feat(meta): generate metadata for components

snapcraft/meta/component_yaml.py

@@ -0,0 +1,108 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright 2024 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Model and utilities for component.yaml metadata."""
+
+from pathlib import Path
+from typing import Any, Dict, Optional
+
+import yaml
+from pydantic import Extra
+from pydantic_yaml import YamlModel
+
+from snapcraft.errors import SnapcraftError
+from snapcraft.projects import Project
+
+
+class ComponentMetadata(YamlModel):
+    """The component.yaml model."""
+
+    component: str
+    type: str
+    version: Optional[str]
+    summary: str
+    description: str
+
+    class Config:  # pylint: disable=too-few-public-methods
+        """Pydantic model configuration."""
+
+        allow_population_by_field_name = True
+        alias_generator = lambda s: s.replace("_", "-")  # noqa: E731
+        extra = Extra.forbid
+
+    @classmethod
+    def unmarshal(cls, data: Dict[str, Any]) -> "ComponentMetadata":
+        """Create and populate a new ``ComponentMetadata`` object from dictionary data.
+
+        The unmarshal method validates entries in the input dictionary, populating
+        the corresponding fields in the data object.
+
+        :param data: The dictionary data to unmarshal.
+
+        :return: The newly created object.
+
+        :raise TypeError: If data is not a dictionary.
+        """
+        if not isinstance(data, dict):
+            raise TypeError("data is not a dictionary")
+
+        return cls(**data)
+
+
+def write(project: Project, component_name: str, component_prime_dir: Path) -> None:
+    """Create a component.yaml file.
+
+    :param project: The snapcraft project.
+    :param component_name: Name of the component.
+    :param component_prime_dir: The directory containing the component's primed contents.
+    """
+    meta_dir = component_prime_dir / "meta"
+    meta_dir.mkdir(parents=True, exist_ok=True)
+
+    if not project.components:
+        raise SnapcraftError("Project does not contain any components.")
+
+    component = project.components.get(component_name)
+
+    if not component:
+        raise SnapcraftError("Component does not exist.")
+
+    component_metadata = ComponentMetadata(
+        component=f"{project.name}+{component_name}",
+        type=component.type,
+        version=component.version,
+        summary=component.summary,
+        description=component.description,
+    )
+
+    yaml.add_representer(str, _repr_str, Dumper=yaml.SafeDumper)
+    yaml_data = component_metadata.yaml(
+        by_alias=True,
+        exclude_none=True,
+        allow_unicode=True,
+        sort_keys=False,
+        width=1000,
+    )
+
+    component_yaml = meta_dir / "component.yaml"
+    component_yaml.write_text(yaml_data)
+
+
+def _repr_str(dumper, data):
+    """Multi-line string representer for the YAML dumper."""
+    if "\n" in data:
+        return dumper.represent_scalar("tag:yaml.org,2002:str", data, style="|")
+    return dumper.represent_scalar("tag:yaml.org,2002:str", data)

snapcraft/parts/lifecycle.py

@@ -1,6 +1,6 @@
 # -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
 #
-# Copyright 2022-2023 Canonical Ltd.
+# Copyright 2022-2024 Canonical Ltd.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
@@ -33,7 +33,7 @@
 from snapcraft.elf import Patcher, SonameCache, elf_utils
 from snapcraft.elf import errors as elf_errors
 from snapcraft.linters import LinterStatus
-from snapcraft.meta import manifest, snap_yaml
+from snapcraft.meta import component_yaml, manifest, snap_yaml
 from snapcraft.projects import (
     Architecture,
     ArchitectureProject,
@@ -318,6 +318,16 @@ def _generate_metadata(
     snap_yaml.write(project, lifecycle.prime_dir, arch=project.get_build_for())
     emit.progress("Generated snap metadata", permanent=True)
 
+    if components := project.get_component_names():
+        emit.progress("Generating component metadata...")
+        for component in components:
+            component_yaml.write(
+                project=project,
+                component_name=component,
+                component_prime_dir=lifecycle.get_prime_dir_for_component(component),
+            )
+        emit.progress("Generated component metadata", permanent=True)
+
     if parsed_args.enable_manifest:
         _generate_manifest(
             project,

snapcraft/parts/parts.py

@@ -1,6 +1,6 @@
 # -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
 #
-# Copyright 2022-2023 Canonical Ltd.
+# Copyright 2022-2024 Canonical Ltd.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
@@ -118,6 +118,25 @@ def __init__(  # noqa PLR0913
         except craft_parts.PartsError as err:
             raise errors.PartsLifecycleError(str(err)) from err
 
+    def get_prime_dir_for_component(self, component: str) -> pathlib.Path:
+        """Get the prime directory path for a component.
+
+        :param component: Name of the component to get the prime directory for.
+
+        :returns: The component's prime directory.
+
+        :raises SnapcraftError: If the component does not exist.
+        """
+        try:
+            return self._lcm.project_info.get_prime_dir(
+                partition=f"component/{component}"
+            )
+        except ValueError as err:
+            raise errors.SnapcraftError(
+                f"Could not get prime directory for component {component!r} "
+                "because it does not exist."
+            ) from err
+
     @property
     def prime_dir(self) -> pathlib.Path:
         """Return the parts prime directory path."""

snapcraft/projects.py

@@ -822,6 +822,13 @@ def get_build_for_arch_triplet(self) -> Optional[str]:
 
         return None
 
+    def get_component_names(self) -> List[str]:
+        """Get a list of component names.
+
+        :returns: A list of component names.
+        """
+        return list(self.components.keys()) if self.components else []
+
     def get_partitions(self) -> Optional[List[str]]:
         """Get a list of partitions based on the project's components.
 
