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Pyrefly Configuration

Pyrefly has a basic configuration that can (or will) allow you to customize your Pyrefly runs without having to specify all of your arguments on the command line.

NOTE: this is early in its development, so the options listed here are subject to change in name, usage, type, quantity, and structure.

Configurations can be specified in a TOML file at the root of your project (or elsewhere, as long as the path-based config options point to the right place) named pyrefly.toml, with all configuration options in the top-level of the document. You can also specify a configuration in a pyproject.toml under a [tool.pyrefly] section. Other config names can be used when explicitly passing in the config file name with the --config/-c flag, but they will not be automatically found by Configuration Finding.

Both absolute and config-relative paths are supported.

info

Want type error squiggles to show up in your editor by default? Try setting python.pyrefly.displayTypeErrors to "force-on" in your editor settings, create a pyrefly.toml file in your project root, or add a [tool.pyrefly] section to your pyproject.toml (can be empty).

Simple Configuration Example​

Here's an example of a simple config. To see more complex examples, including in a pyproject.toml, look at Example Configurations, which show Pyrefly's default config, as well as other ways you can set your configuration.

# set the directory Pyrefly will search for files to type check
project-includes = [
    "a", "b/c/d", "e"
]

# manually set the `sys.platform` Pyrefly will assume when type checking
python-platform = "linux"

# a table mapping error codes to an `is-enabled` boolean
[errors]
# disable `bad-assignment` errors
bad-assignment = false
# disable `bad-return` errors
bad-return = false

Precedence in Options​

Configuration options are selected in the following order

  1. CLI flags
    • Examples: --project-excludes <value>, --python-version <value>
  2. Configuration options
    • Examples: (in a pyrefly.toml) project-excludes = <value>, python-version = <value>
  3. Pyrefly defaults

Type Checking Modes​

Pyrefly has two different modes it can run in when type checking your project, which correspond to different but useful ways we expect most people to interact with Pyrefly:

  • Project mode: attempt to load a config, falling back to Pyrefly's default config when none can be found, and type check using that one config. This involves getting the project-includes and project-excludes from the file, expanding the patterns, and type checking on those files.
    • Project mode is used whenever no files are provided with the CLI invocation.
  • Per-file or Single-file mode: when given FILES... (and optionally --project-excludes) during a CLI invocation, expand the patterns and find the relevant config file for each file listed. project-includes and project-excludes are ignored from the config file, but it is used for all remaining config options.

Configuration Finding​

In both project checking mode and single-file checking mode (see Type Checking Modes for more info), we attempt to find a project root from which to check each file, both for reading config options and for import resolution. The project root is typically the directory containing the configuration file. More precisely:

  1. If a configuration file is provided with -c/--config, we use the directory the file is located in as the directory to check.
  2. If no configuration file is passed, we perform an upward file search from the 'start location' to the filesystem root, looking in each directory for any of the following files: pyrefly.toml, pyproject.toml, setup.py, mypy.ini, and pyrightconfig.json. If we find one, we use the directory it's found in as the containing directory.
  3. If no configuration file is found, we will still attempt to resolve imports by walking up the tree looking for a matching import. For example: when importing from a.b.c import q, if our project structure looks like /x/y/z/a/b/c, we can walk up the components of a.b.c to find a root at /x/y/z.

Note that only pyrefly.toml and pyproject.toml are parsed for config options, but we look for additional files that mark the root of a project to aid import resolution.

For project checking mode, the 'start location' is current working directory. For single-file checking mode, the start location is the directory containing each file to be type checked, and we find the config for each file matched by the pattern provided.

If a pyrefly.toml is found, it is parsed and used for type checking, and will return an error to the user on invalid types, syntax, values, or unknown config options.

If a pyproject.toml is found, Pyrefly will use the [tool.pyrefly] section if it exists, otherwise it will assume a default config. The same errors will be returned as when loading a pyrefly.toml if the config is invalid.

Providing a Config in Single-File Mode​

Providing -c/--config in single-file checking mode disables the upward file search for config files. All options are read from the provided config file except project-includes and project-excludes, which are ignored.

Configuration Options​

The following section lists all recognized options that can be specified in a config file or pyproject.toml Pyrefly config section.

project-includes​

The glob patterns used to describe which files to type check, typically understood as user-space files.

This does not specify Import Resolution priority or the path an import should be resolved from. See search-path instead.

  • Type: list of filesystem glob patterns
  • Default: ["**/*.py*"]
  • Flag equivalent: FILES... argument
  • Equivalent configs: include in Pyright, files/modules/packages in mypy
  • Notes:
    • When overridden by passing in FILES..., we do not consult the relevant config file for what to use for project-excludes. If project-excludes should not use the default value, override it with the flag as well. This is because if multiple configs are loaded that conflict with project-includes, determining how to resolve checkable files gets complicated, and might become confusing to anyone attempting a type check if they're unaware of all the configs that will be used in the type check. Also, we get into a chicken-and-egg problem, where we don't know which files to exclude until we load all the configs we'll need, which requires loading all files, and imposes a large performance burden.
    • When a project-includes pattern does not match any files, we will return an error.
    • If you get an error about no matches for a directory when passing a glob as a CLI argument, try wrapping the glob in quotes to prevent eager shell glob expansion.

project-excludes​

The glob patterns used to describe which files to avoid type checking as way to filter files that match project-includes, but we don't want to type check.

