chore: clean up code

docs/explanation/extensions/expressjs-framework.rst

@@ -15,24 +15,6 @@ Ubuntu base and Node combinations
 In this section of the document, we will discuss the possible combinations of
 Ubuntu bases and possible usages of NPM plugin.
 
-24.04 base and Node from NPM plugin
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-The following example uses the Ubuntu 24.04 base and Node from the NPM plugin.
-
-.. code-block:: yaml
-
-    base: [email protected]
-    extensions:
-    - expressjs-framework
-    parts:
-        expressjs-framework/install-app:
-            npm-include-node: true
-            npm-node-version: 20.12
-
-In this case, the application is installed and run via Node and NPM installed by
-the NPM plugin.
-
 24.04 base and Node from Ubuntu packages
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -43,9 +25,6 @@ The following example uses the Ubuntu 24.04 base and Node from Ubuntu packages.
     base: [email protected]
     extensions:
     - expressjs-framework
-    parts:
-        expressjs-framework/install-app:
-            npm-include-node: false
 
 In this case, the application is installed and run via Node and NPM installed by
 the Ubuntu packages. The NPM and Node versions are determined by the versions of
@@ -55,24 +34,23 @@ the corressponding Ubuntu base from the chilsel-slices repository. This
 blob/ubuntu-24.04/slices/nodejs.yaml) is an example of the NodeJS version
 shipped with the Ubuntu 24.04 base.
 
-Bare base and Node from NPM plugin
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+24.04 base and Node from NPM plugin
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-The following example uses the bare base and Node from the NPM plugin.
+The following example uses the Ubuntu 24.04 base and Node from the NPM plugin.
 
 .. code-block:: yaml
 
-    base: bare
-    build-base: [email protected]
+    base: [email protected]
+    extensions:
+    - expressjs-framework
     parts:
         expressjs-framework/install-app:
             npm-include-node: true
             npm-node-version: 20.12
 
 In this case, the application is installed and run via Node and NPM installed by
-the NPM plugin. For different possible inputs for npm-node-version, refer to the
-[NPM plugin documentation](https://documentation.ubuntu.com/rockcraft/en/\
-latest/common/craft-parts/reference/plugins/npm_plugin).
+the NPM plugin.
 
 Bare base and Node from Ubuntu packages
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -83,9 +61,6 @@ The following example uses the bare base and Node from Ubuntu packages.
 
     base: bare
     build-base: [email protected]
-    parts:
-        expressjs-framework/install-app:
-            npm-include-node: false
 
 In this case, the application is installed and run via Node and NPM installed by
 the Ubuntu packages. The NPM and Node versions are determined by the versions of
@@ -98,3 +73,22 @@ shipped with the Ubuntu 24.04 base.
 See the NPM version shipped with the corressponding Ubuntu base from the Ubuntu
 packages archive from the [Ubuntu packages search](https://packages.ubuntu.com/\
 search?suite=default&section=all&arch=any&keywords=npm&searchon=names)
+
+Bare base and Node from NPM plugin
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The following example uses the bare base and Node from the NPM plugin.
+
+.. code-block:: yaml
+
+    base: bare
+    build-base: [email protected]
+    parts:
+        expressjs-framework/install-app:
+            npm-include-node: true
+            npm-node-version: 20.12
+
+In this case, the application is installed and run via Node and NPM installed by
+the NPM plugin. For different possible inputs for npm-node-version, refer to the
+[NPM plugin documentation](https://documentation.ubuntu.com/rockcraft/en/\
+latest/common/craft-parts/reference/plugins/npm_plugin).

rockcraft/extensions/expressjs.py

@@ -42,22 +42,6 @@ def is_experimental(base: str | None) -> bool:
         """Check if the extension is in an experimental state."""
         return True
 
-    @override
-    def get_part_snippet(self) -> dict[str, Any]:
-        """Return the part snippet to apply to existing parts.
-
-        This is unused but is required by the ABC.
-        """
-        return {}
-
-    @override
-    def get_parts_snippet(self) -> dict[str, Any]:
-        """Return the parts to add to parts.
-
-        This is unused but is required by the ABC.
-        """
-        return {}
-
     @override
     def get_root_snippet(self) -> dict[str, Any]:
         """Fill in some default root components.
@@ -96,6 +80,22 @@ def get_root_snippet(self) -> dict[str, Any]:
             snippet["parts"]["expressjs-framework/runtime"] = runtime_part
         return snippet
 
