Attempt to use an External Dependency

[promiseofcake]

We currently have a working build for scala_library and scala_test targets. This PR will illustrate how the new SimpleParser main class external dependencies are not used for scala_test targets.

cef927d:

• Import org_scala_lang_scala_parser_combinators
• Add a SimpleParser example for scala.util.parsing.combinator._

6b27703:

• Add the external dependency to the scala_test target and see it succeed.

[promiseofcake]

When running on cef927d:

$ bazel build //src/main/scala/Sample:simple_parser 
INFO: Analysed target //src/main/scala/Sample:simple_parser.
INFO: Found 1 target...
Target //src/main/scala/Sample:simple_parser up-to-date:
  bazel-bin/src/main/scala/Sample/simple_parser.jar
INFO: Elapsed time: 0.286s, Critical Path: 0.00s
INFO: Build completed successfully, 1 total action

$ bazel test //src/test/scala/Sample:simple_parser_test 
INFO: Analysed target //src/test/scala/Sample:simple_parser_test.
INFO: Found 1 test target...
ERROR: /Users/lucas/Workspace/repos/promiseofcake/scala-test/src/test/scala/Sample/BUILD:14:1: scala //src/test/scala/Sample:simple_parser_test failed (Exit 1): scalac failed: error executing command 
  (cd /private/var/tmp/_bazel_lucas/38ce124245a89f3c8f10f0656b79414e/execroot/__main__ && \
  exec env - \
  bazel-out/host/bin/external/io_bazel_rules_scala/src/java/io/bazel/rulesscala/scalac/scalac @bazel-out/darwin_x86_64-fastbuild/bin/src/test/scala/Sample/simple_parser_test_worker_input)
src/test/scala/Sample/SimpleParserTest.scala:7: error: Symbol 'term scala.util.parsing' is missing from the classpath.
This symbol is required by 'object Sample.SimpleParser'.
Make sure that term parsing is in your classpath and check for conflicting dependencies with `-Ylog-classpath`.
A full rebuild may help if 'SimpleParser.class' was compiled against an incompatible version of scala.util.
(NOTE: It looks like the scala-parser-combinators module is missing; try adding a dependency on "org.scala-lang.modules" : "scala-parser-combinators".
       See http://docs.scala-lang.org/overviews/ for more information.)
    SimpleParser.parse(SimpleParser.word, "johnny come lately")
    ^
src/test/scala/Sample/SimpleParserTest.scala:7: error: value parse is not a member of object Sample.SimpleParser
    SimpleParser.parse(SimpleParser.word, "johnny come lately")
                 ^
two errors found
two errors 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:68)
        at io.bazel.rulesscala.worker.GenericWorker.run(GenericWorker.java:125)
        at io.bazel.rulesscala.scalac.ScalaCInvoker.main(ScalaCInvoker.java:41)
Target //src/test/scala/Sample:simple_parser_test failed to build
INFO: Elapsed time: 1.817s, Critical Path: 1.72s
FAILED: Build did NOT complete successfully

Executed 0 out of 1 test: 1 fails to build.

[promiseofcake]

When running on 6b27703:

Which adds org_scala_lang_scala_parser_combinators to the test deps.

scala_test(
    name = "simple_parser_test",
    size = "small",
    srcs = ["SimpleParserTest.scala"],
    deps = [
        "//src/main/scala/Sample:simple_parser",
        "@org_scala_lang_scala_parser_combinators//jar"
    ],
)

$ bazel build //src/main/scala/Sample:simple_parser 
INFO: Analysed target //src/main/scala/Sample:simple_parser.
INFO: Found 1 target...
Target //src/main/scala/Sample:simple_parser up-to-date:
  bazel-bin/src/main/scala/Sample/simple_parser.jar
INFO: Elapsed time: 0.090s, Critical Path: 0.00s
INFO: Build completed successfully, 1 total action

$ bazel test //src/test/scala/Sample:simple_parser_test 
INFO: Analysed target //src/test/scala/Sample:simple_parser_test.
INFO: Found 1 test target...
Target //src/test/scala/Sample:simple_parser_test up-to-date:
  bazel-bin/src/test/scala/Sample/simple_parser_test
INFO: Elapsed time: 2.693s, Critical Path: 2.59s
INFO: Build completed successfully, 3 total actions

Executed 1 out of 1 test: 1 test passes.