The default value is appended to your project-excludes unless disable-project-excludes-heuristics is set. See disable-project-excludes-heuristics to fully replace or remove project-excludes.

  • Type: list of filesystem glob patterns
  • Default: ["**/node_modules", "**/__pycache__", "**/venv/**", "**/.[!/.]*/**"] + anything in your site-package-path (even from the interpreter) unless it would exclude items in your search-path.
  • Flag equivalent: --project-excludes
  • Equivalent configs: exclude in Pyright and mypy
  • Notes:
    • While not explicitly part of project-excludes, there are several patterns that are filtered out of type checked files at our glob-implementation layer.
      • Dotfiles (any files that begin with a dot (.<stuff>)
      • Any files that don't end in .py or .pyi
      • Your site-package-path (including paths queried from the interpreter)
    • It is an error if no files are returned from any project-includes because they are filtered out by project-excludes entries. We differentiate between an error from a project-includes that doesn't match any files, and an error from all project-includes getting filtered by project-excludes.
    • When overridden by passing in FILES..., we do not consult the relevant config file for what to use for project-excludes. If project-excludes should not use the default value, override it with the flag as well. See reasoning in project-includes notes.
    • Your site-package-path is added to your project-excludes automatically. If you are trying to perform type checking on a dependency in your site-package-path (i.e. cd <site-package-path>/some_dependency && pyrefly check), we recommend you pull and set up your dependency from GitHub, but you can achieve this on files in your site-package-path by setting site-package-path = [] in your config.

disable-project-excludes-heuristics​

By default, Pyrefly includes several items in your project-excludes (see project-excludes for the default values). These items are path patterns we've determined rarely have files that should be type checked, but can require a very long time to crawl while enumerating files, or contain third-party code that you likely don't care about errors in. When specifying project-excludes, we always append these defaults to whatever is specified by CLI or in your configuration.

Sometimes, these preselected settings can interfere with your project's setup. disable-project-excludes-heuristics lets you start from scratch, setting that default to [], so you can fully specify your project-excludes in case we get it wrong.

  • Type: bool
  • Default: false
  • Flag equivalent: --disable-project-excludes-heuristics

search-path​

A file path describing the roots from which imports should be found and imported from (including modules in project-includes). This takes the highest precedence in import order, before typeshed and site-package-path. When a project-includes type checked file is imported by another type checked file, we check all search roots to determine how to import it.

  • Type: list of directories specifying the root
  • Default: import root
  • Flag equivalent: --search-path
  • Equivalent configs: extraPaths in Pyright, mypy_path in mypy
  • Notes:
    • We automatically apply some heuristics to improve your experience, especially when no configuration is provided. See disable-search-path-heuristics to disable this behavior, and Search Path Heuristics for the additional paths we add to your search-path.
    • Libraries should not be listed here, since they may override typeshed values for your whole project, and have different import semantics with respect to typing. See Import Resolution for more information about how modules are imported.

disable-search-path-heuristics​

Disable any search path heuristics/additional search path behavior that Pyrefly will attempt to do for you. This can be useful if Pyrefly is picking up the wrong import paths for your project, for example, if you have multiple projects in the same directory or use a monorepo setup with the import root outside of the directory your configuration is defined in.

See Search Path Heuristics for more information on the search paths that are automatically added, and are affected by this flag. For more information on import resultion in general see the import resolution docs.

  • Type: bool
  • Default: false
  • Flag equivalent: --disable-search-path-heuristics
  • Equivalent configs: none
  • Notes
    • To see what search path we find for your a given file in your project, or your project overall, you can run pyrefly dump-config [<file>...].

Search Path Heuristics​

Pyrefly adds extra search paths to your configuration behind-the-scenes to handle the most common ways of setting up and configuring your project, on top of any search-path entries you may pass in through the CLI or set in your config.

The two heuristics that are currently supported are:

  1. Adding your import root to the end of your search path. Your import root is a src/ directory in the same directory as a config file, the parent directory containing your config file if there's an __init__.py or __init__.pyi present or the config file's directory itself if none of the previously mentioned directories or files can be found. See Configuration Finding for more information on what we'll find as a config file.
  2. If no config can be found, each directory from the given file to / will be added as a fallback search path.

See more on how Pyrefly does import resolution.

site-package-path​

A file path describing a root from which imports should be found and imported from. This takes the lowest priority in import resolution, after search-path and typeshed.

See more on how Pyrefly does import resolution.

