingServiceLogMethods.cs	Emits “enabled logs” message + logger registration events during build start
src/Build/Logging/IFileOutputLogger.cs	New internal interface for loggers that produce a primary output file
src/Build/Logging/FileLogger.cs	Implements `IFileOutputLogger` to expose the log file path
src/Build/Logging/BinaryLogger/BinaryLogger.cs	Implements `IFileOutputLogger` to expose the binlog path
src/Build/Logging/TerminalLogger/TerminalLogger.cs	Captures logger-registration events and prints clickable paths in summary
src/Build/Logging/ParallelLogger/ParallelConsoleLogger.cs	Captures logger-registration events and prints paths in summary
src/Build/Resources/Strings.resx	Adds new resource strings for enabled logs / output file paths
src/Build/Resources/xlf/Strings.*.xlf	Adds corresponding localization entries (state=new)
src/Build/Microsoft.Build.csproj	Includes the new `IFileOutputLogger.cs` compile item
src/Build.UnitTests/BackEnd/LoggingServicesLogMethod_Tests.cs	Adds unit tests for enabled log names and file path reporting

JanProvaznik · 2026-04-28T11:50:20Z

@AlesProkop can you add to the description screenshots/log examples how it looks like with various configs?

I'm interersted in the matrix: (console / terminallogger) x verbosity x (/bl or /fl)

AlesProkop · 2026-04-28T12:55:56Z

@AlesProkop can you add to the description screenshots/log examples how it looks like with various configs?

I'm interersted in the matrix: (console / terminallogger) x verbosity x (/bl or /fl)

@JanProvaznik
Added some examples.

baronfel · 2026-05-08T16:58:08Z

+{
+    internal interface IFileOutputLogger
+    {
+        System.Collections.Generic.IReadOnlyList<string> OutputFilePaths { get; }


This needs documentation/scoping - it'd be entirely reasonable for a logger author to think that this represented the per-project-build primary outputs, so we need comments or naming to clarify the intent/scope of this member.

I wonder if this should be more of a generic string "summary message". For file loggers it makes sense to specify paths, but for example in the once-common path of -flp1:ErrorsOnly;LogFile=build.err -flp2:WarningsOnly;LogFile=build.wrn -flp3:Verbosity=normal;LogFile=build.log the loggers could emit summaries like

Error log written to build.err Warning log written to build.wrn Log at "normal" verbosity written to build.log

?

I'm not sure we actually need that, though.

I added documentation for now. If you think the more generic summary message is worth pursuing in this PR, I will implement it.

@baronfel can you share your opinion whether we would like to have a more generic summary controlled by the logger?

This is an internal interface so I think this is fine for now. If it were public we'd have to think more about what the external surface area would be.

rainersigwald

Overall I like the approach.

rainersigwald · 2026-05-08T17:15:30Z

+{
+    internal interface IFileOutputLogger
+    {
+        System.Collections.Generic.IReadOnlyList<string> OutputFilePaths { get; }


I wonder if this should be more of a generic string "summary message". For file loggers it makes sense to specify paths, but for example in the once-common path of -flp1:ErrorsOnly;LogFile=build.err -flp2:WarningsOnly;LogFile=build.wrn -flp3:Verbosity=normal;LogFile=build.log the loggers could emit summaries like

Error log written to build.err Warning log written to build.wrn Log at "normal" verbosity written to build.log

?

I'm not sure we actually need that, though.

rainersigwald · 2026-05-08T20:50:02Z

+                            CultureInfo.CurrentCulture.TextInfo.ListSeparator + " ",
+                            logger.OutputFilePaths.Select(outputPath => $"{AnsiCodes.LinkPrefix}{new Uri(outputPath).AbsoluteUri}{AnsiCodes.LinkInfix}{outputPath}{AnsiCodes.LinkSuffix}"));
+
+                        Terminal.WriteLine(ResourceUtilities.FormatResourceStringIgnoreCodeAndKeyword("LogFileOutputPath", logger.LoggerName, displayPaths));


This should be under a changewave, in case it breaks someone and we need to change it to be more opt-in.

