### Bug Description ## Situation When Rockcraft validates the project file, the errors it provide are inconsistent depending on the key. For example, if `name` is omitted, it prints: ``` Bad rockcraft.yaml content: - field 'name' required in top-level configuration ``` But if `base` is absent, it prints: ``` rockcraft internal error: AttributeError("'NoneType' object has no attribute 'count'") ``` It's impossible to identify the issue from that message. Related to #182. ## Request For the mandatory top-level/metadata/package information keys, we should be providing better validation messages. Those are the most critical for publication and least likely to have actual validation errors. ### To Reproduce Pack the provided project file. ### Environment Ubuntu 24.04. ### rockcraft.yaml ```yaml name: test # see https://documentation.ubuntu.com/rockcraft/en/1.14.0/explanation/bases/ # for more information about bases and using 'bare' bases for chiselled rocks version: '0.1' # just for humans. Semantic versioning is recommended # base: ubuntu@24.04 summary: Single-line elevator pitch for your amazing rock # 79 char long summary description: | This is empty's description. You have a paragraph or two to tell the most important story about it. Keep it under 100 words though, we live in tweetspace and your description wants to look good in the container registries out there. platforms: # the platforms this rock should be built on and run on amd64: parts: my-part: plugin: nil ``` ### Relevant log output ```shell 2025-10-10 11:05:55.253 rockcraft internal error: AttributeError("'NoneType' object has no attribute 'count'") 2025-10-10 11:05:55.257 Traceback (most recent call last): 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/application.py", line 650, in run 2025-10-10 11:05:55.257 return_code = self._run_inner() 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/application.py", line 627, in _run_inner 2025-10-10 11:05:55.257 return_code = dispatcher.run() or os.EX_OK 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_cli/dispatcher.py", line 564, in run 2025-10-10 11:05:55.257 return self._loaded_command.run(self._parsed_command_args) 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/commands/base.py", line 200, in run 2025-10-10 11:05:55.257 result = self._run(parsed_args, **kwargs) or result 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/commands/lifecycle.py", line 591, in _run 2025-10-10 11:05:55.257 return super()._run(parsed_args=parsed_args, step_name=step_name) 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/commands/lifecycle.py", line 204, in _run 2025-10-10 11:05:55.257 self._run_manager_for_build_plan(fetch_service_policy) 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/commands/lifecycle.py", line 95, in _run_manager_for_build_plan 2025-10-10 11:05:55.257 for build in self._services.get("build_plan").plan(): 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/services/buildplan.py", line 64, in plan 2025-10-10 11:05:55.257 self.__plan = self.create_build_plan( 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/services/buildplan.py", line 161, in create_build_plan 2025-10-10 11:05:55.257 self._gen_exhaustive_build_plan(project_data=raw_project), 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_application/services/buildplan.py", line 81, in _gen_exhaustive_build_plan 2025-10-10 11:05:55.257 return craft_platforms.get_build_plan( 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_platforms/_build.py", line 62, in get_build_plan 2025-10-10 11:05:55.257 return planner(**args) 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_platforms/rock/_build.py", line 59, in get_rock_build_plan 2025-10-10 11:05:55.257 return _platforms.get_platforms_build_plan(base, platforms, build_base) 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_platforms/_platforms.py", line 53, in get_platforms_build_plan 2025-10-10 11:05:55.257 distro_base = _distro.DistroBase.from_str(build_base or base) 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2025-10-10 11:05:55.257 File "/snap/rockcraft/3591/lib/python3.12/site-packages/craft_platforms/_distro.py", line 184, in from_str 2025-10-10 11:05:55.257 if base_str.count("@") != 1: 2025-10-10 11:05:55.257 ^^^^^^^^^^^^^^ ```