feat: parse BUILD.bzel to determine whether a commit that only chan…

…ged `BUILD.bazel` is a qualified commit (#2937)

In this PR:
- For a commit that only changed `BUILD.bzel`, parse the `BUILD.bazel`
to determine whether this is a qualified commit. The commit is a
qualified commit if the two `Gapic_Inputs` objects parsed from the
commit and its parent are different.

library_generation/model/config_change.py

@@ -16,11 +16,16 @@
 from enum import Enum
 from typing import Optional
 from git import Commit, Repo
+
+from library_generation.model.gapic_inputs import parse_build_str
 from library_generation.model.generation_config import GenerationConfig
 from library_generation.model.library_config import LibraryConfig
 from library_generation.utils.utilities import sh_util
 from library_generation.utils.proto_path_utils import find_versioned_proto_path
 
+INSERTIONS = "insertions"
+LINES = "lines"
+
 
 class ChangeType(Enum):
     GOOGLEAPIS_COMMIT = 1
@@ -77,6 +82,7 @@ def get_changed_libraries(self) -> Optional[list[str]]:
         Returns a unique, sorted list of library name of changed libraries.
         None if there is a repository level change, which means all libraries
         in the current_config will be generated.
+
         :return: library names of change libraries.
         """
         if ChangeType.REPO_LEVEL_CHANGE in self.change_to_libraries:
@@ -143,11 +149,23 @@ def __create_qualified_commit(
         :return: qualified commits.
         """
         libraries = set()
-        for file in commit.stats.files.keys():
-            if file.endswith("BUILD.bazel"):
-                continue
-            versioned_proto_path = find_versioned_proto_path(file)
+        for file_path, changes in commit.stats.files.items():
+            versioned_proto_path = find_versioned_proto_path(file_path)
             if versioned_proto_path in proto_paths:
+                if (
+                    file_path.endswith("BUILD.bazel")
+                    # Qualify a commit if the commit only added BUILD.bazel
+                    # because it's very unlikely that a commit added BUILD.bazel
+                    # without adding proto files. Therefore, the commit is
+                    # qualified duo to the proto change eventually.
+                    and (not ConfigChange.__is_added(changes))
+                    and (
+                        not ConfigChange.__is_qualified_build_change(
+                            commit=commit, build_file_path=file_path
+                        )
+                    )
+                ):
+                    continue
                 # Even though a commit usually only changes one
                 # library, we don't want to miss generating a
                 # library because the commit may change multiple
@@ -156,3 +174,30 @@ def __create_qualified_commit(
         if len(libraries) == 0:
             return None
         return QualifiedCommit(commit=commit, libraries=libraries)
+
+    @staticmethod
+    def __is_added(changes: dict[str, int]) -> bool:
+        return changes[INSERTIONS] == changes[LINES]
+
+    @staticmethod
+    def __is_qualified_build_change(commit: Commit, build_file_path: str) -> bool:
+        """
+        Checks if the given commit containing a BUILD.bazel change is a
+        qualified commit.
+
+        The commit is a qualified commit if the
+        :class:`library_generation.model.gapic_inputs.GapicInputs` objects
+        parsed from the commit and its parent are different, since there are
+        changes in fields that used in library generation.
+
+        :param commit: a GitHub commit object.
+        :param build_file_path: the path of the BUILD.bazel
+        :return: True if the commit is a qualified commit; False otherwise.
+        """
+        versioned_proto_path = find_versioned_proto_path(build_file_path)
+        build = str((commit.tree / build_file_path).data_stream.read())
+        parent_commit = commit.parents[0]
+        parent_build = str((parent_commit.tree / build_file_path).data_stream.read())
+        inputs = parse_build_str(build, versioned_proto_path)
+        parent_inputs = parse_build_str(parent_build, versioned_proto_path)
+        return inputs != parent_inputs

library_generation/model/gapic_inputs.py

@@ -72,6 +72,20 @@ def __init__(
         self.service_yaml = service_yaml
         self.include_samples = include_samples
 
+    def __eq__(self, other):
+        if not isinstance(other, GapicInputs):
+            return False
+        return (
+            self.proto_only == other.proto_only
+            and self.additional_protos == other.additional_protos
+            and self.transport == other.transport
+            and self.rest_numeric_enum == other.rest_numeric_enum
+            and self.gapic_yaml == other.gapic_yaml
+            and self.service_config == other.service_config
+            and self.service_yaml == other.service_yaml
+            and self.include_samples == other.include_samples
+        )
+
 
 def parse(
     build_path: Path, versioned_path: str, build_file_name: str = "BUILD.bazel"
@@ -86,16 +100,19 @@ def parse(
     """
     with open(f"{build_path}/{build_file_name}") as build:
         content = build.read()
+    return parse_build_str(build_str=content, versioned_path=versioned_path)
+
 
