Support empty srcs

.gitignore

@@ -0,0 +1 @@
+bazel-*

scala/scala.bzl

@@ -26,6 +26,40 @@ def _adjust_resources_path(path):
     return dir_1 + dir_2, rel_path
   return "", path
 
+def _build_nosrc_jar(ctx, buildijar):
+  res_cmd = ""
+  for f in ctx.files.resources:
+    c_dir, res_path = _adjust_resources_path(f.path)
+    change_dir = "-C " + c_dir if c_dir else ""
+    res_cmd = "\n{jar} uf {out} " + change_dir + " " + res_path
+  ijar_cmd = ""
+  if buildijar:
+    ijar_cmd = "\ncp {out} {ijar_out}".format(
+      out=ctx.outputs.jar.path,
+      ijar_out=ctx.outputs.ijar.path)
+  cmd = """
+set -e
+# Make jar file deterministic by setting the timestamp of files
+touch -t 198001010000 {manifest}
+{jar} cmf {manifest} {out}
+""" + ijar_cmd + res_cmd
+  cmd = cmd.format(
+      out=ctx.outputs.jar.path,
+      manifest=ctx.outputs.manifest.path,
+      jar=ctx.file._jar.path)
+  outs = [ctx.outputs.jar]
+  if buildijar:
+    outs.extend([ctx.outputs.ijar])
+  ctx.action(
+      inputs=
+          ctx.files.resources +
+          ctx.files._jdk +
+          [ctx.outputs.manifest, ctx.file._jar],
+      outputs=outs,
+      command=cmd,
+      progress_message="scala %s" % ctx.label,
+      arguments=[])
+
 def _compile(ctx, jars, buildijar):
   res_cmd = ""
   for f in ctx.files.resources:
@@ -71,6 +105,21 @@ touch -t 198001010000 {manifest}
       progress_message="scala %s" % ctx.label,
       arguments=[f.path for f in ctx.files.srcs])
 
+def _compile_or_empty(ctx, jars, buildijar):
+  if len(ctx.files.srcs) == 0:
+    _build_nosrc_jar(ctx, buildijar)
+    #  no need to build ijar when empty
+    return struct(ijar=ctx.outputs.jar, class_jar=ctx.outputs.jar)
+  else:
+    _compile(ctx, jars, buildijar)
+    ijar = None
+    if buildijar:
+      ijar = ctx.outputs.ijar
+    else:
+      #  macro code needs to be available at compile-time, so set ijar == jar
+      ijar = ctx.outputs.jar
+    return struct(ijar=ijar, class_jar=ctx.outputs.jar)
+
 def _write_manifest(ctx):
   # TODO(bazel-team): I don't think this classpath is what you want
   manifest = "Class-Path: %s\n" % ctx.file._scalalib.path
@@ -142,24 +191,22 @@ def _collect_jars(targets):
       compile_jars += target.files
   return struct(compiletime = compile_jars, runtime = runtime_jars)
 
-def _lib(ctx, use_ijar):
+def _lib(ctx, non_macro_lib):
   jars = _collect_jars(ctx.attr.deps)
   (cjars, rjars) = (jars.compiletime, jars.runtime)
   _write_manifest(ctx)
-  _compile(ctx, cjars, use_ijar)
+  outputs = _compile_or_empty(ctx, cjars, non_macro_lib)
 
   rjars += [ctx.outputs.jar]
   rjars += _collect_jars(ctx.attr.runtime_deps).runtime
 
-  ijar = None
-  if use_ijar:
-    ijar = ctx.outputs.ijar
-  else:
-    # macro code needs to be available at compile-time, so set ijar == jar
-    ijar = ctx.outputs.jar
+  if not non_macro_lib:
+    #  macros need the scala reflect jar
+    cjars += [ctx.file._scalareflect]
+    rjars += [ctx.file._scalareflect]
 
