Add Scala library rule.

--
MOS_MIGRATED_REVID=102038201

tools/build_defs/scala/README.md

@@ -0,0 +1,17 @@
+# Scala Rules for Bazel
+
+## Overview
+
+This rule is used for building [Scala][scala] projects with Bazel. There is
+currently only one rule, `scala_library`. More features will be added in the
+future, e.g. `scala_binary`, `scala_test`, etc.
+
+[scala]: http://www.scala-lang.org/
+
+### `scala_library`
+
+`scala_library` generates a `.jar` file from `.scala` source files. In order to
+make a java rule use this jar file, use the `java_import` rule.
+
+The current implementation assumes that the files `/usr/bin/scalac` and
+`/usr/share/java/scala-library.jar` exist.

tools/build_defs/scala/scala.bzl

@@ -0,0 +1,97 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Rules for supporting the Scala language."""
+
+
+_scala_filetype = FileType([".scala"])
+
+# TODO(bazel-team): Add local_repository to properly declare the dependency.
+_scala_library_path = "/usr/share/java/scala-library.jar"
+_scalac_path = "/usr/bin/scalac"
+
+def _compile(ctx, jars):
+  cmd = """
+mkdir -p {out}_tmp
+{scalac} -classpath "{jars}" $@ -d {out}_tmp &&
+# Make jar file deterministic by setting the timestamp of files
+touch -t 198001010000 $(find .)
+jar cmf {manifest} {out} -C {out}_tmp .
+"""
+  cmd = cmd.format(
+      scalac=_scalac_path,
+      out=ctx.outputs.jar.path,
+      manifest=ctx.outputs.manifest.path,
+      jars=':'.join([j.path for j in jars]))
+
+  ctx.action(
+      inputs=list(jars) + ctx.files.srcs + [ctx.outputs.manifest],
+      outputs=[ctx.outputs.jar],
+      command=cmd,
+      progress_message="scala %s" % ctx.label,
+      arguments=[f.path for f in ctx.files.srcs])
+
+
+def _write_manifest(ctx):
+  manifest = """Main-Class: {main_class}
+Class-Path: {cp}
+"""
+  manifest = manifest.format(
+      main_class=ctx.attr.main_class,
+      cp=_scala_library_path)
+
+  ctx.file_action(
+      output = ctx.outputs.manifest,
+      content = manifest)
+
+
+def _collect_jars(ctx):
+  jars = set()
+  for target in ctx.attr.deps:
+    if hasattr(target, "jar_files"):
+      jars += target.jar_files
+    elif hasattr(target, "java"):
+      jars += target.java.transitive_runtime_deps
+  return jars
+
+
+def _scala_library_impl(ctx):
+  jars = _collect_jars(ctx)
+  _write_manifest(ctx)
+  _compile(ctx, jars)
+
+  all_jars = jars + [ctx.outputs.jar]
+
+  runfiles = ctx.runfiles(
+      files = list(all_jars) + [ctx.outputs.jar],
+      collect_data = True)
+  return struct(
+      files=all_jars,
+      jar_files=all_jars,
+      runfiles=runfiles)
+
+
+scala_library = rule(
+  implementation=_scala_library_impl,
+  attrs={
+      "main_class": attr.string(mandatory=True),
+      "srcs": attr.label_list(allow_files=_scala_filetype),
+      "deps": attr.label_list(),
+      "data": attr.label_list(allow_files=True, cfg=DATA_CFG),
+      },
+  outputs={
+      "jar": "%{name}_deploy.jar",
+      "manifest": "%{name}_MANIFEST.MF",
+      },
+)

tools/build_defs/scala/test/BUILD

@@ -0,0 +1,28 @@
+load("/tools/build_defs/scala/scala", "scala_library")
+
+java_binary(
+    name = "Hello",
+    srcs = ["Hello.java"],
+    main_class = "scala.test.Hello",
+    deps = [":lib_import"],
+)
+
+# TODO(bazel-team): Allow java rules to depend directly on scala_library.
+# For now, we have to use a java_import proxy.
+java_import(
+    name = "lib_import",
+    jars = [":HelloLib"],
+)
+
+scala_library(
+    name = "HelloLib",
+    srcs = ["HelloLib.scala"],
+    main_class = "scala.test.HelloLib",
+    deps = ["OtherLib"],
+)
+
+scala_library(
+    name = "OtherLib",
+    srcs = ["OtherLib.scala"],
+    main_class = "scala.test.OtherLib",
+)

tools/build_defs/scala/test/Hello.java

@@ -0,0 +1,22 @@
+// Copyright 2015 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package scala.test;
+
+/** Example class */
+public class Hello {
+  public static void main(String[] args) {
+    HelloLib.printMessage("Hello");
+  }
+}

tools/build_defs/scala/test/HelloLib.scala

@@ -0,0 +1,7 @@
+package scala.test
+
+object HelloLib {
+  def printMessage(arg: String) {
+    println(arg + " " + OtherLib.getMessage())
+  }
+}

tools/build_defs/scala/test/OtherLib.scala

@@ -0,0 +1,8 @@
+package scala.test
+
+// It is just to show how a Scala library can depend on another Scala library.
+object OtherLib {
+  def getMessage(): String = {
+    return "scala!"
+  }
+}