I think I did it? I need a review if I did it correctly as it is my first time working with that.

Added a message of enabled logs, and their paths.

a93b3f1

JanProvaznik reviewed Apr 20, 2026

View reviewed changes

Comment thread src/Build/BackEnd/Components/Logging/LoggingServiceLogMethods.cs Outdated

Aleš Prokop added 4 commits April 20, 2026 15:24

separated the function, added interface for handling file names

49bb7f1

First draft of paths of logs in BuildSummary.

6f3fbbd

Added clickable links into the build summary.

54be972

messages added into summary. added files into binarylog.

1f7c117

AlesProkop marked this pull request as ready for review April 23, 2026 06:16

Copilot AI review requested due to automatic review settings April 23, 2026 06:16

Copilot started reviewing on behalf of AlesProkop April 23, 2026 06:17 View session

Copilot AI reviewed Apr 23, 2026

View reviewed changes

adressed copilot review

a598edd

AR-May reviewed Apr 23, 2026

View reviewed changes

adressed build issues and comments

4aff18e

MichalPavlik reviewed Apr 23, 2026

View reviewed changes

Comment thread src/Build/Logging/ParallelLogger/ParallelConsoleLogger.cs Outdated

MichalPavlik reviewed Apr 23, 2026

View reviewed changes

Comment thread src/Framework/LoggerRegisteredEventArgs.cs Outdated

Aleš Prokop added 2 commits April 23, 2026 16:34

changed inheritance, added binary log handling

f3037a6

adressed failing unit tests

98219f3

AR-May reviewed May 4, 2026

View reviewed changes

This was referenced May 4, 2026

Expose operational counters #12695

Closed

Rewrite resolveprojectreferences MSBuild calls to reduce the amount of batching done #12631

Closed

Aleš Prokop and others added 5 commits May 5, 2026 15:41

adressing comments

b9209d2

Merge branch 'main' into notify-file-names-of-logs

3c610fb

fixed localization files

875ce4f

updated xlf

04acb06

fix failing unit tests

7e2f60f

baronfel reviewed May 8, 2026

View reviewed changes

rainersigwald reviewed May 8, 2026

View reviewed changes

addressing comments

42b7457

github-actions Bot mentioned this pull request May 11, 2026

Add CI/CD provider-specific loggers for GitHub Actions, Azure DevOps, and GitLab #12738

Closed

rainersigwald reviewed May 12, 2026

View reviewed changes

Comment thread src/Build/BackEnd/Components/Logging/LoggingServiceLogMethods.cs Outdated

Comment thread src/Framework/Resources/SR.resx Outdated

collapsed registration, reverted xlf,resx

5a46865

AlesProkop requested review from AR-May and rainersigwald May 12, 2026 06:47

Conversation

AlesProkop commented Apr 20, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Context

Changes Made

LoggingServiceLogMethods.cs

LoggerRegisteredEventArgs.cs

ParallelConsoleLogger.cs

TerminalLogger.cs

FileLogger.cs

Testing

Examples

BinaryLogger, FileLogger, ConsoleLogger

In the console log, we have clickable links:

In the file log, we have

Currently, the BinLogger logs its path in its own way but we can see the enabled logs (this will be the same if we enable higher verbosity in all of the logs.)

BinaryLogger, FileLogger, TerminalLogger

In the terminal log, /tlp:summary has to be enabled, otherwise, it will not show (this is consistent with how other messages are handled in the TerminalLogger)

Uh oh!

AlesProkop commented Apr 20, 2026

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

JanProvaznik commented Apr 28, 2026

Uh oh!

AlesProkop commented Apr 28, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

rainersigwald left a comment

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

AlesProkop commented Apr 20, 2026 •

edited

Loading

In the terminal log, `/tlp:summary` has to be enabled, otherwise, it will not show (this is consistent with how other messages are handled in the TerminalLogger)

AlesProkop commented Apr 28, 2026 •

edited

Loading