   texp = _collect_jars(ctx.attr.exports)
-  scalaattr = struct(outputs = struct(ijar=ijar, class_jar=ctx.outputs.jar),
+  scalaattr = struct(outputs = outputs,
                      transitive_runtime_deps = rjars,
                      transitive_compile_exports = texp.compiletime,
                      transitive_runtime_exports = texp.runtime
@@ -180,7 +227,7 @@ def _scala_macro_library_impl(ctx):
 # Common code shared by all scala binary implementations.
 def _scala_binary_common(ctx, cjars, rjars):
   _write_manifest(ctx)
-  _compile(ctx, cjars, False)  # no need to build an ijar for an executable
+  _compile_or_empty(ctx, cjars, False)  # no need to build an ijar for an executable
 
   runfiles = ctx.runfiles(
       files = list(rjars) + [ctx.outputs.executable] + [ctx.file._java] + ctx.files._jdk,
@@ -221,8 +268,7 @@ _implicit_deps = {
 # Common attributes reused across multiple rules.
 _common_attrs = {
   "srcs": attr.label_list(
-      allow_files=_scala_filetype,
-      non_empty=True),
+      allow_files=_scala_filetype),
   "deps": attr.label_list(),
   "runtime_deps": attr.label_list(),
   "data": attr.label_list(allow_files=True, cfg=DATA_CFG),
@@ -249,7 +295,6 @@ scala_macro_library = rule(
   attrs={
       "main_class": attr.string(),
       "exports": attr.label_list(allow_files=False),
-      "_scala-reflect": attr.label(default=Label("@scala//:lib/scala-reflect.jar"), single_file=True, allow_files=True),
       } + _implicit_deps + _common_attrs,
   outputs={
       "jar": "%{name}_deploy.jar",

test/BUILD

@@ -1,4 +1,4 @@
-load("//scala:scala.bzl", "scala_binary", "scala_library", "scala_test")
+load("//scala:scala.bzl", "scala_binary", "scala_library", "scala_test", "scala_macro_library")
 
 # The examples below show how to combine Scala and Java rules.
 # ScalaBinary is the Scala equivalent of JavaBinary.
@@ -21,7 +21,7 @@ scala_binary(
     name = "ScalaBinary",
     srcs = ["ScalaBinary.scala"],
     main_class = "scala.test.ScalaBinary",
-    deps = [":HelloLib"],
+    deps = [":HelloLib", ":MacroTest"],
 )
 
 scala_library(
@@ -30,6 +30,7 @@ scala_library(
     deps = [
         "OtherJavaLib",
         "OtherLib",
+        "MacroTest"
     ],
 )
 
@@ -49,7 +50,13 @@ scala_test(
 scala_library(
     name = "OtherLib",
     srcs = ["OtherLib.scala"],
-    exports = ["Exported"],  # test of exported target
+    exports = ["ExportOnly"],  # test of exported target
+)
+
+# Test of library without src
+scala_library(
+    name = "ExportOnly",
+    exports = [ "Exported" ],
 )
 
 scala_library(
@@ -58,6 +65,11 @@ scala_library(
     runtime_deps = ["Runtime"],
 )
 
+scala_macro_library(
+  name = "MacroTest",
+  srcs = ["MacroTest.scala"]
+)
+
 scala_library(
     name = "Runtime",
     srcs = ["Runtime.scala"],

test/HelloLib.scala

@@ -16,6 +16,7 @@ package scala.test
 
 object HelloLib {
   def printMessage(arg: String) {
+    MacroTest.hello(arg == "yo")
     println(getOtherLibMessage(arg))
     println(getOtherJavaLibMessage(arg))
     println(Exported.message)

test/MacroTest.scala

@@ -0,0 +1,17 @@
+package scala.test
+
+import language.experimental.macros
+
+import reflect.macros.Context
+
+object MacroTest {
+  def hello(param: Any): Unit = macro hello_impl
+
+  def hello_impl(c: Context)(param: c.Expr[Any]): c.Expr[Unit] = {
+    import c.universe._
+    val paramRep = show(param.tree)
+    val paramRepTree = Literal(Constant(paramRep))
+    val paramRepExpr = c.Expr[String](paramRepTree)
+    reify { println(paramRepExpr.splice + " = " + param.splice) }
+  }
+}

test/ScalaBinary.scala

@@ -16,6 +16,7 @@ package scala.test
 
 object ScalaBinary {
   def main(args: Array[String]) {
+    println(MacroTest.hello(1 + 2))
     HelloLib.printMessage("Hello");
   }
 }