Add support for aar_import_external and aar_maven_import_external

Usage example:

```python
# In WORKSPACE
load("@bazel_tools//tools/build_defs/repo:android.bzl", "aar_import_external", "aar_maven_import_external")

# Specify the URL directly:
aar_import_external(
    name = "com_android_support_preference_v14_25_1_0",                              # required
    licenses = ["notice"],                                                           # required
    aar_urls = [                                                                     # required
        "https://dl.google.com/dl/android/maven2/com/android/support/preference-v14/25.1.0/preference-v14-25.1.0.aar"
    ],
    aar_sha256 = "442473fe5c395ebef26c14eb01d17ceda33ad207a4cc23a32a2ad95b87edfabb", # optional or empty string
    deps = [                                                                         # optional or empty list
        "@com_android_support_recyclerview_v7_25_1_0//aar",
        "@com_android_support_appcompat_v7_25_1_0//aar",
        "@com_android_support_preference_v7_25_1_0//aar",
        "@com_android_support_support_v4_25_1_0//aar",
    ],
)

# Or, specify the artifact coordinate:
aar_maven_import_external(
    name = "com_android_support_preference_v14_25_1_0",                         # required
    artifact = "com.android.support.test:preference-v14:25.1.0",                # required
    sha256 = "442473fe5c395ebef26c14eb01d17ceda33ad207a4cc23a32a2ad95b87edfabb" # optional or empty string
    licenses = ["notice"],                                                      # required
    server_urls = ["https://maven.google.com"],                                 # required
    deps = [                                                                    # optional or empty list
        "@com_android_support_recyclerview_v7_25_1_0//aar",
        "@com_android_support_appcompat_v7_25_1_0//aar",
        "@com_android_support_preference_v7_25_1_0//aar",
        "@com_android_support_support_v4_25_1_0//aar",
    ],
)

# In BUILD.bazel
android_library(
    name = "foo",
    srcs = [...],
    deps = [
        "@com_android_support_preference_v14_25_1_0//aar",
    ],
)
```

To test this out with gmaven_rules, change the `load` statement in https://github.com/bazelbuild/gmaven_rules/blob/master/gmaven.bzl to

```
load('@bazel_tools//tools/build_defs/repo:android.bzl', 'aar_import_external')
load('@bazel_tools//tools/build_defs/repo:java.bzl', 'java_import_external')
```

Fixes https://github.com/bazelbuild/bazel/issues/4654

RELNOTES: New rules for importing Android dependencies: `aar_import_external` and `aar_maven_import_external`. `aar_import_external` enables specifying external AAR dependencies using a list of HTTP URLs for the artifact. `aar_maven_import_external` enables specifying external AAR dependencies using the artifact coordinate and a list of server URLs.

Closes #5319.

Change-Id: I9517e68ab78f2e30fb6ceabfe3b35061c585d607
PiperOrigin-RevId: 199839047

3 files changed, 142 insertions, 32 deletions

diff --git a/tools/build_defs/repo/android.bzl b/tools/build_defs/repo/android.bzl
new file mode 100644
index 0000000000..1e0e9caf0a
--- /dev/null
+++ b/tools/build_defs/repo/android.bzl
@@ -0,0 +1,85 @@
+# Copyright 2018 The Bazel Authors. 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 importing external Android Archives (AARs).
+
+Usage:
+
+    # In WORKSPACE
+    load("@bazel_tools//tools/build_defs/repo:android.bzl", "aar_import_external", "aar_maven_import_external")
+
+    # Specify the URL directly:
+    aar_import_external(
+        name = "com_android_support_preference_v14_25_1_0",                              # required
+        licenses = ["notice"],                                                           # required
+        aar_urls = [                                                                     # required
+            "https://dl.google.com/dl/android/maven2/com/android/support/preference-v14/25.1.0/preference-v14-25.1.0.aar"
+        ],
+        aar_sha256 = "442473fe5c395ebef26c14eb01d17ceda33ad207a4cc23a32a2ad95b87edfabb", # optional or empty string
+        deps = [                                                                         # optional or empty list
+            "@com_android_support_recyclerview_v7_25_1_0//aar",
+            "@com_android_support_appcompat_v7_25_1_0//aar",
+            "@com_android_support_preference_v7_25_1_0//aar",
+            "@com_android_support_support_v4_25_1_0//aar",
+        ],
+    )
+
+    # Or, specify the artifact coordinate:
+    aar_maven_import_external(
+        name = "com_android_support_preference_v14_25_1_0",                         # required
+        artifact = "com.android.support.test:preference-v14:25.1.0",                # required
+        sha256 = "442473fe5c395ebef26c14eb01d17ceda33ad207a4cc23a32a2ad95b87edfabb" # optional or empty string
+        licenses = ["notice"],                                                      # required
+        server_urls = ["https://maven.google.com"],                                 # required
+        deps = [                                                                    # optional or empty list
+            "@com_android_support_recyclerview_v7_25_1_0//aar",
+            "@com_android_support_appcompat_v7_25_1_0//aar",
+            "@com_android_support_preference_v7_25_1_0//aar",
+            "@com_android_support_support_v4_25_1_0//aar",
+        ],
+    )
+
+    # In BUILD.bazel
+    android_library(
+        name = "foo",
+        srcs = [...],
+        deps = [
+            "@com_android_support_preference_v14_25_1_0//aar",
+        ],
+    )
+"""
+
+load(":jvm.bzl", "convert_artifact_coordinate_to_urls", "jvm_import_external")
+
+def aar_import_external(aar_sha256, aar_urls, **kwargs):
+    jvm_import_external(
+        rule_name = "aar_import",
+        rule_metadata = {
+            "extension": "aar",
+            "import_attr": "aar = %s",
+        },
+        artifact_sha256 = aar_sha256,
+        artifact_urls = aar_urls,
+        **kwargs
+    )
+
+def aar_maven_import_external(artifact, server_urls, aar_sha256 = "", **kwargs):
+    aar_import_external(
+        aar_sha256 = aar_sha256,
+        aar_urls = convert_artifact_coordinate_to_urls(
+            artifact,
+            server_urls,
+            "aar",
+        ),
+        **kwargs
+    )
diff --git a/tools/build_defs/repo/java.bzl b/tools/build_defs/repo/java.bzl
index 1e40ba4a9d..4e6ce5f03c 100644
--- a/tools/build_defs/repo/java.bzl
+++ b/tools/build_defs/repo/java.bzl
@@ -171,9 +171,10 @@ reasonably expected to already be provided.
 