+    @override
+    def get_part_snippet(self) -> dict[str, Any]:
+        """Return the part snippet to apply to existing parts.
+
+        This is unused but is required by the ABC.
+        """
+        return {}
+
+    @override
+    def get_parts_snippet(self) -> dict[str, Any]:
+        """Return the parts to add to parts.
+
+        This is unused but is required by the ABC.
+        """
+        return {}
+
     def _check_project(self) -> None:
         """Ensure this extension can apply to the current rockcraft project.
 
@@ -112,15 +112,22 @@ def _check_project(self) -> None:
                 doc_slug="/reference/extensions/expressjs-framework",
                 logpath_report=False,
             )
-        if "name" not in self._app_package_json:
+        if "name" not in self._app_package_json or not isinstance(
+            self._app_package_json["name"], str
+        ):
             raise ExtensionError(
                 "missing application name",
                 doc_slug="/reference/extensions/expressjs-framework",
                 logpath_report=False,
             )
 
     def _gen_install_app_part(self) -> dict:
-        """Generate the install app part using NPM plugin."""
+        """Generate the install app part using NPM plugin.
+
+        Set the script shell to bash and copy the .npmrc file to the app
+        directory. This is to ensure that the ExpressJS run in bare container
+        can use the shell to launch itself.
+        """
         install_app_part: dict[str, Any] = {
             "plugin": "npm",
             "source": f"{self.IMAGE_BASE_DIR}/",
@@ -132,10 +139,10 @@ def _gen_install_app_part(self) -> dict:
                 f"ln -s /lib/node_modules/{self._app_name} ${{CRAFT_PART_INSTALL}}/app\n"
             ),
         }
-        build_packages = self._install_app_build_packages
+        build_packages = self._gen_app_build_packages()
         if build_packages:
             install_app_part["build-packages"] = build_packages
-        stage_packages = self._install_app_stage_packages
+        stage_packages = self._gen_app_stage_packages()
         if stage_packages:
             install_app_part["stage-packages"] = stage_packages
         if self._user_npm_include_node:
@@ -145,15 +152,13 @@ def _gen_install_app_part(self) -> dict:
             )
         return install_app_part
 
-    @property
-    def _install_app_build_packages(self) -> list[str]:
+    def _gen_app_build_packages(self) -> list[str]:
         """Return the build packages for the install app part."""
         if self._user_npm_include_node:
             return []
         return ["nodejs", "npm"]
 
-    @property
-    def _install_app_stage_packages(self) -> list[str]:
+    def _gen_app_stage_packages(self) -> list[str]:
         """Return the stage packages for the install app part."""
         if self._rock_base == "bare":
             return [
@@ -203,7 +208,21 @@ def _app_package_json(self) -> dict:
                 logpath_report=False,
             )
         package_json_contents = package_json_file.read_text(encoding="utf-8")
-        return json.loads(package_json_contents)
+        try:
+            app_package_json = json.loads(package_json_contents)
+            if not isinstance(app_package_json, dict):
+                raise ExtensionError(
+                    "invalid package.json file",
+                    doc_slug="/reference/extensions/expressjs-framework",
+                    logpath_report=False,
+                )
+            return app_package_json
+        except json.JSONDecodeError as exc:
+            raise ExtensionError(
+                "failed to parse package.json file",
+                doc_slug="/reference/extensions/expressjs-framework",
+                logpath_report=False,
+            ) from exc
 
     @property
     def _app_name(self) -> str:

rockcraft/templates/expressjs-framework/rockcraft.yaml.j2

@@ -2,7 +2,6 @@ name: {{name}}
 # see {{versioned_url}}/explanation/bases/
 # for more information about bases and using 'bare' bases for chiselled rocks
 base: [email protected] # as an alternative, a 'bare' base can be used
-build-base: [email protected] # build-base is required when the base is bare
 version: '0.1' # just for humans. Semantic versioning is recommended
 summary: A summary of your ExpresssJS application # 79 char long summary
 description: |