plugin handler: load legacy plugins prefixed with 'x-'

Required for compatibility.

Signed-off-by: Chris Patterson <chris.patterson@canonical.com>

Author: Chris Patterson

snapcraft/internal/pluginhandler/_plugin_loader.py

@@ -18,6 +18,7 @@
 import importlib
 import logging
 import sys
+from pathlib import Path
 
 import jsonschema
 
@@ -74,21 +75,48 @@ def load_plugin(
     return plugin
 
 
-def _load_local(module_name: str, local_plugin_dir: str):
-    sys.path = [local_plugin_dir] + sys.path
-    logger.debug(f"Loading plugin module {module_name!r} with sys.path {sys.path!r}")
-    try:
-        module = importlib.import_module(module_name)
-    finally:
-        sys.path.pop(0)
+def _load_compat_x_prefix(plugin_name: str, module_name: str, local_plugin_dir: str):
+    compat_path = Path(local_plugin_dir, f"x-{plugin_name}.py")
+    if not compat_path.exists():
+        return None
+
+    preferred_name = f"{module_name}.py"
+    logger.warning(
+        f"Legacy plugin name detected, please rename the plugin's file name {compat_path.name!r} to {preferred_name!r}."
+    )
+
+    spec = importlib.util.spec_from_file_location(plugin_name, compat_path)
+    if spec.loader is None:
+        return None
+
+    # Prevent mypy type complaints by asserting type.
+    assert isinstance(spec.loader, importlib.abc.Loader)
+
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    return module
+
+
+def _load_local(plugin_name: str, local_plugin_dir: str):
+    module_name = plugin_name.replace("-", "_")
+
+    module = _load_compat_x_prefix(plugin_name, module_name, local_plugin_dir)
+    if module is None:
+        sys.path = [local_plugin_dir] + sys.path
+        logger.debug(
+            f"Loading plugin module {module_name!r} with sys.path {sys.path!r}"
+        )
+        try:
+            module = importlib.import_module(module_name)
+        finally:
+            sys.path.pop(0)
 
     return module
 
 
 def _get_local_plugin_class(*, plugin_name: str, local_plugins_dir: str):
     with contextlib.suppress(ImportError):
-        module_name = plugin_name.replace("-", "_")
-        module = _load_local(f"{module_name}", local_plugins_dir)
+        module = _load_local(plugin_name, local_plugins_dir)
         logger.info(f"Loaded local plugin for {plugin_name}")
 
         for attr in vars(module).values():

tests/spread/plugins/v1/x-local/local-plugin-x-compat/state-pull

@@ -0,0 +1,32 @@
+!PullState
+assets:
+  build-packages: !!set {}
+  build-snaps: !!set {}
+  source-details: null
+  stage-packages: []
+extracted_metadata:
+  files: []
+  metadata: !ExtractedMetadata
+    _data: {}
+    common_id_list: []
+project_options:
+  deb_arch: @EXPECTED_ARCHITECTURE@
+properties:
+  foo: null
+  override-pull: snapcraftctl pull
+  parse-info: []
+  plugin: local-plugin
+  source: .
+  source-branch: ''
+  source-commit: ''
+  source-depth: 0
+  source-subdir: ''
+  source-tag: ''
+  source-type: ''
+  stage-packages: []
+schema_properties:
+- foo
+- stage-packages
+scriptlet_metadata: !ExtractedMetadata
+  _data: {}
+  common_id_list: []

tests/spread/plugins/v1/x-local/local-plugin-x-compat/task.yaml

@@ -0,0 +1,43 @@
+summary: Use local plugins to build a snap
+
+environment:
+  SNAP_DIR/xcompat1: ../snaps/x-compat-name
+
+prepare: |
+  #shellcheck source=tests/spread/tools/snapcraft-yaml.sh
+  . "$TOOLS_DIR/snapcraft-yaml.sh"
+  set_base "$SNAP_DIR/snap/snapcraft.yaml"
+
+  deb_arch=$(dpkg --print-architecture)
+  sed -i state-pull -e"s/\(.*deb_arch:\) @EXPECTED_ARCHITECTURE@$/\1 $deb_arch/"
+
+restore: |
+  expected_pull_state="$(pwd)/state-pull"
+
+  cd "$SNAP_DIR"
+  snapcraft clean
+  rm -f ./*.snap
+
+  #shellcheck source=tests/spread/tools/snapcraft-yaml.sh
+  . "$TOOLS_DIR/snapcraft-yaml.sh"
+  restore_yaml "snap/snapcraft.yaml"
+
+  git checkout "${expected_pull_state}"
+
+execute: |
+  expected_pull_state="$(pwd)/state-pull"
+
+  cd "$SNAP_DIR"
+
+  snapcraft build
+
+  if [ ! -f parts/x-local-plugin/install/build-stamp ]; then
+      echo "Local plugin failed to create 'build-stamp"
+      exit 1
+  fi
+
+  if ! diff -U10 parts/x-local-plugin/state/pull "$expected_pull_state"; then
+    echo "Pull state does not match"
+    exit 1
+  fi
+

tests/spread/plugins/v1/x-local/snaps/x-compat-name/snap/plugins/x-local-plugin.py

@@ -0,0 +1,38 @@
+# -*- Mode:Python; indent-tabs-mode:nil; tab-width:4 -*-
+#
+# Copyright (C) 2015 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/>.
+
+from snapcraft import BasePlugin
+
+
+class LocalPlugin(BasePlugin):
+    @classmethod
+    def schema(cls):
+        schema = super().schema()
+
+        schema["properties"]["foo"] = {"type": "string"}
+
+        return schema
+
+    @classmethod
+    def get_pull_properties(cls):
+        return ["foo", "stage-packages"]
+
+    @classmethod
+    def get_build_properties(cls):
+        return ["foo", "stage-packages"]
+
+    def build(self):
+        return self.run(["touch", "build-stamp"], self.installdir)

tests/spread/plugins/v1/x-local/snaps/x-compat-name/snap/snapcraft.yaml

@@ -0,0 +1,12 @@
+name: test-local-plugins
+base: core18
+version: "0.1"
+summary: local plugin in snap/plugins
+description: Tests if local plugins load and can build
+confinement: strict
+grade: devel
+
+parts:
+    x-local-plugin:
+      plugin: local-plugin
+      source: .