Added a message of enabled logs, and their paths.

[AlesProkop]

Fixes #12261

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]

@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]

@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]

@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.

[AR-May]

@baronfel should we try to make those links in console logger summary? I think there might be terminals in which those ansi codes would not work and we would not want them to be malformed?

[AR-May]

@rainersigwald Could you please take a look at whether deriving LoggerRegisteredEventArgs from BuildStatusEventArgs makes sense? Is there a better place for it in the event args hierarchy?