Scala maven import external (#473)

* original jave_import_external

* allow for direct jar file usage in dependencies

* change java_import to scala_import

* replace jar_urls with artifact + server_urls

* remove filegroup target and use maven_jar for specific places that need files directly. an issue will be open for scala_import to support direct file output

* rename to scala_maven_import_external. still need to decide on splitting to jvm_import_external/maven_import_external

* _concat_with_needed_slash

* fix typo

* add 'return' in new method

* extract common code to 'jvm_import_external' rule. introduce macros for 'scala_maven_import_external', 'maven_import_external', 'java_import_external'

* CR changes

* added documentation

* moved license notice back to the top

Author: natansil

WORKSPACE

@@ -43,7 +43,7 @@ maven_jar(
 
 # test of strict deps (scalac plugin UT + E2E)
 maven_jar(
-    name = "com_google_guava_guava_21_0",
+    name = "com_google_guava_guava_21_0_with_file",
     artifact = "com.google.guava:guava:21.0",
     sha1 = "3a3d111be1be1b745edfa7d91678a12d7ed38709"
 )
@@ -83,3 +83,24 @@ filegroup(
 
 load("@io_bazel_rules_scala//scala:toolchains.bzl","scala_register_toolchains")
 scala_register_toolchains()
+
+load("//scala:scala_maven_import_external.bzl", "scala_maven_import_external", "java_import_external")
+scala_maven_import_external(
+    name = "com_google_guava_guava_21_0",
+    licenses = ["notice"],  # Apache 2.0
+    artifact = "com.google.guava:guava:21.0",
+    server_urls = ["https://mirror.bazel.build/repo1.maven.org/maven2"],
+    jar_sha256 = "972139718abc8a4893fa78cba8cf7b2c903f35c97aaf44fa3031b0669948b480",
+)
+
+# bazel's java_import_external has been altered in rules_scala to be a macro based on jvm_import_external
+# in order to allow for other jvm-language imports (e.g. scala_import)
+# the 3rd-party dependency below is using the java_import_external macro
+# in order to make sure no regression with the original java_import_external
+load("//scala:scala_maven_import_external.bzl", "java_import_external")
+java_import_external(
+    name = "org_apache_commons_commons_lang_3_5_without_file",
+    licenses = ["notice"],  # Apache 2.0
+    jar_urls = ["http://central.maven.org/maven2/org/apache/commons/commons-lang3/3.5/commons-lang3-3.5.jar"],
+    jar_sha256 = "8ac96fc686512d777fca85e144f196cd7cfe0c0aec23127229497d1a38ff651c",
+)