  • Type: list of directories
  • Default: ./typings + the result from Environment Autoconfiguration, or [] if the Python interpreter cannot be queried
  • Flag equivalent: --site-package-path
  • Equivalent configs: none
  • Notes:
    • The queried interpreter's site package paths will always be included in addition to any user-specified value, unless environment auto-configuration is turned off.
    • Ideally, this should not be set manually, unless you're using a venv, running one-off tests, testing specific behavior, or having trouble with Environment Autoconfiguration. Setting this explicitly, especially when not using a venv, will make it difficult for your configuration to be reused between different systems and platforms.
    • If you're running into problems with editiable installations in your project, please read up on editable installs with static analysis tools.

python-platform​

The value used with conditions based on type checking against sys.platform values.

  • Type: string
  • Default: result from Environment Autoconfiguration, or "linux" if the Python interpreter cannot be queried
  • Flag equivalent: --python-platform
  • Equivalent configs: pythonPlatform in Pyright, platform in mypy

python-version​

The value used with conditions based on type checking against sys.version values. The format should be <major>[.<minor>[.<micro>]], where minor and micro can be omitted to take the default positional value.

  • Type: string of the format <major>[.<minor>[.<micro>]]
  • Default: result from Environment Autoconfiguration, or 3.13.0 if the Python interpreter cannot be queried
  • Flag equivalent: --python-version
  • Equivalent configs: pythonVersion in Pyright, python_version in mypy

conda-environment​

The name of the Conda environment to query when attempting to autoconfigure Python environment values (site-package-path, python-platform, python-version). See the Environment Autoconfiguration section for more information. We query Conda with conda info --envs, then find the environment's interpreter in Environment Autoconfirugration.

We will query Conda for information about this environment, even when it's not sourced, unless a Python environment (venv, Conda) is activated or --python-interpreter-path or --conda-environment are passed in through the CLI.

conda-environment, fallback-python-interpreter-name, conda-environment, and skip-interpreter-query are mutually exclusive with each other.

  • Type: string of existing Conda environment name
  • Default: none
  • Flag equivalent: --conda-environment
  • Equivalent configs: none
  • Notes:
    • This enables the use of a non-local but customizable global environment without having to hard-code a path, which is not preferable on a shared project.

python-interpreter-path​

The Python interpreter to query when attempting to autoconfigure Python environment values (site-package-path, python-platform, python-version). See the Environment Autoconfiguration section for more information.

conda-environment, fallback-python-interpreter-name, conda-environment, and skip-interpreter-query are mutually exclusive with each other.

  • Type: path to executable
  • Default: $(which python3), then $(which python), or none
  • Flag equivalent: --python-interpreter-path
  • Equivalent configs: python_executable in mypy
  • Notes:
    • This executes the value present in the python-interpreter-path field without any checks. It could be a security risk if your python-interpreter-path is an arbitrary executable.
    • If you don't have a Python interpreter installed on your machine, we'll output an error letting you that we couldn't appropriately configure your environment. Configure skip-interpreter-query to skip the check and avoid the error.

NOTE: Ideally, this should not be set manually, unless you're using a venv, running one-off tests, testing specific behavior, or having trouble with Environment Autoconfiguration. Setting this explicitly, especially when not using a venv, will make it difficult for your configuration to be reused between different systems and platforms.

fallback-python-interpreter-name​

The Python interpreter, available on your $PATH, to use. Pyrefly will perform which <your command>, and automatically fill in python-interpreter-path for you with the found path. Pyrefly will automatically search for python3 and python on your path when this option and python-interpreter-path are unset if skip-interpreter-query = false, so this should primarily be used when you have a non-standard Python executable you want to use.

conda-environment, fallback-python-interpreter-name, conda-environment, and skip-interpreter-query are mutually exclusive with each other.

  • Type: string of command to use
  • Default: python3, then python, or none
  • Flag equivalent: --fallback-python-interpreter-name
  • Notes:
    • This executes the value present in the fallback-python-interpreter-name field without any checks. It could be a security risk if your fallback-python-interpreter-name is an arbitrary executable.
    • If you don't have a Python interpreter installed on your machine, we'll output an error letting you that we couldn't appropriately configure your environment. Configure skip-interpreter-query to skip the check and avoid the error.

skip-interpreter-query​

Skip querying any interpreters and do not do any Environment Autoconfiguration. This means that Pyrefly will take hard-coded defaults for python-version and python-platform, and will use an empty site-package-path. It's likely you'll want to override these to match the environment you'll be running in.

conda-environment, fallback-python-interpreter-name, conda-environment, and skip-interpreter-query are mutually exclusive with each other.

  • Type: bool
  • Default: false
  • Flag equivalent: --skip-interpreter-query

typeshed-path​

Override the version of typeshed that's being used for type checking. The provided path should point to the root of typeshed.

Typeshed contains the type information for Python's standard library, which Pyrefly uses for type checking and resolving both the most basic types (like object, str, ...) and types/type signatures from stdlib modules.

  • Type: path to typeshed
  • Default: none (resolves to bundled typeshed)
  • Flag equivalent: --typeshed-path

baseline​

Path to a baseline JSON file for comparing type errors. Errors matching the baseline are suppressed, so only newly-introduced errors are reported. This is useful when introducing type checking to a project for the first time, or when rolling out changes that would otherwise produce many new errors at once.

