Pass build description labels to podman build

The Compose Specification supports adding labels to the build image
which is also used in practice. Support this and pass the labels to
`podman build`.

Signed-off-by: Sebastian Wick <sebastian.wick@redhat.com>

podman_compose.py

@@ -2378,6 +2378,11 @@ async def build_one(compose, args, cnt):
         build_args.extend(get_secret_args(compose, cnt, secret, podman_is_building=True))
     for tag in build_desc.get("tags", []):
         build_args.extend(["-t", tag])
+    labels = build_desc.get("labels", [])
+    if isinstance(labels, dict):
+        labels = [f"{k}={v}" for (k, v) in labels.items()]
+    for label in labels:
+        build_args.extend(["--label", label])
     for additional_ctx in build_desc.get("additional_contexts", {}):
         build_args.extend([f"--build-context={additional_ctx}"])
     if "target" in build_desc:

tests/integration/build/README.md

@@ -21,5 +21,3 @@ ALT buildno=2 port 8000 2019-09-03T15:16:38+0000
 
 as you can see we were able to override buildno to be 2 instead of 1,
 and httpd_port to 8000.
-
-NOTE: build labels are not passed to `podman build`

tests/integration/build_labels/context/Dockerfile

@@ -0,0 +1 @@
+FROM busybox

tests/integration/build_labels/docker-compose.yml

@@ -0,0 +1,22 @@
+version: "3"
+services:
+  test_build_labels_map:
+    build:
+      context: ./context
+      dockerfile: Dockerfile
+      labels:
+        com.example.description: "Accounting webapp"
+        com.example.department: "Finance"
+        com.example.label-with-empty-value: ""
+    image: my-busybox-build-labels-map
+    command: env
+  test_build_labels_array:
+    build:
+      context: ./context
+      dockerfile: Dockerfile
+      labels:
+        - "com.example.description=Accounting webapp"
+        - "com.example.department=Finance"
+        - "com.example.label-with-empty-value"
+    image: my-busybox-build-labels-array
+    command: env

tests/integration/build_labels/test_build_labels.py

@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: GPL-2.0
+
+
+import json
+import os
+import unittest
+
+from tests.integration.test_podman_compose import podman_compose_path
+from tests.integration.test_podman_compose import test_path
+from tests.integration.test_utils import RunSubprocessMixin
+
+
+class TestBuildLabels(unittest.TestCase, RunSubprocessMixin):
+    def test_build_labels(self):
+        """The build context can contain labels which should be added to the resulting image. They
+        can be either an array or a map.
+        """
+
+        compose_path = os.path.join(test_path(), "build_labels/docker-compose.yml")
+
+        try:
+            self.run_subprocess_assert_returncode([
+                podman_compose_path(),
+                "-f",
+                compose_path,
+                "build",
+                "test_build_labels_map",
+                "test_build_labels_array",
+            ])
+
+            expected_labels = {
+                "com.example.department": "Finance",
+                "com.example.description": "Accounting webapp",
+                "com.example.label-with-empty-value": "",
+            }
+
+            out, _ = self.run_subprocess_assert_returncode([
+                "podman",
+                "inspect",
+                "my-busybox-build-labels-map",
+                "my-busybox-build-labels-array",
+            ])
+
+            images = json.loads(out)
+            self.assertEqual(len(images), 2)
+            labels_map = images[0].get("Config", {}).get("Labels", {})
+            labels_array = images[1].get("Config", {}).get("Labels", {})
+            for k, v in expected_labels.items():
+                self.assertIn(k, labels_map)
+                self.assertEqual(labels_map[k], v)
+                self.assertIn(k, labels_array)
+                self.assertEqual(labels_array[k], v)
+
+        finally:
+            self.run_subprocess_assert_returncode([
+                "podman",
+                "rmi",
+                "my-busybox-build-labels-map",
+                "my-busybox-build-labels-array",
+            ])