Type hint checker

Checks that the parameters in functions and methods have type hints. Type hint checker is intended to be used as a pre-commit hook.

def f1(a):
    pass

> git commit 
type_hint_checker.......................................................Failed
    - hook id: type_hint_checker
    - duration: 0.33s
    - exit code: 1
    
    INFO:type_hint_checker:test.py: Missing type hint for parameter a (function f1), line 1
    INFO:type_hint_checker:test.py: Missing return type hint for function f1, line 1

Quick start

1. Install pre-commit hooks https://pre-commit.com/#install

   pip install pre-commit

2. Create a .pre-commit-config.yaml or use your existing config file. Add the following lines:

   repos:
   -   repo: https://github.com/PaulinaPacyna/type-hint-checker
       rev: latest
       hooks:
       - id: type_hint_checker
         name: type_hint_checker
         description: Check that all python functions have type hints
         entry: type_hint_checker
         language: python
         verbose: true
         files: ".py$"
         args: [
           #--exit_zero, # always exit with 0 code
           #--exclude_files=tests, #exclude all paths that have the string tests inside
           #--exclude_parameters=^self$, #don't throw warnings about self parameter
        ]

3. Install the pre-commit hook

   pre-commit install
   

4. Commit a file

    echo  'def f1(a): pass' > test.py
    git commit test.py -m "Test type_hint_checker pre-commit hook"

   The output should be similar to this:

    type_hint_checker.......................................................Failed
    - hook id: type_hint_checker
    - duration: 0.33s
    - exit code: 1
    
    INFO:type_hint_checker:test.py: Missing type hint for parameter a (function f1), line 1
    INFO:type_hint_checker:test.py: Missing return type hint for function f1, line 1
   

Run type hint checker from terminal

0. If you already have it installed in pre-commit hooks:

   pre-commit run type_hint_checker --all-files
   

1. Try the cli version out by running

   pip install type_hint_checker

2. Run the tool using

   type_hint_checker <path to file>

   or

   python -m type_hint_checker <path to file>

Arguments

It is understandable that there are different coding standards. You can customize the behavior of this pre-commit hook by adding the following options to your .pre-commit-config.yaml.

Argument	Usage	Default value	Example values
--exit_zero	If this flag is checked, the program always exits with 0 (success) code. It is strongly advised to use this flag together with verbose: true option in pre-commit options.	Not checked by default.	Either add "--exit_zero" to the args or don't.
--exclude_files	Regex specifying which files should not be checked.	Empty (all files are checked)	"--exclude_files=^test_"
--exclude_parameters	Regex specifying which parameters should not be checked.	^self$	"--exclude_parameters=''" (check all params) "--exclude_parameters='(^self$|logger)'"
--exclude_by_name	Regex specifying names of functions, methods and classes that should not be checked	Empty (all functions, classes and methods are checked).	"--exclude_by_name='^test_'"
--log-level	If set to DEBUG, displays more logs.	INFO	"--log-level=INFO","--log-level=DEBUG"
--ignore_comment	You can change the content of the comment that disables checking a given function or method. By default #no-check excludes the item from being checked. See below for more info.	no-check	"--ignore_comment='hint-no-check'"

If you have troubles setting those values, it may be due to how your system parses special characters in command line options. Add --log-level=DEBUG to you .pre-commit-config.yaml. The log message will show you what values are passed as command line arguments.

DEBUG:type_hint_checker:{'filenames': ['test.py'],
 'exit_zero': False, 
'exclude_files': 'tests/', 
'exclude_parameters': '^self$', 
'exclude_by_name': '', 
'log_level': 'DEBUG', 
'ignore_comment': 'no-check'}

Disable warnings

If you find type_hint_checker too restrictive, you are welcome to adjust its behavior. You can choose to ignore whole files, functions, parameters or single lines

Ignore a path

If you don't want to check a certain file or folder, add the path to the --exclude_files argument. The argument must be a valid regex. To omit checking the directory tests/ and the file setup.py use the following regex in your .pre-commit-config:

args: ["--exclude_files='(tests/|setup.py)'" ]

Ignore a function by name

You can disable checking functions that are named in a certain way. To disable checking all functions that begin with test_ prefix, use:

args: ["--exclude_by_name='^test_" ]

Then, for example this signature won't throw a warning:

def test_filepath_in_log(caplog):
    ...

Ignore a parameter by name

You can disable checking parameters with a regex, e.g. the self parameter

args: [ --exclude_parameters=^self$ ]

With the option shown above, this method signature won't throw any warnings:

class FileMaker:
    def read_file(self) -> str:
        ...

With a comment

In special cases, you can just put #no-check comment next to the function, and the function will be omitted by this pre-commit hook.

def func(a: int, b: int, n): #no-check
    pass

The pre-commit hook will not warn you about the missing type hint for the return and parameter n. You can customize the comment content using --ignore_comment option.

In case of fire

You can always commit without any pre-commit checks using

git commit --no-verify

Pep8 specification about type hints

The default formatting options were set in accordance to PEP8 484

Tests

To run the tests, run

python -m pytest tests/