我尝试在 Bazel 中编译一个 Scala 库。这会导致错误：
error: Symbol 'type <none>.slf4j.Logger' is missing from the classpath.
This symbol is required by 'value com.typesafe.scalalogging.slf4j.Logger.underlying'.
Make sure that type Logger is in your classpath and check for conflicting dependencies with `-Ylog-classpath`.
A full rebuild may help if 'Logger.class' was compiled against an incompatible version of <none>.slf4j.
logger.warn("Foo")
^
one error found
one error found
java.lang.RuntimeException: Build failed
at io.bazel.rulesscala.scalac.ScalacProcessor.compileScalaSources(ScalacProcessor.java:256)
at io.bazel.rulesscala.scalac.ScalacProcessor.processRequest(ScalacProcessor.java:76)
at io.bazel.rulesscala.worker.GenericWorker.runPersistentWorker(GenericWorker.java:45)
at io.bazel.rulesscala.worker.GenericWorker.run(GenericWorker.java:111)
at io.bazel.rulesscala.scalac.ScalaCInvoker.main(ScalaCInvoker.java:41)
我的BUILD.bazel样子是这样的：
load("@io_bazel_rules_scala//scala:scala.bzl", "scala_library")
scala_library(
name = "foo",
srcs = [
"src/main/scala/Foo.scala",
],
deps = [
"@maven//:com_fasterxml_jackson_core_jackson_core",
"@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",
],
)
根据我的阅读，这个错误通常源于混合 2.x 和 2.y Scala 版本。不过，我一生都无法弄清楚我会在哪里做这件事。