To generate (or re-generate) the baseline file, run:

pyrefly check --baseline="<path to baseline file>" --update-baseline

See the Error Suppressions docs for more details on how baseline files work.

  • Type: path to a JSON file
  • Default: none (no baseline)
  • Flag equivalent: --baseline
  • Notes:
    • baseline is a project-level setting and cannot be overridden in sub-config sections.
    • Errors suppressed by the baseline file are still shown in the IDE.
    • Errors are matched with the baseline by file, error code, and column number.

errors​

Configure the severity for each kind of error that Pyrefly emits: error, warn, ignore.

info

Want type error squiggles to show up in your editor by default? Try setting python.pyrefly.displayTypeErrors to "force-on" in your editor settings, create a pyrefly.toml file in your project root, or add a [tool.pyrefly] section to your pyproject.toml (can be empty).

  • Type: Table of error code to boolean representing enabled status
  • Default: errors = {}/[errors]
  • Flag equivalent: --error, --warn, --ignore
  • Equivalent configs: type check rule overrides and type evaluation settings in Pyright, enable_error_code and disable_error_code in mypy
  • Notes:
    • Setting <error-code> = true means the error will be shown at default severity (or severity ERROR if the error is off by default). Setting <error-code> = false will disable the error for type checking.
    • If you want to disable type errors in IDE mode, you can also set disable-type-errors-in-ide, which will automatically disable all type errors and Pyrefly diagnostics in the IDE.

disable-type-errors-in-ide​

Disables type errors from showing up when running Pyrefly in an IDE. This is primarily used when Pyrefly is acting in a language-server-only mode, but some kind of manual configuration is necessary for it to work properly, or when you would only want to see type errors on CLI/CI runs.

  • Type: bool
  • Default: false
  • Flag equivalent: none
  • Notes: if you want to disable errors on CLI/CI runs as well, or if you're looking to turn on/off specific errors, you may be looking for the errors config option instead.

skip-lsp-config-indexing​

Disables automatic project indexing when running Pyrefly as a language server. Enabling this may speed up LSP startup and reduce resource usage on large projects, at the cost of some language server features that rely on a full project index.

  • Type: bool
  • Default: false
  • Flag equivalent: none

replace-imports-with-any​

Instruct Pyrefly to unconditionally replace the given ModuleGlobs with typing.Any and ignore import errors for the module. For example, with from x.y import z in a file, adding x.*, *.y, or x.y to this config will silence those import errors and replace the module with typing.Any. If the module can be found, its type information will still be replaced with typing.Any.

This is different from ignore-missing-imports, which only replaces the import with typing.Any if it can't be found.

  • Type: list of regex
  • Default: []
  • Flag equivalent: --replace-imports-with-any
  • Equivalent configs: follow_imports = skip in mypy

ignore-missing-imports​

Instruct Pyrefly to replace the given ModuleGlobs with typing.Any and ignore import errors for the module only when the module can't be found.

For example, with from x.y import z in a file, adding x.*, *.y, or x.y to this config will silence those import errors and replace the module with typing.Any if x.y can't be found. If x.y can be found, then z's type will be used.

This is different from replace-imports-with-any, which will always, unconditionally replace the import with typing.Any.

  • Type: list of regex
  • Default: []
  • Flag equivalent: --ignore-missing-imports
  • Equivalent configs: ignore_missing_imports in mypy
  • Notes:
    • errors = {missing-import = false} (TOML inline table for errors) has similar behavior in Pyrefly, but ignores all import errors instead of import errors from specific modules.
    • When a .pyc file is encountered and no source/stub files are available, Pyrefly automatically treats module as typing.Any. This behavior ensures that compiled Python files without available source code do not cause import errors and are handled permissively.

ignore-errors-in-generated-code​

Whether to ignore type errors in generated code. If enabled, generated files will be treated as if they are included in project-excludes. The generated code status is determined by checking if the file contents contain the substring '@generated'.

  • Type: bool
  • Default: false
  • Flag equivalent: --ignore-errors-in-generated-code
  • Equivalent configs: none

infer-with-first-use​

Whether to infer type variables not determined by a call or constructor based on their first usage. This includes empty containers like [] and {}.

The default behavior is similar to Mypy - the type of the variable is inferred based on the first usage.

x = []
x.append(1)  # x is list[int]
x.append("2")  # error!

Setting this to false will make Pyrefly infer Any for unsolved type variables, which behaves like Pyright.

x = []  # x is list[Any]
x.append(1)  # ok
x.append("2")  # ok
  • Type: bool
  • Default: true
  • Flag equivalent: --infer-with-first-use

untyped-def-behavior​

How should Pyrefly treat function definitions with no parameter or return type annotations?

By default, Pyrefly uses the "check-and-infer-return-type" behavior and will check all function bodies, inferring the return type.

info

To provide inferred return types with check-and-infer-return-type, especially for site-package paths (third-party packages), Pyrefly may need to load and analyze more modules than you might otherwise see from mypy.

