Do not use File objects in dictionary keys

[aherrmann]

The function cc_library_key generates the dictionary keys by which LibLibraryToLink are mapped to their corresponding HaskellCcLibraryInfo. Before this used a struct over None or File objects. This changes uses None or string instead, where string is the .path attribute of the File object.

Using a File object in a dictionary key fails if the File object used at lookup time is semantically the same, but has a different identity due to implementation details in Bazel.

Closes #1536

[meteorcloudy]

Tested with Bazel@HEAD: https://buildkite.com/bazel/rules-haskell-haskell/builds/725

[facundominguez]

Maybe this could go as a local definition inside of cc_library_key.

[aherrmann]

Done.

[aherrmann]

Never mind, this is not allowed in Bazel 4.0.0:

ERROR: /home/runner/.cache/bazel/_bazel_runner/3e6d0af2c61b2bb9852d7167e763fc51/external/rules_haskell/haskell/private/cc_libraries.bzl:247:5: nested functions are not allowed. Move the function to the top level.
ERROR: error loading package '': in /home/runner/.cache/bazel/_bazel_runner/3e6d0af2c61b2bb9852d7167e763fc51/external/rules_haskell/haskell/cabal.bzl: Extension 'haskell/private/cc_libraries.bzl' has errors

It seems to be allowed in Bazel HEAD though, the change worked when tested with USE_BAZEL_VERSION="last_green".

[aherrmann]

Encountered an issue with BES on Windows:

FATAL: bazel crashed due to an internal error. Printing stack trace:
java.util.concurrent.RejectedExecutionException: Task com.google.common.util.concurrent.TrustedListenableFutureTask@7eb86512[status=PENDING, info=[task=[running=[NOT STARTED YET], com.google.devtools.build.lib.remote.ByteStreamBuildEventArtifactUploader$$Lambda$737/0x00000001007d2c40@6e4e775f]]] rejected from java.util.concurrent.ThreadPoolExecutor@31968453[Terminated, pool size = 0, active threads = 0, queued tasks = 0, completed tasks = 253]
	at java.base/java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.reject(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor.execute(Unknown Source)
	at com.google.common.util.concurrent.MoreExecutors$ListeningDecorator.execute(MoreExecutors.java:586)
	at java.base/java.util.concurrent.AbstractExecutorService.submit(Unknown Source)
	at com.google.common.util.concurrent.AbstractListeningExecutorService.submit(AbstractListeningExecutorService.java:66)
	at com.google.devtools.build.lib.remote.ByteStreamBuildEventArtifactUploader.upload(ByteStreamBuildEventArtifactUploader.java:222)
	at com.google.devtools.build.lib.buildeventstream.BuildEventArtifactUploader.uploadReferencedLocalFiles(BuildEventArtifactUploader.java:104)
	at com.google.devtools.build.lib.buildeventservice.BuildEventServiceUploader.enqueueEvent(BuildEventServiceUploader.java:196)
	at com.google.devtools.build.lib.buildeventservice.BuildEventServiceTransport.sendBuildEvent(BuildEventServiceTransport.java:95)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.post(BuildEventStreamer.java:268)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.buildEvent(BuildEventStreamer.java:472)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.buildEvent(BuildEventStreamer.java:481)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.clearPendingEvents(BuildEventStreamer.java:307)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.clearEventsAndPostFinalProgress(BuildEventStreamer.java:634)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.close(BuildEventStreamer.java:354)
	at com.google.devtools.build.lib.runtime.BuildEventStreamer.closeOnAbort(BuildEventStreamer.java:336)
	at com.google.devtools.build.lib.buildeventservice.BuildEventServiceModule.forceShutdownBuildEventStreamer(BuildEventServiceModule.java:409)
	at com.google.devtools.build.lib.buildeventservice.BuildEventServiceModule.afterCommand(BuildEventServiceModule.java:578)
	at com.google.devtools.build.lib.runtime.BlazeRuntime.afterCommand(BlazeRuntime.java:626)
	at com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.execExclusively(BlazeCommandDispatcher.java:603)
	at com.google.devtools.build.lib.runtime.BlazeCommandDispatcher.exec(BlazeCommandDispatcher.java:231)
	at com.google.devtools.build.lib.server.GrpcServerImpl.executeCommand(GrpcServerImpl.java:543)
	at com.google.devtools.build.lib.server.GrpcServerImpl.lambda$run$1(GrpcServerImpl.java:606)
	at io.grpc.Context$1.run(Context.java:579)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.base/java.lang.Thread.run(Unknown Source)
Error: Process completed with exit code 37.

Possibly related to bazelbuild/bazel#12575.

Retrying...