Merge <uses-library> dependency configs into dexpreopt.config files.

Since Make does not visit modules in topological order of their
<uses-library> dependencies, information from dependencies to the
dexpreopted module has to be passed via dexpreopt.config files. A build
rule for a dexpreopt.config file depends on dexpreopt.config files for
<uses-library> dependencies, and dex_preopt_config_merger.py script
extracts the necessary information from dependency configs and patches
the module's config.

Bug: 132357300
Test: lunch aosp_cf_x86_phone-userdebug && m
Change-Id: Id0b71170a4d2ab1d33059de0e9ad9d7e61f2345e

core/dex_preopt_config_merger.py

@@ -0,0 +1,100 @@
+#!/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 for merging dexpreopt.config files for <uses-library> dependencies into
+the dexpreopt.config file of the library/app that uses them. This is needed to
+generate class loader context (CLC) for dexpreopt.
+
+In Make there is no topological order when processing different modules, so a
+<uses-library> dependency module may have not been processed yet by the time the
+dependent module is processed. Therefore makefiles communicate the information
+from dependencies via dexpreopt.config files and add file-level dependencies
+from a module dexpreopt.config to its dependency configs. The actual patching
+of configs is done by this script, which is called from the makefiles.
+"""
+
+from __future__ import print_function
+
+import json
+from collections import OrderedDict
+import sys
+
+
+def main():
+  """Program entry point."""
+  if len(sys.argv) < 2:
+    raise SystemExit('usage: %s <main-config> [dep-config ...]' % sys.argv[0])
+
+  # Read all JSON configs.
+  cfgs = []
+  for arg in sys.argv[1:]:
+    with open(arg, 'r') as f:
+      cfgs.append(json.load(f, object_pairs_hook=OrderedDict))
+
+  # The first config is the dexpreopted library/app, the rest are its
+  # <uses-library> dependencies.
+  cfg0 = cfgs[0]
+
+  # Put dependency configs in a map keyed on module name (for easier lookup).
+  uses_libs = {}
+  for cfg in cfgs[1:]:
+    uses_libs[cfg['Name']] = cfg
+
+  # Load the original CLC map.
+  clc_map = cfg0['ClassLoaderContexts']
+
+  # Create a new CLC map that will be a copy of the original one with patched
+  # fields from dependency dexpreopt.config files.
+  clc_map2 = OrderedDict()
+
+  # Patch CLC for each SDK version. Although this should not be necessary for
+  # compatibility libraries (so-called "conditional CLC"), because they all have
+  # known names, known paths in system/framework, and no subcontext. But keep
+  # the loop in case this changes in the future.
+  for sdk_ver in clc_map:
+    clcs = clc_map[sdk_ver]
+    clcs2 = OrderedDict()
+    for lib in clcs:
+      clc = clcs[lib]
+      if lib in uses_libs:
+        ulib = uses_libs[lib]
+        # On-host (build) path to the dependency DEX jar file.
+        clc['Host'] = ulib['BuildPath']
+        # On-device (install) path to the dependency DEX jar file.
+        clc['Device'] = ulib['DexLocation']
+        # CLC of the dependency becomes a subcontext. We only need sub-CLC for
+        # 'any' version because all other versions are for compatibility
+        # libraries, which exist only for apps and not for libraries.
+        clc['Subcontexts'] = ulib['ClassLoaderContexts'].get('any')
+        # Patch the library name in the CLC as well.
+        clcs2[ulib['ProvidesUsesLibrary']] = clc
+      else:
+        # dexpreopt.config for this <uses-library> is not among the script
+        # arguments, which may be the case with compatibility libraries that
+        # don't need patching anyway. Just use the original CLC.
+        clcs2[lib] = clc
+    clc_map2[sdk_ver] = clcs2
+
+  # Overwrite the original class loader context with the patched one.
+  cfg0['ClassLoaderContexts'] = clc_map2
+
+  # Update dexpreopt.config file.
+  with open(sys.argv[1], 'w') as f:
+    f.write(json.dumps(cfgs[0], indent=4, separators=(',', ': ')))
+
+if __name__ == '__main__':
+  main()