Implement get_build_targets_impl in GeneralTestsOptimizer

Implement functionality in GeneralTestsOptimizer to find what targets to
build.

This logic is fairly complex and involves checking for test
configs that download general-tests.zip. Then the configs are checked to
see if they're proper test mapping tests (if they use the
'test-mapping-test-group' option). If they are, then TEST_MAPPING
modules are scanned to see if the list of changed files would cause any
test mapping modules to run. The tests are then further filtered by
test-mapping-test-groups used in the test configs.

In case that a test uses general-tests.zip but does not specify
'test-mapping-test-group' then all bets are off and general-tests.zip
is built in its entirety.

package_outputs is still unimplemented so this will need to be
implemented before the optimization can be enabled.

Test: atest build_test_suites_test && atest optimized_targets_test
Bug: 358215235
Change-Id: I6a7eebfd1b06b380799292eb2019ac17c9af5367

ci/optimized_targets.py

@@ -16,8 +16,13 @@
 from abc import ABC
 import argparse
 import functools
-from typing import Self
 from build_context import BuildContext
+import json
+import logging
+import os
+from typing import Self
+
+import test_mapping_module_retriever
 
 
 class OptimizedBuildTarget(ABC):
@@ -41,7 +46,10 @@ class OptimizedBuildTarget(ABC):
   def get_build_targets(self) -> set[str]:
     features = self.build_context.enabled_build_features
     if self.get_enabled_flag() in features:
-      return self.get_build_targets_impl()
+      self.modules_to_build = self.get_build_targets_impl()
+      return self.modules_to_build
+
+    self.modules_to_build = {self.target}
     return {self.target}
 
   def package_outputs(self):
@@ -82,6 +90,30 @@ class NullOptimizer(OptimizedBuildTarget):
     pass
 
 
+class ChangeInfo:
+
+  def __init__(self, change_info_file_path):
+    try:
+      with open(change_info_file_path) as change_info_file:
+        change_info_contents = json.load(change_info_file)
+    except json.decoder.JSONDecodeError:
+      logging.error(f'Failed to load CHANGE_INFO: {change_info_file_path}')
+      raise
+
+    self._change_info_contents = change_info_contents
+
+  def find_changed_files(self) -> set[str]:
+    changed_files = set()
+
+    for change in self._change_info_contents['changes']:
+      project_path = change.get('projectPath') + '/'
+
+      for revision in change.get('revisions'):
+        for file_info in revision.get('fileInfos'):
+          changed_files.add(project_path + file_info.get('path'))
+
+    return changed_files
+
 class GeneralTestsOptimizer(OptimizedBuildTarget):
   """general-tests optimizer
 
@@ -94,8 +126,55 @@ class GeneralTestsOptimizer(OptimizedBuildTarget):
   normally built.
   """
 
+  # List of modules that are always required to be in general-tests.zip.
+  _REQUIRED_MODULES = frozenset(
+      ['cts-tradefed', 'vts-tradefed', 'compatibility-host-util']
+  )
+
+  def get_build_targets_impl(self) -> set[str]:
+    change_info_file_path = os.environ.get('CHANGE_INFO')
+    if not change_info_file_path:
+      logging.info(
+          'No CHANGE_INFO env var found, general-tests optimization disabled.'
+      )
+      return {'general-tests'}
+
+    test_infos = self.build_context.test_infos
+    test_mapping_test_groups = set()
+    for test_info in test_infos:
+      is_test_mapping = test_info.is_test_mapping
+      current_test_mapping_test_groups = test_info.test_mapping_test_groups
+      uses_general_tests = test_info.build_target_used('general-tests')
+
+      if uses_general_tests and not is_test_mapping:
+        logging.info(
+            'Test uses general-tests.zip but is not test-mapping, general-tests'
+            ' optimization disabled.'
+        )
+        return {'general-tests'}
+
+      if is_test_mapping:
+        test_mapping_test_groups.update(current_test_mapping_test_groups)
+
+    change_info = ChangeInfo(change_info_file_path)
+    changed_files = change_info.find_changed_files()
+
+    test_mappings = test_mapping_module_retriever.GetTestMappings(
+        changed_files, set()
+    )
+
+    modules_to_build = set(self._REQUIRED_MODULES)
+
+    modules_to_build.update(
+        test_mapping_module_retriever.FindAffectedModules(
+            test_mappings, changed_files, test_mapping_test_groups
+        )
+    )
+
+    return modules_to_build
+
   def get_enabled_flag(self):
-    return 'general-tests-optimized'
+    return 'general_tests_optimized'
 
   @classmethod
   def get_optimized_targets(cls) -> dict[str, OptimizedBuildTarget]: