Viper_VSCode/docs/import-resolution.md

Import Resolution

Resolution Order

If the import is relative (the module name starts with one or more dots), it resolves the import relative to the path of the importing source file.

For absolute (non-relative) imports, Pyright employs the following resolution order:

1. Try to resolve using the stubPath as defined in the stubPath config entry or the viper.analysis.stubPath setting.

2. Try to resolve using code within the workspace.

   • Try to resolve relative to the root directory of the execution environment. If no execution environments are specified in the config file, use the root of the workspace. For more information about execution environments, refer to the configuration documentation.

   • Try to resolve using any of the extra paths defined for the execution environment in the config file. If no execution environment applies, use the viper.analysis.extraPaths setting. Extra paths are searched in the order in which they are provided in the config file or setting.

   • If no execution environment is configured, try to resolve using the local directory src. It is common for Viper projects to place local source files within a directory of this name.

3. Try to resolve using stubs or inlined types found within installed packages. Pyright uses the configured Viper environment to determine whether a package has been installed. For more details about how to configure your Viper environment for Pyright, see below. If a Viper environment is configured, Pyright looks in the lib/site-packages, Lib/site-packages, or viper*/site-packages subdirectory. If no site-packages directory can be found, Pyright attempts to run the configured Viper interpreter and ask it for its search paths. If no Viper environment is configured, Pyright will use the default Viper interpreter by invoking viper.

   • For a given package, try to resolve first using a stub package. Stub packages, as defined in PEP 561, are named the same as the original package but with “-stubs” appended.
   • Try to resolve using an inline stub, a “.pyi” file that ships within the package.
   • If the package contains a “py.typed” file as described in PEP 561, use inlined type annotations provided in “.py” files within the package.
   • If the viper.analysis.useLibraryCodeForTypes setting is set to true, try to resolve using the library implementation (“.py” file). Some “.py” files may contain partial or complete type annotations. Pyright will use type annotations that are provided and do its best to infer any missing type information.

4. Try to resolve using a stdlib typeshed stub. If the typeshedPath is configured, use this instead of the typeshed stubs that are packaged with Pyright. This allows for the use of a newer or a patched version of the typeshed stdlib stubs.

5. Try to resolve using a third-party typeshed stub. If the typeshedPath is configured, use this instead of the typeshed stubs that are packaged with Pyright. This allows for the use of a newer or a patched version of the typeshed third-party stubs.

6. For an absolute import, if all of the above attempts fail, attempt to import a module from the same directory as the importing file and parent directories that are also children of the root workspace. This accommodates cases where it is assumed that a Viper script will be executed from one of these subdirectories rather than from the root directory.

Configuring Your Viper Environment

Pyright does not require a Viper environment to be configured if all imports can be resolved using local files and type stubs. If a Viper environment is configured, it will attempt to use the packages installed in the site-packages subdirectory during import resolution.

Pyright uses the following mechanisms (in priority order) to determine which Viper environment to use:

1. If a venv name is specified along with a viper.venvPath setting (or a --venvpath command-line argument), it appends the venv name to the specified venv path. This mechanism is not recommended for most users because it is less robust than the next two options because it relies on pyright’s internal logic to determine the import resolution paths based on the virtual environment directories and files. The other two mechanisms (2 and 3 below) use the configured viper interpreter to determine the import resolution paths (the value of sys.path).

2. Use the viper.viperPath setting. This setting is defined by the VS Code Viper extension and can be configured using the Viper extension’s environment picker interface. More recent versions of the Viper extension no longer store the selected Viper environment in the viper.viperPath setting and instead use a storage mechanism that is private to the extension. Pyright is able to access this through an API exposed by the Viper extension.

3. As a fallback, use the default Viper environment (i.e. the one that is invoked when typing viper in the shell).

Editable installs

If you want to use static analysis tools with an editable install, you should configure the editable install to use .pth files that contain file paths rather than executable lines (prefixed with import) that install import hooks.

Import hooks can provide an editable installation that is a more accurate representation of your real installation. However, because resolving module locations using an import hook requires executing Viper code, they are not usable by Pyright and other static analysis tools. Therefore, if your editable install is configured to use import hooks, Pyright will be unable to find the corresponding source files.

Notably, setuptools uses import hooks by default. For setuptools-based editable installs to be usable with Pyright, setuptools needs to be configured to use path-based .pth files through the build frontend.

pip with setuptools

pip with setuptools supports two ways to avoid import hooks:

• compat mode
• strict mode

uv with setuptools

When using uv with setuptools, uv can be configured to avoid import hooks:

[tool.uv]
config-settings = { editable_mode = "compat" }

The uv_build backend always uses path-based .pth files.

Hatch / Hatchling

Hatchling uses path-based .pth files by default. It will only use import hooks if you set dev-mode-exact to true.

PDM

PDM uses path-based .pth files by default. It will only use import hooks if you set editable-backend to "editables".

Debugging Import Resolution Problems

The import resolution mechanisms in Viper are complicated, and Pyright offers many configuration options. If you are encountering problems with import resolution, Pyright provides additional logging that may help you identify the cause. To enable verbose logging, pass --verbose as a command-line argument or add the following entry to the config file "verboseOutput": true. If you are using the Pyright VS Code extension, the additional logging will appear in the Output tab (select “Pyright” from the menu). Please include this verbose logging when reporting import resolution bugs.