✅ add support for Windows

[ryandens]

Add Windows support to javaagent application distribution plugin

• Introduces a new Platform enum with per-platform constants (line separator, path separator, app home variable, JVM opts format) for Unix and Windows.
• Updates JavaagentAwareStartScriptGenerator to accept a Platform parameter, generating correct -javaagent paths and DEFAULT_JVM_OPTS format for each OS.
• Updates JavaagentApplicationDistributionPlugin to use JavaagentAwareStartScriptGenerator for both Unix and Windows, replacing the previous no-op WindowsStartScriptGenerator.
• CI matrix in gradle.yml now runs builds on both ubuntu-latest and windows-latest.
• Functional tests are updated to handle OS-specific paths, script extensions, and expected script content; on Windows, TestKit uses a short root path to avoid MAX_PATH issues.
• Behavioral Change: Windows start scripts now include -javaagent options using %APP_HOME% paths and quoted JVM opt tokens; previously Windows scripts had no javaagent support.

^{Macroscope summarized 54dca34.}

[pixee-ryandens]

Nice work! ✅ I analyzed your pull request and don't see any hardening opportunities.

[neboskreb]

@ryandens this PR seems a bit stuck. Would you like some assistance? I'd gladly help to move it forward.

[ryandens]

@neboskreb feel free! i just rebased it with main. I don't have a windows machine accessible, so getting the integration tests to pass on windows is a bit painful.

[neboskreb]

I fixed a couple of very small bugs and it seems to work for me.

@ryandens I'd push my changes if you add me to the collaborators

[neboskreb]

@ryandens I found a way to push my commits without pushing :) Created PR #298 to "push" those 2 commits into this branch - please see and merge.

[neboskreb]

My investigation finds that the test failures in #298 come from IllegalArgumentException thrown from the internals of Java Instrumentation, probably triggered by an error condition inside or around the OpenTelemetryAgent:

Hello from my simple agent!
ERROR io.opentelemetry.javaagent.OpenTelemetryAgent
java.lang.IllegalArgumentException
	at java.instrument/sun.instrument.InstrumentationImpl.appendToClassLoaderSearch0(Native Method)
	at java.instrument/sun.instrument.InstrumentationImpl.appendToBootstrapClassLoaderSearch(InstrumentationImpl.java:276)
	at io.opentelemetry.javaagent.OpenTelemetryAgent.installBootstrapJar(OpenTelemetryAgent.java:98)
	at io.opentelemetry.javaagent.OpenTelemetryAgent.startAgent(OpenTelemetryAgent.java:56)
	at io.opentelemetry.javaagent.OpenTelemetryAgent.premain(OpenTelemetryAgent.java:46)
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104)
	at java.base/java.lang.reflect.Method.invoke(Method.java:565)
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:544)
	at java.instrument/sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:556)

Unfortunately, the exact cause of the exception is not know because OpenTelemetryAgent does not do a best job logging it, showing only the topmost layer and not printing the "caused by" part.

This error occurs only in test configuration, whereas the run configuration completes successfully.

Bumping up the version from 1.11.1 to the newest 1.23.0 brought no relief.

Also, no errors occur in test configuration if a different agent is used, for instance org.mockito:mockito-core:5.21.0 - in this case the test shows no malfunction.

@ryandens This looks to me like an Open Telemetry setup issue on Windows (or my machine?). Unfortunately, I'm not familiar with the framework. If you are, could you give me some hints to what could be wrong?

[ryandens]

Unfortunately, I also don't know what the issue was here - I also saw test failures in the javaagent-application plugin project, so I don't think this is isolated to the OpenTelemetry instrumentation agent. I could of course be mistaken. Thanks for your work on this issue, it looks like it brought it closer to the finish line.

[ryandens]

@macroscope-app review

[macroscopeapp]

Manual reviews triggered for commit 2586352:

• Approvability Check
• Correctness Check

^{All prior checks · these links stay valid even if you push more commits.}

[macroscopeapp]

Review started! I'm analyzing the pull request and will post feedback through check runs when complete.