fix: prepare to generate grafeas (#2761)

In this PR:
- Add suffix to sample source folder
- Add unit tests

Context:
- The package name of grafeas is `io.grafeas.v1` which is not starts
with `com`. When copying samples to destination directory, we need to
change the suffix of source directory.
- grafeas doesn't have a valid api_id (empty string). Before this
change, the `api_id` will be populated as
`{library.api_shortname}.googleapis.com`, which is not correct. `api_id`
should not be populated to `.repo-metadata.json` if set to empty string.

With the library entry added in generation configuration:
```
- api_shortname: containeranalysis
  name_pretty: Grafeas
  product_documentation: https://grafeas.io
  api_description: n/a
  client_documentation: "https://cloud.google.com/java/docs/reference/grafeas/latest/overview"
  release_level: stable
  distribution_name: "io.grafeas:grafeas"
  api_id: ""
  codeowner_team: "@googleapis/aap-dpes"
  library_name: grafeas
  requires_billing: false
  GAPICs:
  - proto_path: grafeas/v1
 ```

The generated java-grafeas is in googleapis/google-cloud-java#10820

Author: JoeWang1127

library_generation/test/resources/test_mv_src/gapic/destination/java_gapic_srcjar/src/main/java/example_main.txt

@@ -102,6 +102,65 @@ def test_sh_util_nonexistent_function_fails(self):
         with self.assertRaises(RuntimeError):
             result = util.sh_util("nonexistent_function")
 
+    def test_mv_src_files_gapic_main_succeeds(self):
+        previous_dir = os.getcwd()
+        os.chdir(f"{resources_dir}/test_mv_src/gapic")
+        os.environ["folder_name"] = "example"
+        util.sh_util("mv_src_files gapic main destination")
+        self.assertTrue(
+            os.path.isfile("destination/gapic-example/src/main/java/example_main.txt")
+        )
+        shutil.rmtree("destination/gapic-example")
+        os.chdir(previous_dir)
+
+    def test_mv_src_files_gapic_test_succeeds(self):
+        previous_dir = os.getcwd()
+        os.chdir(f"{resources_dir}/test_mv_src/gapic")
+        os.environ["folder_name"] = "example"
+        util.sh_util("mv_src_files gapic test destination")
+        self.assertTrue(
+            os.path.isfile("destination/gapic-example/src/test/java/example_test.txt")
+        )
+        shutil.rmtree("destination/gapic-example")
+        os.chdir(previous_dir)
+
+    def test_mv_src_files_proto_main_succeeds(self):
+        previous_dir = os.getcwd()
+        os.chdir(f"{resources_dir}/test_mv_src/proto")
+        os.environ["folder_name"] = "example"
+        util.sh_util("mv_src_files proto main destination")
+        self.assertTrue(
+            os.path.isfile(
+                "destination/proto-example/src/main/java/example_proto_main.txt"
+            )
+        )
+        shutil.rmtree("destination/proto-example")
+        os.chdir(previous_dir)
+
+    def test_mv_src_files_sample_suffix_io_succeeds(self):
+        previous_dir = os.getcwd()
+        os.chdir(f"{resources_dir}/test_mv_src/samples")
+        util.sh_util("mv_src_files samples main destination_io")
+        self.assertTrue(
+            os.path.isfile(
+                "destination_io/samples/snippets/generated/io/example_io_sample.txt"
+            )
+        )
+        shutil.rmtree("destination_io/samples")
+        os.chdir(previous_dir)
+
+    def test_mv_src_files_sample_suffix_com_succeeds(self):
+        previous_dir = os.getcwd()
+        os.chdir(f"{resources_dir}/test_mv_src/samples")
+        util.sh_util("mv_src_files samples main destination_com")
+        self.assertTrue(
+            os.path.isfile(
+                "destination_com/samples/snippets/generated/com/example_com_sample.txt"
+            )
+        )
+        shutil.rmtree("destination_com/samples")
+        os.chdir(previous_dir)
+
     def test_eprint_valid_input_succeeds(self):
         test_input = "This is some test input"
         # create a stdio capture object
@@ -247,7 +306,7 @@ def test_gapic_inputs_parse_no_service_yaml_returns_empty_string(self):
 
     def test_generate_prerequisite_files_non_monorepo_success(self):
         library_path = self.__setup_prerequisite_files(
-            num_libraries=1, library_type="GAPIC_COMBO"
+            combination=1, library_type="GAPIC_COMBO"
         )
 
