fix: Add error handling for provided runtime layer building (#5733)

* fix: Add error handling for provided runtime layer building

* Format

* Default to runtime language instead of throwing an exception

* Add integration tests

* Fix template spacing

samcli/lib/build/app_builder.py

@@ -62,6 +62,8 @@
 
 LOG = logging.getLogger(__name__)
 
+FIRST_COMPATIBLE_RUNTIME_INDEX = 0
+
 
 class ApplicationBuildResult(NamedTuple):
     """
@@ -546,7 +548,9 @@ def _build_layer(
                     )
                     # Only set to this value if specified workflow is makefile
                     # which will result in config language as provided
-                    build_runtime = compatible_runtimes[0]
+                    build_runtime = (
+                        compatible_runtimes[FIRST_COMPATIBLE_RUNTIME_INDEX] if compatible_runtimes else config.language
+                    )
                 global_image = self._build_images.get(None)
                 image = self._build_images.get(layer_name, global_image)
                 # pass to container only when specified workflow is supported to overwrite runtime to get image

tests/integration/buildcmd/test_build_cmd.py

@@ -1753,6 +1753,8 @@ class TestBuildCommand_LayerBuilds(BuildIntegBase):
     EXPECTED_FILES_PROJECT_MANIFEST = {"__init__.py", "main.py", "requirements.txt"}
     EXPECTED_LAYERS_FILES_PROJECT_MANIFEST = {"__init__.py", "layer.py", "numpy", "requirements.txt"}
 
+    EXPECTED_LAYERS_FILES_NO_COMPATIBLE_RUNTIMES = {"__init__.py", "layer.py", "requirements.txt"}
+
     @parameterized.expand(
         [
             ("python3.7", False, "LayerOne", "ContentUri"),
@@ -1810,6 +1812,31 @@ def test_build_layer_with_makefile(self, build_method, use_container, layer_iden
             "python",
         )
 
+    @skipIf(SKIP_DOCKER_TESTS or SKIP_DOCKER_BUILD, SKIP_DOCKER_MESSAGE)
+    def test_build_layer_with_makefile_no_compatible_runtimes(self):
+        build_method = "makefile"
+        use_container = True
+        layer_identifier = "LayerWithMakefileNoCompatibleRuntimes"
+
+        overrides = {"LayerBuildMethod": build_method, "LayerMakeContentUri": "PyLayerMake"}
+        cmdlist = self.get_command_list(
+            use_container=use_container, parameter_overrides=overrides, function_identifier=layer_identifier
+        )
+
+        LOG.info("Running Command: {}".format(cmdlist))
+
+        command_result = run_command(cmdlist, cwd=self.working_dir)
+        self.assertEqual(command_result.process.returncode, 0)
+
+        LOG.info("Default build dir: %s", self.default_build_dir)
+        self._verify_built_artifact(
+            self.default_build_dir,
+            layer_identifier,
+            self.EXPECTED_LAYERS_FILES_NO_COMPATIBLE_RUNTIMES,
+            "ContentUri",
+            "random",
+        )
+
     @parameterized.expand([("python3.7", False, "LayerTwo"), ("python3.7", "use_container", "LayerTwo")])
     def test_build_fails_with_missing_metadata(self, runtime, use_container, layer_identifier):
         if use_container and (SKIP_DOCKER_TESTS or SKIP_DOCKER_BUILD):

tests/integration/testdata/buildcmd/PyLayerMake/Makefile

@@ -3,3 +3,8 @@ build-LayerWithMakefile:
 	cp *.py "$(ARTIFACTS_DIR)/python"
 	cp *.txt "$(ARTIFACTS_DIR)/python"
 	python -m pip install -r requirements.txt -t "$(ARTIFACTS_DIR)/python"
+build-LayerWithMakefileNoCompatibleRuntimes:
+	mkdir -p "$(ARTIFACTS_DIR)/random"
+	cp *.py "$(ARTIFACTS_DIR)/random"
+	cp *.txt "$(ARTIFACTS_DIR)/random"
+

tests/integration/testdata/buildcmd/layers-functions-template.yaml

@@ -64,3 +64,11 @@ Resources:
         - python3.7
     Metadata:
       BuildMethod: !Ref LayerBuildMethod
+
+  LayerWithMakefileNoCompatibleRuntimes:
+    Type: AWS::Serverless::LayerVersion
+    Properties:
+      Description: Layer four
+      ContentUri: !Ref LayerMakeContentUri
+    Metadata:
+      BuildMethod: !Ref LayerBuildMethod

tests/unit/lib/build_module/test_app_builder.py

@@ -571,6 +571,43 @@ def test_must_build_layer_in_process(self, get_layer_subfolder_mock, osutils_moc
             is_building_layer=True,
         )
 
+    @parameterized.expand([([],), (None,)])
+    @patch("samcli.lib.build.app_builder.get_workflow_config")
+    @patch("samcli.lib.build.app_builder.osutils")
+    @patch("samcli.lib.build.app_builder.get_layer_subfolder")
+    def test_must_handle_layer_build_compatible_runtimes_missing(
+        self, compatible_runtimes, get_layer_subfolder_mock, osutils_mock, get_workflow_config_mock
+    ):
+        get_layer_subfolder_mock.return_value = "layer"
+        config_mock = Mock()
+        config_mock.manifest_name = "manifest_name"
+        config_mock.language = "provided"
+
+        scratch_dir = "scratch"
+        osutils_mock.mkdir_temp.return_value.__enter__ = Mock(return_value=scratch_dir)
+        osutils_mock.mkdir_temp.return_value.__exit__ = Mock()
+
+        get_workflow_config_mock.return_value = config_mock
+        build_function_on_container_mock = Mock()
+
+        self.builder._container_manager = Mock()
+        self.builder._build_function_on_container = build_function_on_container_mock
+        self.builder._build_layer("layer_name", "code_uri", "provided", compatible_runtimes, ARM64, "full_path")
+
+        build_function_on_container_mock.assert_called_once_with(
+            config_mock,
+            PathValidator("code_uri"),
+            PathValidator("layer"),
+            PathValidator("manifest_name"),
+            "provided",
+            ARM64,
+            {"build_logical_id": "layer_name"},
+            None,
+            None,
+            is_building_layer=True,
+            specified_workflow=None,
+        )
+
     @patch("samcli.lib.build.app_builder.get_workflow_config")
     @patch("samcli.lib.build.app_builder.osutils")
     @patch("samcli.lib.build.app_builder.get_layer_subfolder")