 load("@bazel_tools//tools/build_defs/repo:jvm.bzl", "jvm_import_external")
 
-def java_import_external(jar_sha256, **kwargs):
+def java_import_external(jar_sha256, jar_urls, **kwargs):
     jvm_import_external(
         rule_name = "java_import",
-        jar_sha256 = jar_sha256,
+        artifact_sha256 = jar_sha256,
+        artifact_urls = jar_urls,
         **kwargs
     )
diff --git a/tools/build_defs/repo/jvm.bzl b/tools/build_defs/repo/jvm.bzl
index b0acd2417f..1538ea1b7e 100644
--- a/tools/build_defs/repo/jvm.bzl
+++ b/tools/build_defs/repo/jvm.bzl
@@ -33,6 +33,7 @@ the following macros are defined below that utilize jvm_import_external:
 """
 
 _HEADER = "# DO NOT EDIT: generated by jvm_import_external()"
+
 _PASS_PROPS = (
     "neverlink",
     "testonly_",
@@ -49,18 +50,20 @@ def _jvm_import_external(repository_ctx):
         not repository_ctx.attr.neverlink):
         fail("Only use generated_linkable_rule_name if neverlink is set")
     name = repository_ctx.attr.generated_rule_name or repository_ctx.name
-    urls = repository_ctx.attr.jar_urls
-    sha = repository_ctx.attr.jar_sha256
-    path = repository_ctx.name + ".jar"
+    urls = repository_ctx.attr.artifact_urls
+    sha = repository_ctx.attr.artifact_sha256
+    extension = repository_ctx.attr.rule_metadata["extension"]
+    file_extension = "." + extension
+    path = repository_ctx.name + file_extension
     for url in urls:
-        if url.endswith(".jar"):
+        if url.endswith(file_extension):
             path = url[url.rindex("/") + 1:]
             break
     srcurls = repository_ctx.attr.srcjar_urls
     srcsha = repository_ctx.attr.srcjar_sha256
     srcpath = repository_ctx.name + "-src.jar" if srcurls else ""
     for url in srcurls:
-        if url.endswith(".jar"):
+        if url.endswith(file_extension):
             srcpath = url[url.rindex("/") + 1:].replace("-sources.jar", "-src.jar")
             break
     lines = [_HEADER, ""]
@@ -75,24 +78,26 @@ def _jvm_import_external(repository_ctx):
     lines.append("licenses(%s)" % repr(repository_ctx.attr.licenses))
     lines.append("")
     lines.extend(_serialize_given_rule_import(
-        repository_ctx.attr.rule_name,
-        name,
-        path,
-        srcpath,
-        repository_ctx.attr,
-        _PASS_PROPS,
-        repository_ctx.attr.additional_rule_attrs,
+        name = name,
+        additional_rule_attrs = repository_ctx.attr.additional_rule_attrs,
+        attrs = repository_ctx.attr,
+        import_attr = repository_ctx.attr.rule_metadata["import_attr"],
+        path = path,
+        props = _PASS_PROPS,
+        rule_name = repository_ctx.attr.rule_name,
+        srcpath = srcpath,
     ))
     if (repository_ctx.attr.neverlink and
         repository_ctx.attr.generated_linkable_rule_name):
         lines.extend(_serialize_given_rule_import(
-            repository_ctx.attr.rule_name,
-            repository_ctx.attr.generated_linkable_rule_name,
-            path,
-            srcpath,
-            repository_ctx.attr,
-            [p for p in _PASS_PROPS if p != "neverlink"],
-            repository_ctx.attr.additional_rule_attrs,
+            name = repository_ctx.attr.generated_linkable_rule_name,
+            additonal_rule_attrs = repository_ctx.attr.additional_rule_attrs,
+            attrs = repository_ctx.attr,
+            import_attr = repository_ctx.attr.rule_metadata["import_attr"],
+            path = path,
+            props = [p for p in _PASS_PROPS if p != "neverlink"],
+            rule_name = repository_ctx.attr.rule_name,
+            srcpath = srcpath,
         ))
     extra = repository_ctx.attr.extra_build_file_content
     if extra:
@@ -103,7 +108,7 @@ def _jvm_import_external(repository_ctx):
     if srcurls:
         repository_ctx.download(srcurls, srcpath, srcsha)
     repository_ctx.file("BUILD", "\n".join(lines))
-    repository_ctx.file("jar/BUILD", "\n".join([
+    repository_ctx.file("%s/BUILD" % extension, "\n".join([
         _HEADER,
         "",
         "package(default_visibility = %r)" % (
@@ -112,18 +117,20 @@ def _jvm_import_external(repository_ctx):
         ),
         "",
         "alias(",
-        "    name = \"jar\",",
+        "    name = \"%s\"," % extension,
         "    actual = \"@%s\"," % repository_ctx.name,
         ")",
         "",
     ]))
 