This may result in increased type check durations or an output showing more modules analyzed than you expect. If this behavior is not preferred, you should set untyped-def-behavior to skip-and-infer-return-any in your config or pass it in as a flag.

If this option is set to "check-and-infer-return-any", then Pyrefly will still check the function body but will treat the return type as Any.

If this option is set to "skip-and-infer-return-any", Pyrefly will again treat the return type as Any, but will also skip checking the function body. In this case, Pyrefly will also infer Any as the type of any attributes inferred based on this function body. This behavior is what PEP 484 specifies, although we do not recommend it for most users today; since Pyrefly will not analyze the bodies of untyped functions, language server functionality like showing types on hover and finding definitions will not be available there.

info

skip-and-infer-return-any is mypy's default inference behavior, and how we will attempt to migrate your existing mypy configuration when running pyrefly init. See Migrating from Mypy for more information on config migration.

  • Type: one of "check-and-infer-return-type", "check-and-infer-return-any", "skip-and-infer-return-any"
  • Default: "check-and-infer-return-type"
  • Flag equivalent: --untyped-def-behavior
  • Equivalent configs:
    • The "check-and-infer-return-type" behavior emulates Pyright's default behavior.
    • The "skip-and-infer-return-any" behavior emulates mypy's default behavior.
    • The "check-and-infer-return-any" behavior emulates mypy's check_untyped_defs flag.

use-ignore-files​

Whether to allow Pyrefly to use ignore files in your project and automatically add excluded files and directories to your project-excludes. Similar to project-excludes, when explicitly specifying files to check, ignore files are not used.

Pyrefly automatically searches for ignore files such as .gitignore, .ignore, and .git/info/excludes in an upward search from your project root. Only the first of each type of ignore file will be used, so if you have a .gitignore and .git/info/excludes available, in different directories, Pyrefly will use both of them. Pyrefly will not use global ignore files.

When multiple ignore files are found, Pyrefly checks them for excludes matches when determining the files to type check in the order of .gitignore, .ignore, and .git/info/excludes, taking the result of the first ignore file that has a match (either allowlist or denylist). Regular .gitignore-style allowlist/denylist matching rules apply.

  • Type: bool
  • Default: true
  • Flag equivalent: --use-ignore-files

build-system​

Pyrefly supports integrating into build systems to discover targets to type check and their dependencies. It currently natively supports Buck2, as well as arbitrary build systems via custom queries.

Note that support for build systems is currently unstable, and breakage may occur without notice. Support will likely be lower priority than other issues for a while.

Buck2​

To configure Pyrefly to use Buck2 as a build system, add the following to your pyrefly.toml:

[build-system]
type = "buck"
# Optional: The isolation dir for Buck2 to use.
isolation-dir = "pyrefly"
# Optional: Extra flags passed to Buck2.
extras = ["--verbose", "4"]

Behind the scenes, Pyrefly will run the prelude//python/sourcedb/pyrefly.bxl:main BXL script to get the necessary information about the targets to type check.

Here is a description of the supported optional options:

isolation-dir

Name of the isolation dir to use when running the BXL query (see buck2 --help or Buck's documentation for more information about isolation dirs).

Type: string Default: none (Buck's own default is v2)

extras

Extra command line arguments passed to buck2 when running the query.

  • Type: list of strings
  • Default: []

Custom queries​

Arbitrary build systems can be integrated using the custom type:

[build-system]
type = "custom"
command = ["some", "command", "..."]

Here is a description of the supported options:.

command

The command executed to query the build system about available targets.

Pyrefly will call this in the form <command...> @<argfile>, where <argfile> has the format:

--
<arg-flag>
<arg>
...

<arg-flag> is either --file or --target, depending on the type of <arg>, and <arg> is an absolute path to a file or a build system's target.

The command should output a JSON file with the following structure:

{
    "root": "/path/to/this/repository",
    "db": {
        "//colorama:py-stubs": {
            "srcs": {
                "colorama": [
                    "colorama/__init__.pyi"
                ]
            },
            "deps": [],
            "buildfile_path": "colorama/BUCK",
            "python_version": "3.12",
            "python_platform": "linux"
        },
        "//colorama:py": {
            "srcs": {
                "colorama": [
                    "colorama/__init__.py"
                ]
            },
            "deps": ["//colorama:py-stubs"],
            "buildfile_path": "colorama/BUCK",
            "python_version": "3.12",
            "python_platform": "linux"
        },
        "//colorama:colorama": {
            "alias": "//colorama:py"
        }
    }
}

Where:

  • root is the absolute path the root of the repository.
  • db is a map from target names to either:
    • library target definitions (e.g. //colorama:py and //colorama:py-stubs here)
    • target aliases (e.g. //colorama:colorama here)

For reference, the command invoked as part of the Buck2 integration is:

buck2 [--isolation-dir <isolation_dir>] bxl --reuse-current-config [<extras>...] prelude//python/sourcedb/pyrefly.bxl:main @<argfile>
  • Type: list of strings
  • Default: none (the option is required)

repo_root

Path to the root of the repository.

