Scala rules: Implement scala_binary

--
MOS_MIGRATED_REVID=102837474

7 files changed, 123 insertions, 18 deletions

diff --git a/tools/build_defs/scala/README.md b/tools/build_defs/scala/README.md
index be8ede2e1d..2a0287812b 100644
--- a/tools/build_defs/scala/README.md
+++ b/tools/build_defs/scala/README.md
@@ -2,16 +2,23 @@
 
 ## 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.
+This rule is used for building [Scala][scala] projects with Bazel. There are
+currently two rules, `scala_library` and `scala_binary`. More features will be
+added in the future, e.g. `scala_test`.
 
 [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.
+`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.
+
+### `scala_binary`
+
+`scala_binary` generates a Scala executable. It may depend on `scala_library`
+and `java_library` rules.
+
+A `scala_binary` requires a `main_class` attribute.
diff --git a/tools/build_defs/scala/scala.bzl b/tools/build_defs/scala/scala.bzl
index 0f23bb1ea3..222573db8f 100644
--- a/tools/build_defs/scala/scala.bzl
+++ b/tools/build_defs/scala/scala.bzl
@@ -23,8 +23,9 @@ _scalac_path = "/usr/bin/scalac"
 
 def _compile(ctx, jars):
   cmd = """
+set -e
 mkdir -p {out}_tmp
-{scalac} -classpath "{jars}" $@ -d {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 .
@@ -33,7 +34,7 @@ jar cmf {manifest} {out} -C {out}_tmp .
       scalac=_scalac_path,
       out=ctx.outputs.jar.path,
       manifest=ctx.outputs.manifest.path,
-      jars=':'.join([j.path for j in jars]))
+      jars=":".join([j.path for j in jars]))
 
   ctx.action(
       inputs=list(jars) + ctx.files.srcs + [ctx.outputs.manifest],
@@ -54,6 +55,20 @@ def _write_manifest(ctx):
       content = manifest)
 
 
+def _write_launcher(ctx, jars):
+  content = """#!/bin/bash
+cd $0.runfiles
+java -cp {cp} {name} "$@"
+"""
+  content = content.format(
+      name=ctx.attr.main_class,
+      deploy_jar=ctx.outputs.jar.path,
+      cp=":".join([j.short_path for j in jars]))
+  ctx.file_action(
+      output=ctx.outputs.executable,
+      content=content)
+
+
 def _collect_jars(ctx):
   jars = set()
   for target in ctx.attr.deps:
@@ -69,21 +84,55 @@ def _scala_library_impl(ctx):
   _write_manifest(ctx)
   _compile(ctx, jars)
 
-  all_jars = jars + [ctx.outputs.jar]
+  jars += [ctx.outputs.jar]
+  runfiles = ctx.runfiles(
+      files = list(jars),
+      collect_data = True)
+  return struct(
+      files=jars,
+      jar_files=jars,
+      runfiles=runfiles)
+
+
+def _scala_binary_impl(ctx):
+  jars = _collect_jars(ctx)
+  _write_manifest(ctx)
+  _compile(ctx, jars)
+
+  jars += [ctx.outputs.jar]
+  _write_launcher(ctx, jars)
 
   runfiles = ctx.runfiles(
-      files = list(all_jars) + [ctx.outputs.jar],
+      files = list(jars) + [ctx.outputs.executable],
       collect_data = True)
   return struct(
-      files=all_jars,
-      jar_files=all_jars,
+      files=set([ctx.outputs.executable]),
       runfiles=runfiles)
 