@@ -937,6 +944,13 @@ def unmarshal(cls, data: Dict[str, Any]) -> "ComponentProject":
 
         return components
 
+    def get_component_names(self) -> List[str]:
+        """Get a list of component names.
+
+        :returns: A list of component names.
+        """
+        return list(self.components.keys()) if self.components else []
+
     def get_partitions(self) -> Optional[List[str]]:
         """Get a list of partitions based on the project's components.
 

tests/spread/core22/components/simple/snap/expected-man-pages-component.yaml

@@ -0,0 +1,5 @@
+component: snap-with-components+man-pages
+type: test
+version: '1.0'
+summary: Hello World
+description: Hello World

tests/spread/core22/components/simple/task.yaml

@@ -21,3 +21,8 @@ execute: |
     exit 1
   fi
 
+  # assert contents of component metadata
+  if ! diff prime/component/man-pages/meta/component.yaml expected-man-pages-component.yaml; then
+    echo "Metadata for the man-pages component is incorrect."
+    exit 1
+  fi

tests/unit/meta/test_component_yaml.py

@@ -0,0 +1,118 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright 2024 Canonical Ltd.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import textwrap
+from pathlib import Path
+
+import pytest
+
+from snapcraft.errors import SnapcraftError
+from snapcraft.meta import component_yaml
+from snapcraft.meta.component_yaml import ComponentMetadata
+from snapcraft.projects import Project
+
+
+@pytest.fixture
+def stub_project_data():
+    return {
+        "name": "mytest",
+        "version": "1.29.3",
+        "base": "core22",
+        "summary": "Single-line elevator pitch for your amazing snap",
+        "description": "test-description",
+        "confinement": "strict",
+        "parts": {
+            "part1": {
+                "plugin": "nil",
+            },
+        },
+        "apps": {
+            "app1": {
+                "command": "bin/mytest",
+            },
+        },
+        "components": {
+            "component-a": {
+                "type": "test",
+                "summary": "test summary",
+                "description": "test description",
+                "version": "1.0",
+            },
+        },
+    }
+
+
+def test_unmarshal_component():
+    """Unmarshal a dictionary containing a component."""
+    component_data = {
+        "component": "mytest+component-a",
+        "type": "test",
+        "version": "1.0",
+        "summary": "test summary",
+        "description": "test description",
+    }
+
+    component = ComponentMetadata.unmarshal(component_data)
+
+    assert component.component == "mytest+component-a"
+    assert component.type == "test"
+    assert component.version == "1.0"
+    assert component.summary == "test summary"
+    assert component.description == "test description"
+
+
+def test_write_component_yaml(stub_project_data, new_dir):
+    """Write a component.yaml file from a project."""
+    project = Project.unmarshal(stub_project_data)
+    yaml_file = Path("meta/component.yaml")
+
+    component_yaml.write(
+        project, component_name="component-a", component_prime_dir=new_dir
+    )
+
+    assert yaml_file.is_file()
+    assert yaml_file.read_text() == textwrap.dedent(
+        """\
+        component: mytest+component-a
+        type: test
+        version: '1.0'
+        summary: test summary
+        description: test description
+        """
+    )
+
+
+def test_write_component_no_components(stub_project_data, new_dir):
+    """Raise an error if no components are defined."""
+    stub_project_data.pop("components")
+    project = Project.unmarshal(stub_project_data)
+
+    with pytest.raises(SnapcraftError) as raised:
+        component_yaml.write(
+            project, component_name="component-a", component_prime_dir=new_dir
+        )
+
+    assert str(raised.value) == "Project does not contain any components."
+
+
+def test_write_component_non_existent(stub_project_data, new_dir):
+    """Raise an error if the component does not exist."""
+    project = Project.unmarshal(stub_project_data)
+
+    with pytest.raises(SnapcraftError) as raised:
+        component_yaml.write(project, component_name="bad", component_prime_dir=new_dir)
+
+    assert str(raised.value) == "Component does not exist."

tests/unit/parts/test_lifecycle.py

@@ -1,6 +1,6 @@
 # -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
 #
-# Copyright 2022-2023 Canonical Ltd.
+# Copyright 2022-2024 Canonical Ltd.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
@@ -2021,3 +2021,48 @@ def test_lifecycle_write_metadata(
             primed_stage_packages=[],
         )
     ]
+
+
+@pytest.mark.usefixtures("enable_partitions_feature", "project_vars")
+def test_lifecycle_write_component_metadata(
+    snapcraft_yaml, new_dir, mocker, stub_component_data
+):
+    """Component metadata should be written during the lifecycle."""
+    yaml_data = snapcraft_yaml(base="core22", components=stub_component_data)
+    project = Project.unmarshal(snapcraft_yaml(**yaml_data))
+    mocker.patch("snapcraft.parts.PartsLifecycle.run")
+    mocker.patch("snapcraft.pack.pack_snap")
+    mock_write = mocker.patch("snapcraft.meta.component_yaml.write")
+
+    parsed_args = argparse.Namespace(
+        debug=False,
+        destructive_mode=True,
+        use_lxd=False,
+        enable_manifest=True,
+        ua_token=None,
+        parts=[],
+        manifest_image_information=None,
+    )
+
+    parts_lifecycle._run_command(
+        "prime",
+        project=project,
+        parse_info={},
+        assets_dir=Path(),
+        start_time=datetime.now(),
+        parallel_build_count=8,
+        parsed_args=parsed_args,
+    )
+
+    assert mock_write.mock_calls == [
+        call(
+            project=project,
+            component_name="foo",
+            component_prime_dir=new_dir / "prime/component/foo",
+        ),
+        call(
+            project=project,
+            component_name="bar-baz",
+            component_prime_dir=new_dir / "prime/component/bar-baz",
+        ),
+    ]