Add subpath support to volumes with type volume in --mount option

To allow subpath mount as describes in [Compose Specs](https://github.com/compose-spec/compose-spec/blob/main/05-services.md),

Compose entries exemple:

    - type: volume
      source: webservices
      target: /srv/www/vhosts/server1
      read_only: true
      volume:
        subpath: server1
    - type: volume
      source: webservices
      target: /srv/www/vhosts/server2
      read_only: true
      volume:
        subpath: server2
    - type: volume
      source: webservices
      target: /srv/www/vhosts/server2/uploads
      read_only: false
      volume:
        subpath: server2/uploads

Runs podman with options

    --mount type=volume,source=webservices,target=/srv/www/vhosts/server1,ro
    --mount type=volume,source=webservices,target=/srv/www/vhosts/server2,ro,subpath=server2
    --mount type=volume,source=webservices,target=/srv/www/vhosts/server2/uploads,subpath=server2/uploads

Signed-off-by: fccagou <[email protected]>

Author: fccagou

podman_compose.py

@@ -478,11 +478,14 @@ def mount_desc_to_mount_args(mount_desc: dict[str, Any]) -> str:
         selinux = bind_opts.get("selinux")
         if selinux is not None:
             opts.append(selinux)
-    if mount_type == "image":
-        image_opts = mount_desc.get("image", {})
-        subpath = image_opts.get("subpath")
+
+    # According to compose specifications https://docs.docker.com/reference/compose-file/services/#volumes
+    # subpath can be used in image and volume mount type
+    if mount_type in ["volume", "image"] and mount_desc.get(mount_type):
+        subpath = mount_desc.get(mount_type, {}).get("subpath")
         if subpath is not None:
             opts.append(f"subpath={subpath}")
+
     opts_str = ",".join(opts)
     if mount_type == "bind":
         return f"type=bind,source={source},destination={target},{opts_str}".rstrip(",")
@@ -580,9 +583,13 @@ async def get_mount_args(
     volume = get_mnt_dict(compose, cnt, volume)
     srv_name = cnt["_service"]
     mount_type = volume["type"]
-    ignore_mount_type = {"image", "glob"}
+    # By default, mount using -v is actually preferred over --mount.
+    # In some case, options can only be set using --mount.
+    # --mount is forced for type set in mount_over_volume_needed var.
+    #
+    mount_over_volume_needed = {"image", "glob", "volume"}
     await assert_volume(compose, volume)
-    if compose.prefer_volume_over_mount and mount_type not in ignore_mount_type:
+    if compose.prefer_volume_over_mount and mount_type not in mount_over_volume_needed:
         if mount_type == "tmpfs":
             # TODO: --tmpfs /tmp:rw,size=787448k,mode=1777
             args = volume["target"]

tests/unit/test_container_to_args.py

@@ -756,6 +756,47 @@ async def test_volumes_image_mount(
             ],
         )
 
+    @parameterized.expand([
+        (
+            "without_subpath",
+            {},
+            "type=volume,source=volname,destination=/mnt/example",
+        ),
+        (
+            "with_subpath",
+            {"volume": {"subpath": "path/into/volume"}},
+            "type=volume,source=volname,destination=/mnt/example,subpath=path/into/volume",
+        ),
+    ])
+    async def test_volumes_mount(
+        self, test_name: str, volume_opts: dict, expected_mount_arg: str
+    ) -> None:
+        c = create_compose_mock()
+        cnt = get_minimal_container()
+        cnt["_service"] = cnt["service_name"]
+
+        cnt["volumes"] = [
+            {
+                "type": "volume",
+                "source": "volname",
+                "target": "/mnt/example",
+                **volume_opts,
+            },
+        ]
+
+        args = await container_to_args(c, cnt)
+        self.assertEqual(
+            args,
+            [
+                "--name=project_name_service_name1",
+                "-d",
+                "--mount",
+                expected_mount_arg,
+                "--network=bridge:alias=service_name",
+                "busybox",
+            ],
+        )
+
     @parameterized.expand([
         (
             "create_host_path_set_to_true",