  • Type: path
  • Default: none

permissive-ignores​

Should Pyrefly ignore errors based on annotations from other tools, e.g. # pyre-ignore or # mypy: ignore? By default, respects # pyrefly: ignore and # type: ignore. Enabling this option is equivalent to passing the names of all tools to enabled-ignores.

  • Type: bool
  • Default: false
  • Flag equivalent: --permissive-ignores

enabled-ignores​

What set of tools should Pyrefly respect ignore directives from? Passing the names of all tools is equivalent to enabling permissive-ignores.

  • Type: list of tools
  • Default: ["type", "pyrefly"]
  • Flag equivalent: --enabled-ignores

sub-config​

Override specific config values for matched paths in your project. See SubConfigs for more information on the structure and values that can be overridden here.

recursion-depth-limit​

warning

This is a debugging option for investigating stack overflow issues. You should only use this if Pyrefly is crashing with a stack overflow. If you encounter such a crash, please open an issue.

Maximum recursion depth before triggering overflow protection. When set to a non-zero value, Pyrefly will detect when type checking recursion exceeds this limit and handle it according to recursion-overflow-handler.

  • Type: integer
  • Default: 0 (disabled)
  • Flag equivalent: --recursion-depth-limit

recursion-overflow-handler​

warning

This is a debugging option. See recursion-depth-limit above.

How to handle when the recursion depth limit is exceeded:

  • "break-with-placeholder": Return a placeholder type and emit an internal error. Safe for IDE use.

  • "panic-with-debug-info": Dump debug information to stderr and panic. For debugging stack overflow issues.

  • Type: one of "break-with-placeholder", "panic-with-debug-info"

  • Default: "break-with-placeholder"

  • Flag equivalent: --recursion-overflow-handler

Configuration Details​

This section describes some of the configuration options, behaviors, or types in more depth, when there are details shared between multiple config options or the information is more than what can fit under a single config option description.

Environment Autoconfiguration​

Unless skip-interpreter-query is set, we'll attempt to query a Python interpreter to determine your python-platform or python-version if they're unset. We also get a site-package-path from your interpreter to determine which packages you have installed and append those to the end of any site-package-path you've configured yourself, either through CLI flags or a config file.

We look for an interpreter with the following logic:

  1. Use python-interpreter-path, fallback-python-interpreter-name](#fallback-python-interpreter-name), or [conda-environment` if any are set by a flag. More than one cannot be set in flags at the same time.
  2. Determine if there's an active venv or conda environment. If both are active at the same time, we take venv over conda.
  3. Use python-interpreter-path, fallback-python-interpreter-name](#fallback-python-interpreter-name), or [conda-environment` if either are set in a config file. Both cannot be set in a config at the same time.
  4. Find a venv at the root of the project by searching for something that looks like a Python interpreter (matches python(\d(\.\d+)?)?(.exe)? regex), and looking for a pyvenv.cfg file in known locations. If we can't determine the root of your project with a config file or other well-known root marker file (e.g. setup.py, pyrightconfig.json, mypy.ini), this step is skipped.
  5. Query $(which python3) and $(which python) (platform independent) to use a system-installed interpreter.
  6. Fall back to Pyrefly's default values for any unspecified config options.

The config options we query the interpreter for are:

  • python-platform: sys.platform
  • python-version: sys.version_info[:3]
  • site-package-path: site.getsitepackages() + [site.getusersitepackages()]
info

You can run pyrefly dump-config and pass in your file or configuration like you would with pyrefly check to see what Pyrefly finds for your Python interpreter and site-package-path, along with other useful config-debugging features.

Filesystem Globbing​

We use a standard Unix-style glob, which allows for wildcard matching when specifying a fileset. It is similar to regex, but more restricted given the subset of allowed syntax for paths on a filesystem. We currently only allow matching files with a .py, .pyi, or .pyw suffix.

The globs provided are relative to the config, if one is found, or the current working directory otherwise. Absolute path globs can also be provided, though this is generally not recommended, since it may not be compatible with other systems type checking your project.

  • We recognize the following wildcards:
    • * matches zero or more characters in a single directory component
    • ** matches the current and any sub directories/files in those sub directories
    • ? matches any one character
    • [<pattern>] matches any character or character range between the brackets (character range separated by -)
    • [!<pattern>] excludes any character or character range between the brackets and after the !
    • Note: [] can be used to match ?, *, [, ] literally (e.g. [?]), although these are invalid as part of a Python path.

We also support non-wildcard paths, so a relative (or absolute) path like src/ will match all Python files under src/ or src/my_file.py will match src/my_file.py exactly.

Any directories matched will also have their .py and .pyi files recursively matched. src/* will match all files and directories under src/, so therefore, we will recursively match everything under src/.

