Improve error message for packages in src folder

[martinvotruba-r7]

Problem description

Currently when a poetry install command is run on a project, which has source stored under src/project_name, but a folder named project_name exists in the root, the command will fail with project_name is not a package. It can be rather hard to determine the root cause, as one might easily overlook the empty folder.

Steps to reproduce

1. create a new poetry project poetry new poetry-demo
2. Move poetry_demo/__init__.py to src/poetry_demo/__init__.py
3. run poetry install

The command will fail with the following

poetry install
Installing dependencies from lock file

Installing the current project: poetry-demo (0.1.0)
poetry_demo is not a package.

This is caused by the presence of poetry_demo folder in the root.

tree -I ".git" --noreport --charset utf-8 .
.
├── README.md
├── poetry.lock
├── poetry_demo
├── pyproject.toml
├── src
│   └── poetry_demo
│       └── __init__.py
└── tests
    └── __init__.py

When I remove the poetry_demo folder, the poetry install command succeeds.

Resolution

To provide more information about the actual root cause of the issue, I have added another validation method to the Factory class. This will output a warning when there is both

• an empty project_name folder in the root
• non-empty src/project_name folder
  The provided warning message is the following

Found empty directory 'project_name' in project root while the actual package is in 'src/project_name'. This may cause issues with package installation. Consider removing the empty directory.

If there is a better place / method how to alert user to the empty project_name folder, I am happy to hear it and adjust my implementation.

• Added tests for changed code.
• Updated documentation for changed code.

[radoering]

If there is a better place / method how to alert user to the empty project_name folder, I am happy to hear it and adjust my implementation.

First thought: This should be part of validate() but not a separate method. However, I see that this is not possible without changing the interface of validate() because validate() only knows about the data in the pyproject.toml and nothing about the project structure. So maybe not such a good idea after all.

Second thought: Somewhere we do check if referenced readme files do exist. That is something similar. Maybe, we should put this check at the same place. We do the readme check in the check command: https://github.com/python-poetry/poetry/blob/a7079acc7631eda4f7ba0f9a34d8d1468d50cba3/src/poetry/console/commands/check.py#L84-L93

Doing it in the check command means you will only get the warning when running poetry check. The advantage is that the code is not executed every time. The disadvantage is that you have to run poetry check to get the warning.

Considering the similarity to the readme check, I think I prefer to move it into the check command.