Move Missing BuildArchitecture warning to build_layer

samcli/lib/build/app_builder.py

@@ -502,6 +502,13 @@ def _build_layer(
         str
             Path to the location where built artifacts are available
         """
+
+        if layer_metadata and "BuildArchitecture" not in layer_metadata:
+            LOG.warning(
+                "WARNING: No BuildArchitecture specifed in Layer `%s`" + " Metadata. Defaulting to x86_64.",
+                layer_name,
+            )
+
         # Create the arguments to pass to the builder
         # Code is always relative to the given base directory.
         code_dir = str(pathlib.Path(self._base_dir, codeuri).resolve())

samcli/lib/providers/provider.py

@@ -244,12 +244,6 @@ def __init__(
         self._compatible_runtimes = compatible_runtimes
         self._custom_layer_id = metadata.get(SAM_RESOURCE_ID_KEY)
 
-        if "BuildArchitecture" not in metadata:
-            LOG.warning(
-                "WARNING: No BuildArchitecture specifed in Layer `%s`" + " Metadata. Defaulting to x86_64.",
-                self._custom_layer_id,
-            )
-
         self._build_architecture = cast(str, metadata.get("BuildArchitecture", X86_64))
         self._compatible_architectures = compatible_architectures
 

tests/integration/buildcmd/test_build_cmd.py

@@ -1736,6 +1736,16 @@ def test_build_fails_with_missing_metadata(self, runtime, use_container, layer_i
         self.assertEqual(command_result.process.returncode, 1)
         self.assertFalse(self.default_build_dir.joinpath(layer_identifier).exists())
 
+    def test_function_build_succeeds_with_referenced_layer(self):
+        overrides = {"Runtime": "python3.8"}
+        cmdlist = self.get_command_list(
+            use_container=False, parameter_overrides=overrides, function_identifier="FunctionTwo"
+        )
+
+        command_result = run_command(cmdlist, cwd=self.working_dir)
+        self.assertEqual(command_result.process.returncode, 0)
+        self.assertNotIn("No BuildArchitecture specifed", str(command_result.stderr))
+
     @parameterized.expand([("python3.7", False, "LayerOne"), ("python3.7", "use_container", "LayerOne")])
     def test_build_with_missing_buildarchitecture(self, runtime, use_container, layer_identifier):
         if use_container and (SKIP_DOCKER_TESTS or SKIP_DOCKER_BUILD):

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

@@ -32,6 +32,16 @@ Resources:
       Layers:
         - !Ref LayerOne
 
+  FunctionTwo:
+    Type: AWS::Serverless::Function
+    Properties:
+      Handler: !Ref Handler
+      Runtime: !Ref Runtime
+      CodeUri: !Ref CodeUri
+      Timeout: 600
+      Layers:
+        - !Sub arn:${AWS::Partition}:lambda:${AWS::Region}:012345678912:layer:layerName:1
+
   LayerOne:
     Type: AWS::Serverless::LayerVersion
     Properties: