How to debug "weird" error messages

[abergmeier]

Due to Bazels sandboxing, it seems like I get "weird" error messages like:

Symbol 'term com.typesafe' is missing from the classpath.
This symbol is required by 'value akka.actor.ActorSystem.config'.
Make sure that term typesafe is in your classpath and check for conflicting dependencies with -Ylog-classpath.
A full rebuild may help if 'ActorSystem.class' was compiled against an incompatible version of com.
val system = ActorSystem("TestSystem")

in the input file it states:

Classpath: bazel-out/k8-fastbuild/genfiles/external/com_typesafe_akka_akka_actor/jar/_ijar/jar/external/com_typesafe_akka_akka_actor/jar/akka-actor_2.11-2.5.13-ijar.jar:bazel-out/k8-fastbuild/bin/debezium-connector-teradata/executesql_ijar.jar:bazel-out/k8-fastbuild/bin/debezium-connector-teradata/row_ijar.jar:bazel-out/k8-fastbuild/bin/debezium-connector-teradata/teradataactor_ijar.jar:bazel-out/k8-fastbuild/genfiles/external/scala/_ijar/scala-library/external/scala/lib/scala-library-ijar.jar:bazel-out/k8-fastbuild/genfiles/external/scala/_ijar/scala-reflect/external/scala/lib/scala-reflect-ijar.jar:external/scalatest/jar/scalatest_2.11-2.2.6.jar
ClasspathResourceSrcs: 
EnableIjar: False
Files: debezium-connector-teradata/TeradataActorTest.scala
IjarCmdPath: 
IjarOutput: 
JarOutput: bazel-out/k8-fastbuild/bin/debezium-connector-teradata/teradataactor_test.jar
JavaFiles: 
Manifest: bazel-out/k8-fastbuild/bin/debezium-connector-teradata/teradataactor_test_MANIFEST.MF
Plugins: 
PrintCompileTime: False
ResourceDests: 
ResourceJars: 
ResourceSrcs: 
ResourceShortPaths: 
ResourceStripPrefix: 
ScalacOpts: 
SourceJars: 
DependencyAnalyzerMode: off
StatsfileOutput: bazel-out/k8-fastbuild/bin/debezium-connector-teradata/teradataactor_test.statsfile

How should one debug that problem? I had a similar error message before and then rebuilding seem to have done the trick!?

[johnynek]

These rules require you to declare all depencies you use. You don’t get transitive deps by default. It looks like you are missing some of the dependencies of akka actor.

[johnynek]

The error message from scalac is pretty unhelpful. It misleads users based on the assumptions from other build tools. Maybe we should see if we can hook in and change the error message there.

If you use —java_strict_deps=error you may get a better error message.

[abergmeier]

It looks like you are missing some of the dependencies of akka actor.

Thanks. That did help.

It misleads users based on the assumptions from other build tools.

It also misleads Bazel veterans ;).

[ittaiz]

@abergmeier did you try --java_strict_deps=error?

[abergmeier]

I think there is no --java_strict_deps?
Still no idea how to debug these errors in any good way :(

[ittaiz]

I actually disagree. We’ve done a lot of work on this (though it’s definitely not complete). Specifically over the past few months @Jamie5 has advanced this area greatly.
If you can take a look at the readme and specifically optionB.
We’d love to hear your feedback.

[abergmeier]

Gave option B a spin and it reduced some noise.
It also made a few things worse (I assume bugs).
For example now I get an error:

error: Target '@maven//:com_typesafe_scala_logging_scala_logging_api_2_11' is specified as a dependency to //:report but isn't used, please remove it from the deps.
You can use the following buildozer command:
buildozer 'remove deps @maven//:com_typesafe_scala_logging_scala_logging_api_2_11' //:report
src/main/scala/Foo.scala:19: error: Target 'Unknown label of file bazel-out/k8-fastbuild/bin/external/maven/v1/https/jcenter.bintray.com/org/slf4j/slf4j-api/1.7.30/stamped_slf4j-api-1.7.30.jar which came from @maven//:com_typesafe_scala_logging_scala_logging_slf4j_2_11' is used but isn't explicitly declared, please add it to the deps.
You can use the following buildozer command:
buildozer 'add deps Unknown label of file bazel-out/k8-fastbuild/bin/external/maven/v1/https/jcenter.bintray.com/org/slf4j/slf4j-api/1.7.30/stamped_slf4j-api-1.7.30.jar which came from @maven//:com_typesafe_scala_logging_scala_logging_slf4j_2_11' //:report
      logger.warn("Foo.")
                 ^
src/main/scala/Bar.scala:18: error: Target 'Unknown label of file bazel-out/k8-fastbuild/bin/external/maven/v1/https/jcenter.bintray.com/org/scala-lang/scala-library/2.11.12/stamped_scala-library-2.11.12.jar which came from @maven//:com_fasterxml_jackson_module_jackson_module_scala_2_11' is used but isn't explicitly declared, please add it to the deps.
You can use the following buildozer command:
buildozer 'add deps Unknown label of file bazel-out/k8-fastbuild/bin/external/maven/v1/https/jcenter.bintray.com/org/scala-lang/scala-library/2.11.12/stamped_scala-library-2.11.12.jar which came from @maven//:com_fasterxml_jackson_module_jackson_module_scala_2_11' //:report
}

which has a too high noise to signal ratio for me. (Would help to shorten the paths and to remap the jars to maven).
And I cannot figure out what is wrong with my scala_library:

scala_library(
    name = "report",
    srcs = [
        "src/main/scala/Bar.scala",
        "src/main/scala/Foo.scala",
    ],
    deps = [
        "@maven//:com_fasterxml_jackson_core_jackson_databind",
        "@maven//:com_fasterxml_jackson_module_jackson_module_scala_2_11",
        "@maven//:com_typesafe_scala_logging_scala_logging_api_2_11",
        "@maven//:com_typesafe_scala_logging_scala_logging_slf4j_2_11",
        "@maven//:joda_time_joda_time",
        "@maven//:org_scalaj_scalaj_http_2_11",
    ],
)

[liucijus]

rules_scala since #1183 supports loading target labels from stamped jars. For example with rules_jvm_external external jars can be stamped with --@rules_jvm_external//settings:stamp_manifest=True setting.

bazel build --@rules_jvm_external//settings:stamp_manifest=True //...

scala_import stamps imported jars since #1160