[scripts] Add script to print clang prebuilts version

Bug: http://b/187231324

This script parses soong/cc/config/global.go to return clang prebuilts
version.  (It may get the version from a json config file in the
future.)

Currently it's used in development/scripts/symbol.py and is the
recommended way to get clang prebuilts version number in the future.

Test: get_clang_version_test.py
Change-Id: Id92a74fd523a5270999bb4d6454525bf2f2f0c04

Android.bp

@@ -116,3 +116,13 @@ cc_genrule {
 dex_bootjars {
     name: "dex_bootjars",
 }
+
+// Pseudo-test that's run on checkbuilds to ensure that get_clang_version can
+// parse cc/config/global.go.
+genrule {
+    name: "get_clang_version_test",
+    cmd: "$(location get_clang_version) > $(out)",
+    tools: ["get_clang_version"],
+    srcs: ["cc/config/global.go"],
+    out: ["clang-prebuilts-version.txt"],
+}

scripts/Android.bp

@@ -265,3 +265,19 @@ python_binary_host {
         "linker_config_proto",
     ],
 }
+
+python_binary_host {
+    name: "get_clang_version",
+    main: "get_clang_version.py",
+    srcs: [
+        "get_clang_version.py",
+    ],
+    version: {
+        py2: {
+            enabled: false,
+        },
+        py3: {
+            enabled: true,
+        },
+    },
+}

scripts/get_clang_version.py

@@ -0,0 +1,46 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2021 The Android Open Source Project
+#
+# 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.
+"""A tool to report the current clang version used during build"""
+
+import os
+import re
+import sys
+
+
+ANDROID_BUILD_TOP = os.environ.get("ANDROID_BUILD_TOP", ".")
+
+def get_clang_prebuilts_version(global_go):
+  # TODO(b/187231324): Get clang version from the json file once it is no longer
+  # hard-coded in global.go
+  if global_go is None:
+      global_go = ANDROID_BUILD_TOP + '/build/soong/cc/config/global.go'
+  with open(global_go) as infile:
+    contents = infile.read()
+
+  regex_rev = r'\tClangDefaultVersion\s+= "clang-(?P<rev>r\d+[a-z]?\d?)"'
+  match_rev = re.search(regex_rev, contents)
+  if match_rev is None:
+    raise RuntimeError('Parsing clang info failed')
+  return match_rev.group('rev')
+
+
+def main():
+  global_go = sys.argv[1] if len(sys.argv) > 1 else None
+  print(get_clang_prebuilts_version(global_go));
+
+
+if __name__ == '__main__':
+  main()

scripts/get_clang_version_test.py

@@ -0,0 +1,32 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2021 The Android Open Source Project
+#
+# 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.
+#
+"""Unit tests for get_clang_version.py."""
+
+import unittest
+
+import get_clang_version
+
+class GetClangVersionTest(unittest.TestCase):
+  """Unit tests for get_clang_version."""
+
+  def test_get_clang_version(self):
+    """Test parsing of clang prebuilts version."""
+    self.assertIsNotNone(get_clang_version.get_clang_prebuilts_version())
+
+
+if __name__ == '__main__':
+  unittest.main(verbosity=2)