 
 scala_library = rule(
   implementation=_scala_library_impl,
   attrs={
-      "srcs": attr.label_list(allow_files=_scala_filetype),
+      "main_class": attr.string(),
+      "srcs": attr.label_list(
+          allow_files=_scala_filetype,
+          non_empty=True),
+      "deps": attr.label_list(),
+      "data": attr.label_list(allow_files=True, cfg=DATA_CFG),
+      },
+  outputs={
+      "jar": "%{name}_deploy.jar",
+      "manifest": "%{name}_MANIFEST.MF",
+      },
+)
+
+scala_binary = rule(
+  implementation=_scala_binary_impl,
+  attrs={
+      "main_class": attr.string(mandatory=True),
+      "srcs": attr.label_list(
+          allow_files=_scala_filetype,
+          non_empty=True),
       "deps": attr.label_list(),
       "data": attr.label_list(allow_files=True, cfg=DATA_CFG),
       },
@@ -91,4 +140,5 @@ scala_library = rule(
       "jar": "%{name}_deploy.jar",
       "manifest": "%{name}_MANIFEST.MF",
       },
+  executable=True,
 )
diff --git a/tools/build_defs/scala/test/BUILD b/tools/build_defs/scala/test/BUILD
index 6eebffb7d1..8e6c47e71d 100644
--- a/tools/build_defs/scala/test/BUILD
+++ b/tools/build_defs/scala/test/BUILD
@@ -1,9 +1,12 @@
-load("/tools/build_defs/scala/scala", "scala_library")
+load("/tools/build_defs/scala/scala", "scala_binary", "scala_library")
+
+# The examples below show how to combine Scala and Java rules.
+# ScalaBinary is the Scala equivalent of JavaBinary.
 
 java_binary(
-    name = "Hello",
-    srcs = ["Hello.java"],
-    main_class = "scala.test.Hello",
+    name = "JavaBinary",
+    srcs = ["JavaBinary.java"],
+    main_class = "scala.test.JavaBinary",
     deps = [":lib_import"],
 )
 
@@ -14,13 +17,28 @@ java_import(
     jars = [":HelloLib"],
 )
 
+scala_binary(
+    name = "ScalaBinary",
+    srcs = ["ScalaBinary.scala"],
+    main_class = "scala.test.ScalaBinary",
+    deps = [":HelloLib"],
+)
+
 scala_library(
     name = "HelloLib",
     srcs = ["HelloLib.scala"],
-    deps = ["OtherLib"],
+    deps = [
+        "OtherJavaLib",
+        "OtherLib",
+    ],
 )
 
 scala_library(
     name = "OtherLib",
     srcs = ["OtherLib.scala"],
 )
+
+java_library(
+    name = "OtherJavaLib",
+    srcs = ["OtherJavaLib.java"],
+)
diff --git a/tools/build_defs/scala/test/HelloLib.scala b/tools/build_defs/scala/test/HelloLib.scala
index afd4ec2f07..88db4546ac 100644
--- a/tools/build_defs/scala/test/HelloLib.scala
+++ b/tools/build_defs/scala/test/HelloLib.scala
@@ -3,5 +3,6 @@ package scala.test
 object HelloLib {
   def printMessage(arg: String) {
     println(arg + " " + OtherLib.getMessage())
+    println(arg + " " + OtherJavaLib.getMessage())
   }
 }
diff --git a/tools/build_defs/scala/test/Hello.java b/tools/build_defs/scala/test/JavaBinary.java
index 55baa73868..69e8900be8 100644
--- a/tools/build_defs/scala/test/Hello.java
+++ b/tools/build_defs/scala/test/JavaBinary.java
@@ -15,7 +15,7 @@
 package scala.test;
 
 /** Example class */
-public class Hello {
+public class JavaBinary {
   public static void main(String[] args) {
     HelloLib.printMessage("Hello");
   }
diff --git a/tools/build_defs/scala/test/OtherJavaLib.java b/tools/build_defs/scala/test/OtherJavaLib.java
new file mode 100644
index 0000000000..8b5968c69f
--- /dev/null
+++ b/tools/build_defs/scala/test/OtherJavaLib.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 OtherJavaLib {
+  public static String getMessage() {
+    return "java!";
+  }
+}
diff --git a/tools/build_defs/scala/test/ScalaBinary.scala b/tools/build_defs/scala/test/ScalaBinary.scala
new file mode 100644
index 0000000000..5b023a97de
--- /dev/null
+++ b/tools/build_defs/scala/test/ScalaBinary.scala
@@ -0,0 +1,7 @@
+package scala.test
+
+object ScalaBinary {
+  def main(args: Array[String]) {
+    HelloLib.printMessage("Hello");
+  }
+}