-def _convert_to_url(artifact, server_urls):
+# This method is public for usage in android.bzl macros
+def convert_artifact_coordinate_to_urls(artifact, server_urls, packaging):
+    """This function converts a Maven artifact coordinate into URLs."""
+
     parts = artifact.split(":")
     group_id_part = parts[0].replace(".", "/")
     artifact_id = parts[1]
     version = parts[2]
-    packaging = "jar"
     classifier_part = ""
     if len(parts) == 4:
         packaging = parts[2]
@@ -146,12 +153,13 @@ def _concat_with_needed_slash(server_url, url_suffix):
     else:
         return server_url + "/" + url_suffix
 
-def _serialize_given_rule_import(rule_name, name, path, srcpath, attrs, props, additional_rule_attrs):
+def _serialize_given_rule_import(rule_name, import_attr, name, path, srcpath, attrs, props, additional_rule_attrs):
     lines = [
         "%s(" % rule_name,
         "    name = %s," % repr(name),
-        "    jars = [%s]," % repr(path),
+        "    " + import_attr % repr(path) + ",",
     ]
+
     if srcpath:
         lines.append("    srcjar = %s," % repr(srcpath))
     for prop in props:
@@ -167,12 +175,23 @@ def _serialize_given_rule_import(rule_name, name, path, srcpath, attrs, props, a
     return lines
 
 jvm_import_external = repository_rule(
-    implementation = _jvm_import_external,
     attrs = {
         "rule_name": attr.string(mandatory = True),
-        "licenses": attr.string_list(mandatory = True, allow_empty = False),
-        "jar_urls": attr.string_list(mandatory = True, allow_empty = False),
-        "jar_sha256": attr.string(),
+        "licenses": attr.string_list(
+            mandatory = True,
+            allow_empty = False,
+        ),
+        "artifact_urls": attr.string_list(
+            mandatory = True,
+            allow_empty = False,
+        ),
+        "artifact_sha256": attr.string(),
+        "rule_metadata": attr.string_dict(
+            default = {
+                "extension": "jar",
+                "import_attr": "jars = [%s]",
+            },
+        ),
         "rule_load": attr.string(),
         "additional_rule_attrs": attr.string_dict(),
         "srcjar_urls": attr.string_list(),
@@ -187,10 +206,15 @@ jvm_import_external = repository_rule(
         "default_visibility": attr.string_list(default = ["//visibility:public"]),
         "extra_build_file_content": attr.string(),
     },
+    implementation = _jvm_import_external,
 )
 
 def jvm_maven_import_external(artifact, server_urls, **kwargs):
     jvm_import_external(
-        jar_urls = _convert_to_url(artifact, server_urls),
+        artifact_urls = convert_artifact_coordinate_to_urls(
+            artifact,
+            server_urls,
+            "jar",
+        ),
         **kwargs
     )