+def parse_build_str(build_str: str, versioned_path: str) -> GapicInputs:
     proto_library_target = re.compile(
         proto_library_pattern, re.DOTALL | re.VERBOSE
-    ).findall(content)
+    ).findall(build_str)
     additional_protos = ""
     if len(proto_library_target) > 0:
         additional_protos = __parse_additional_protos(proto_library_target[0])
-    gapic_target = re.compile(gapic_pattern, re.DOTALL | re.VERBOSE).findall(content)
+    gapic_target = re.compile(gapic_pattern, re.DOTALL | re.VERBOSE).findall(build_str)
     assembly_target = re.compile(assembly_pattern, re.DOTALL | re.VERBOSE).findall(
-        content
+        build_str
     )
     include_samples = "false"
     if len(assembly_target) > 0:

library_generation/test/model/config_change_unit_tests.py

@@ -208,7 +208,34 @@ def test_get_qualified_commits_success(self):
             qualified_commits[2].commit.hexsha,
         )
 
-    def test_get_qualified_commits_build_only_commit_returns_empty_list(self):
+    def test_get_qualified_commits_rest_numeric_enum_change_returns_a_qualified_commit(
+        self,
+    ):
+        baseline_commit = "45694d2bad602c52170096072d325aa644d550e5"
+        latest_commit = "758f0d1217d9c7fe398aa5efb1057ce4b6409e55"
+        config_change = ConfigChange(
+            change_to_libraries={},
+            baseline_config=ConfigChangeTest.__get_a_gen_config(
+                googleapis_commitish=baseline_commit
+            ),
+            current_config=ConfigChangeTest.__get_a_gen_config(
+                googleapis_commitish=latest_commit,
+                libraries=[
+                    ConfigChangeTest.__get_a_library_config(
+                        library_name="container",
+                        gapic_configs=[GapicConfig(proto_path="google/container/v1")],
+                    )
+                ],
+            ),
+        )
+        # one commit between latest_commit and baseline_commit which only
+        # changed BUILD.bazel.
+        # this commit changed `rest_numeric_enums`.
+        self.assertTrue(len(config_change.get_qualified_commits()) == 1)
+
+    def test_get_qualified_commits_irrelevant_build_field_change_returns_empty_list(
+        self,
+    ):
         baseline_commit = "bdda0174f68a738518ec311e05e6fd9bbe19cd78"
         latest_commit = "c9a5050ef225b0011603e1109cf53ab1de0a8e53"
         config_change = ConfigChange(
@@ -228,8 +255,35 @@ def test_get_qualified_commits_build_only_commit_returns_empty_list(self):
         )
         # one commit between latest_commit and baseline_commit which only
         # changed BUILD.bazel.
+        # this commit didn't change fields used in library generation.
         self.assertTrue(len(config_change.get_qualified_commits()) == 0)
 
+    def test_get_qualified_commits_add_build_file_returns_a_qualified_commit(self):
+        baseline_commit = "d007ca1b3cc820651530d44d5388533047ae1414"
+        latest_commit = "05d889e7dfe087fc2ddc9de9579f01d4e1c2f35e"
+        config_change = ConfigChange(
+            change_to_libraries={},
+            baseline_config=ConfigChangeTest.__get_a_gen_config(
+                googleapis_commitish=baseline_commit
+            ),
+            current_config=ConfigChangeTest.__get_a_gen_config(
+                googleapis_commitish=latest_commit,
+                libraries=[
+                    ConfigChangeTest.__get_a_library_config(
+                        library_name="cloudcontrolspartner",
+                        gapic_configs=[
+                            GapicConfig(
+                                proto_path="google/cloud/cloudcontrolspartner/v1"
+                            )
+                        ],
+                    )
+                ],
+            ),
+        )
+        # one commit between latest_commit and baseline_commit which added
+        # google/cloud/cloudcontrolspartner/v1.
+        self.assertTrue(len(config_change.get_qualified_commits()) == 1)
+
     @staticmethod
     def __get_a_gen_config(
         googleapis_commitish="", libraries: list[LibraryConfig] = None