Examples:

  • src/**/*.py: only match .py files under src/
  • src, src/, src/*, src/**, and src/**/*: match all .py and .pyi files under `src/
  • ?.py and [A-z].py: match any file that looks like <letter>.py
  • src/path/to/my/file.py: only match src/path/to/my/file.py
  • src/**/tests, src/**/tests/, src/**/tests/**, and src/**/tests/**/*: match all .py and .pyi files in src/ under a directory named tests

Module Globbing​

In some config options, we've added globbing for module paths. This is different from both path globs and regex, in the sense that we're performing a match on a Python dotted import, such as this.is.any.module. The only wildcard we recognize is *, which represents zero or more segments of a module path, unless it starts a glob, in which case it must match one or more segments. The wildcard must be surrounded by ., unless it is at the start or end of a module glob.

Examples:

  • this.is.a.module would be equivalent to a regex like ^this\.is\.a\.module. It will only match imports that look like this.is.a.module.
  • this.is.*.module would become ^this\.is(\..+)*\.module$. It would match:
    • this.is.module
    • this.is.a.module
    • this.is.a.really.long.path.to.a.module
  • *.my.module would be equivalent to a regex like ^.+\.my\.module$.
    • It would match:
      • this.is.my.module
      • heres.my.module
    • It will not match:
      • my.module
  • this.is.* would be equivalent to a regex like ^this\.is(\..+)*. It would match:
    • this.is.my.module
    • this.is

Sub-Configs​

Sub-Configs are a method for overriding one or more config options for specific files based on filepath glob matching. Only certain config options are allowed to be overridden, and a need to override other configs means you likely need to use a separate config file for your subdirectory. You can have as many SubConfigs as you want in a project, and even multiple separate SubConfigs that can apply to a given file when the matches glob pattern matches.

SubConfig Allowed Overrides​

We currently allow the following config options to be overridden in a SubConfig:

  • errors
  • replace-imports-with-any
  • untyped-def-behavior
  • ignore-errors-in-generated-code

All SubConfig overrides replace the values appearing in the 'root' or top-level of the Pyrefly configuration.

Any configs that change the list of files we're type checking, Python environment, or where we look for imports cannot be included in SubConfigs. Some other configs we also do not include because we think they make it difficult to reason about your project type checks, but you can open an issue or make a pull request if you disagree and would like to see the option supported.

SubConfig Table Structure​

A SubConfig has two or more entries:

SubConfig Option Selection​

Since you can have more than one SubConfig matching a file, we need to define a resolution order to determine which SubConfig's option should be selected. Pyrefly does this by filtering SubConfigs whose matches does not match the given file, then takes the first non-null value that can be found in the order the SubConfigs appear in your configuration.

If no SubConfigs match, or there are no non-null config options present, then we take the value in the 'root'/top-level Pyrefly config (or Pyrefly default if no value is specified).

SubConfig Example​

For the following config, this how options would be resolved.

replace-imports-with-any = [
  "sympy.*",
  "*.series",
]
ignore-errors-in-generated-code = true

# disable `bad-assignment` and `invalid-argument` for the whole project
[errors]
bad-assignment = false
invalid-argument = false

[[sub-config]]
# apply this to `sub/project/tests/file.py`
matches = "sub/project/tests/file.py"

# any unittest imports will by typed as `typing.Any`
replace-imports-with-any = ["unittest.*"]

[[sub-config]]
# apply this config to all files in `sub/project`
matches = "sub/project/**"

# enable `assert-type` errors in `sub/project`
[sub-config.errors]
assert-type = true

[[sub-config]]
# apply this config to all files in `sub`
matches = "sub/**`

# disable `assert-type` errors in `sub`
[sub-config.errors]
assert-type = false

[[sub-config]]
# apply this config to all files under `tests` dirs in `sub/`
matches = "sub/**/tests/**"

# any pytest imports will be typed as `typing.Any`
replace-imports-with-any = ["pytest.*"]
  • sub/project/tests/file.py
    • replace-imports-with-any: ["unittest.*"]
    • errors: {assert-type = true}
    • ignore-errors-in-generated-code: true
  • sub/project/tests/another_file.py
    • replace-imports-with-any: ["pytest.*"]
    • errors: {assert-type = true}
    • ignore-errors-in-generated-code: true
  • sub/project/non_test_file.py
    • replace-imports-with-any: ["sympy.*", "*.series"]
    • errors: {assert-type = true}
    • ignore-errors-in-generated-code: true
  • sub/sub_file.py
    • replace-imports-with-any: ["sympy.*", "*.series"]
    • errors: {assert-type = false}
    • ignore-errors-in-generated-code: true
  • top_level_file.py
    • replace-imports-with-any: ["sympy.*", "*.series"]
    • errors: {assert-type = true, bad-assignment = false, invalid-argument = false}
    • ignore-errors-in-generated-code: true

Conda and Venv Support​

We plan on adding extra automatic support for Conda and Venv at some point soon, but we haven't made it around to doing this yet. If you would like to import packages from these in the meantime, you can follow the following steps.

Venv​

If you have a venv set up locally, you can get Pyrefly working with it by having your venv sourced in your shell (source .venv/bin/activate), and we will automatically pick up your installed packages. To pick up your packages even when your environment isn't sourced, you can add .venv/bin/python3 (or <path_to_venv>/bin/python3) to your Pyrefly configuration under python-interpreter-path or pass it in with the --python-interpreter-path flag.