         file_comparator.compare_files(
@@ -266,7 +325,7 @@ def test_generate_prerequisite_files_non_monorepo_success(self):
         self.__remove_prerequisite_files(path=library_path, is_monorepo=False)
 
     def test_generate_prerequisite_files_monorepo_success(self):
-        library_path = self.__setup_prerequisite_files(num_libraries=2)
+        library_path = self.__setup_prerequisite_files(combination=2)
 
         file_comparator.compare_files(
             f"{library_path}/.repo-metadata.json",
@@ -317,7 +376,10 @@ def test_prepare_repo_split_repo_success(self):
         shutil.rmtree(repo_config.output_folder)
 
     def __setup_prerequisite_files(
-        self, num_libraries: int, library_type: str = "GAPIC_AUTO"
+        self,
+        combination: int,
+        library_type: str = "GAPIC_AUTO",
+        library: LibraryConfig = library_1,
     ) -> str:
         library_path = f"{resources_dir}/goldens"
         files = [
@@ -326,12 +388,12 @@ def __setup_prerequisite_files(
             f"{library_path}/owlbot.py",
         ]
         cleanup(files)
-        config = self.__get_a_gen_config(num_libraries, library_type=library_type)
+        config = self.__get_a_gen_config(combination, library_type=library_type)
         proto_path = "google/cloud/baremetalsolution/v2"
         transport = "grpc"
         util.generate_prerequisite_files(
             config=config,
-            library=library_1,
+            library=library,
             proto_path=proto_path,
             transport=transport,
             library_path=library_path,
@@ -340,28 +402,28 @@ def __setup_prerequisite_files(
 
     @staticmethod
     def __get_a_gen_config(
-        num_libraries: int, library_type: str = "GAPIC_AUTO"
+        combination: int, library_type: str = "GAPIC_AUTO"
     ) -> GenerationConfig:
         """
         Returns an object of GenerationConfig with one to three of
         LibraryConfig objects. Other attributes are set to empty str.
 
-        :param num_libraries: the number of LibraryConfig objects associated with
+        :param combination: combination of LibraryConfig objects associated with
         the GenerationConfig. Only support 1, 2 or 3.
         :return: an object of GenerationConfig
         """
-        if num_libraries == 2:
+        if combination == 2:
             libraries = [library_1, library_2]
-        elif num_libraries == 3:
-            libraries = [library_1, library_2, library_3]
+        elif combination == 3:
+            libraries = [library_with_empty_api_id, library_2]
         else:
             libraries = [library_1]
 
         # update libraries with custom configuration (for now, only
         # library_type)
         for library in libraries:
             library.library_type = library_type
-            if num_libraries == 1:
+            if combination == 1:
                 # treat this as a HW library case to generate a real-life
                 # repo-metadata
                 library.extra_versioned_modules = "test-module"

library_generation/test/resources/test_mv_src/gapic/destination/java_gapic_srcjar/src/test/java/example_test.txt

@@ -32,20 +32,25 @@ mv_src_files() {
   local type=$2 # one of main, test
   local destination_path=$3
   if [ "${category}" == "samples" ]; then
-    src_suffix="samples/snippets/generated/src/main/java/com"
+    src_suffix="samples/snippets/generated/src/main/java"
     folder_suffix="samples/snippets/generated"
+    mkdir -p "${destination_path}/${folder_suffix}"
+    cp -r "${destination_path}/java_gapic_srcjar/${src_suffix}"/* "${destination_path}/${folder_suffix}"
   elif [ "${category}" == "proto" ]; then
     src_suffix="${category}/src/${type}/java"
     folder_suffix="${category}-${folder_name}/src/${type}"
   else
     src_suffix="src/${type}"
     folder_suffix="${category}-${folder_name}/src"
   fi
+
+  if [ "${category}" == "samples" ]; then
+    return
+  fi
+
   mkdir -p "${destination_path}/${folder_suffix}"
   cp -r "${destination_path}/java_gapic_srcjar/${src_suffix}" "${destination_path}/${folder_suffix}"
-  if [ "${category}" != "samples" ]; then
-    rm -r -f "${destination_path}/${folder_suffix}/java/META-INF"
-  fi
+  rm -r -f "${destination_path}/${folder_suffix}/java/META-INF"
 }
 
 # unzip jar file