Conda​

If you have conda set up locally, you can get Pyrefly working with it by having your Conda environment sourced in your shell (conda activate <environment>), and we will automatically pick up your installed packages. To pick up your packages even when your environment isn't sourced, you can query your environment's install location with conda env list, and add <conda_environment_path>/bin/python3 to your Pyrefly configuration under python-interpreter-path or pass it in with the --python-interpreter-path flag.

Example Configurations​

This section displays an example config showing the usage of all config options listed above to make creating your own easier, and to give you an easy place to start.

Default pyrefly.toml​

This is a configuration with the Pyrefly defaults. If you have an interpreter installed, some of these values may be overridden.

###### configuring what to type check and where to import from

# check all Python files under the containing directory
project-includes = ["**/*.py*"]
# exclude some uninteresting files
project-excludes = ["**/node_modules", "**/__pycache__", "**/*venv/**", "**/.[!/.]*/**"]
# perform an upward search for `.gitignore`, `.ignore`, and `.git/info/exclude`, and
# add those to `project-excludes` automatically
use-ignore-files = true
# import project files from "."
search-path = ["."]
# let Pyrefly try to guess your search path
disable-search-path-heuristics = false
# do not include any third-party packages (except those provided by an interpreter)
site-package-path = []

###### configuring your python environment

# assume we're running on linux, regardless of the actual current platform
python-platform = "linux"
# assume the Python version we're using is 3.13, without querying an interpreter
python-version = "3.13"
# is Pyrefly disallowed from querying for an interpreter to automatically determine your
# `python-platform`, `python-version`, and extra entries to `site-package-path`?
skip-interpreter-query = false
# query the default Python interpreter on your system, if installed and `python_platform`,
# `python-version`, or `site-package-path` are unset.
# python-interpreter-path = null # this is commented out because there are no `null` values in TOML

#### configuring your type check settings

# wildcards for which Pyrefly will unconditionally replace the import with `typing.Any`
replace-imports-with-any = []
# wildcards for which Pyrefly will replace the import with `typing.Any` if it can't be found
ignore-missing-imports = []
# should Pyrefly skip type checking if we find a generated file?
ignore-errors-in-generated-code = false
# what should Pyrefly do when it encounters a function that is untyped?
untyped-def-behavior = "check-and-infer-return-type"
# can Pyrefly recognize ignore directives other than `# pyrefly: ignore` and `# type: ignore`
permissive-ignores = false

[errors]
# this is an empty table, meaning all errors are enabled by default

# no `[[sub-config]]` entries are included, since there are none by default

Example pyrefly.toml​

project-includes = ["src"]
project-excludes = ["**/.[!/.]*", "**/tests"]
search-path = ["src"]
site-package-path = ["venv/lib/python3.12/site-packages"]

python-platform = "linux"
python-version = "3.12"
python-interpreter-path = "venv/bin/python3"

replace-imports-with-any = [
  "sympy.*",
  "*.series",
]
ignore-errors-in-generated-code = true

# disable `bad-assignment` and `invalid-argument` for the whole project
[errors]
bad-assignment = false
invalid-argument = false

[[sub-config]]
# apply this to `sub/project/tests/file.py`
matches = "sub/project/tests/file.py"

# any unittest imports will by typed as `typing.Any`
replace-imports-with-any = ["unittest.*"]

[[sub-config]]
# apply this config to all files in `sub/project`
matches = "sub/project/**"

# enable `assert-type` errors in `sub/project`
[sub-config.errors]
assert-type = true

Example pyproject.toml​

...

# Pyrefly header
[tool.pyrefly]

#### configuring what to type check and where to import from
project-includes = ["src"]
project-excludes = ["**/.[!/.]*", "**/tests"]
search-path = ["src"]
site-package-path = ["venv/lib/python3.12/site-packages"]

#### configuring your python environment
python-platform = "linux"
python-version = "3.12"
python-interpreter-path = "venv/bin/python3"

#### configuring your type check settings
replace-imports-with-any = [
  "sympy.*",
  "*.series",
]

ignore-errors-in-generated-code = true

[tool.pyrefly.errors]
bad-assignment = false
invalid-argument = false

[[tool.pyrefly.sub-config]]
# apply this config to all files in `sub/project`
matches = "sub/project/**"

# enable `assert-type` errors in `sub/project`
[tool.pyrefly.sub-config.errors]
assert-type = true

[[tool.pyrefly.sub-config]]
# apply this config to all files in `sub`
matches = "sub/**`

# disable `assert-type` errors in `sub/project`
[tool.pyrefly.sub-config.errors]
assert-type = false

# other non-Pyrefly configs
...

Exit Codes​

CodeMeaning
0Success - command completed without issues
1User error - command completed but problems (e.g., type errors) were found
3Infrastructure error - an error in the environment prevented the command from completing
101Panic - Pyrefly encountered an internal error and crashed