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https://github.com/ambv/flake8-mypy

A plugin for flake8 integrating Mypy.
https://github.com/ambv/flake8-mypy

flake8 linter linter-plugin mypy plugin type-hints typing

Last synced: 3 months ago
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A plugin for flake8 integrating Mypy.

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README 

        
# flake8-mypy



## NOTE: THIS PROJECT IS DEAD



It was created in early 2017 when Mypy performance was often insufficient for

in-editor linting. The Flake8 plugin traded correctness for performance,

making Mypy only check a bare minimum of problems. These days Mypy is

accelerated with mypyc, as well as uses aggressive caching to speed up

incremental checks. It's no longer worth it to use hacks such as flake8-mypy.



## What was the project anyway?



A plugin for [Flake8](http://flake8.pycqa.org/) integrating

[mypy](http://mypy-lang.org/). The idea is to enable limited type

checking as a linter inside editors and other tools that already support

*Flake8* warning syntax and config.



## List of warnings



*flake8-mypy* reserves **T4** for all current and future codes, T being

the natural letter for typing-related errors.  There are other plugins

greedily reserving the entire letter **T**.  To this I say: `¯\_(ツ)_/¯`.



**T400**: any typing note.



**T484**: any typing error (after PEP 484, geddit?).



**T498**: internal *mypy* error.



**T499**: internal *mypy* traceback, stderr output, or an unmatched line.



I plan to support more fine-grained error codes for specific *mypy*

errors in the future.



## Two levels of type checking



*mypy* shines when given a full program to analyze.  You can then use

options like `--follow-imports` or `--disallow-untyped-calls` to

exercise the full transitive closure of your modules, catching errors

stemming from bad API usage or incompatible types.  That being said,

those checks take time, and require access to the entire codebase.  For

some tools, like an editor with an open file, or a code review tool,

achieving this is not trivial.  This is where a more limited approach

inside a linter comes in.



*Flake8* operates on unrelated files, it doesn't perform full program

analysis.  In other words, it doesn't follow imports.  This is a curse

and a blessing.  We cannot find complex problems and the number of

warnings we can safely show without risking false positives is lower.

In return, we can provide useful warnings with great performance, usable

for realtime editor integration.



As it turns out, in this mode of operation, *mypy* is still able to

provide useful information on the annotations within and at least usage

of stubbed standard library and third party libraries.  However, for

best effects, you will want to use separate configuration for *mypy*'s

standalone mode and for usage as a *Flake8* plugin.



## Configuration



Due to the reasoning above, by default *flake8-mypy* will operate with

options equivalent to the following:



```ini

[mypy]

# Specify the target platform details in config, so your developers are

# free to run mypy on Windows, Linux, or macOS and get consistent

# results.

python_version=3.6

platform=linux



# flake8-mypy expects the two following for sensible formatting

show_column_numbers=True

show_error_context=False



# do not follow imports (except for ones found in typeshed)

follow_imports=skip



# since we're ignoring imports, writing .mypy_cache doesn't make any sense

cache_dir=/dev/null



# suppress errors about unsatisfied imports

ignore_missing_imports=True



# allow untyped calls as a consequence of the options above

disallow_untyped_calls=False



# allow returning Any as a consequence of the options above

warn_return_any=False



# treat Optional per PEP 484

strict_optional=True



# ensure all execution paths are returning

warn_no_return=True



# lint-style cleanliness for typing needs to be disabled; returns more errors

# than the full run.

warn_redundant_casts=False

warn_unused_ignores=False



# The following are off by default since they're too noisy.

# Flip them on if you feel adventurous.

disallow_untyped_defs=False

check_untyped_defs=False

```



If you disagree with the defaults above, you can specify your own *mypy*

configuration by providing the `--mypy-config=` command-line option to

*Flake8* (with the .flake8/setup.cfg equivalent being called

`mypy_config`). The value of that option should be a path to a mypy.ini

or setup.cfg compatible file.  For full configuration syntax, follow

[mypy documentation](http://mypy.readthedocs.io/en/latest/config_file.html).



For the sake of simplicity and readability, the config you provide will

fully replace the one listed above.  Values left out will be using

*mypy*'s own defaults.



Remember that for the best user experience, your linter integration mode

shouldn't generally display errors that a full run of *mypy* wouldn't.

This would be confusing.



Note: chaing the `follow_imports` option might have surprising effects.

If the file you're linting with Flake8 has other files around it, then in

"silent" or "normal" mode those files will be used to follow imports.

This includes imports from [typeshed](https://github.com/python/typeshed/).



## Tests



Just run:



```

python setup.py test

```



## OMG, this is Python 3 only!



Yes, so is *mypy*.  Relax, you can run *Flake8* with all popular plugins

**as a tool** perfectly fine under Python 3.5+ even if you want to

analyze Python 2 code.  This way you'll be able to parse all of the new

syntax supported on Python 3 but also *effectively all* the Python 2

syntax at the same time.



By making the code exclusively Python 3.5+, I'm able to focus on the

quality of the checks and re-use all the nice features of the new

releases (check out [pathlib](https://docs.python.org/3/library/pathlib.html))

instead of wasting cycles on Unicode compatibility, etc.



## License



MIT



## Change Log



### 17.8.0



* avoid raising errors in the default config which don't happen during

  a full run (disable warn_unused_ignores and warn_redundant_casts)



* always run type checks from a temporary directory to avoid

  clashing with unrelated files in the same directory



### 17.3.3



* suppress *mypy* messages about relative imports



### 17.3.2



* bugfix: using *Flake8* with absolute paths now correctly matches *mypy*

  messages



* bugfix: don't crash on relative imports in the form `from . import X`



### 17.3.1



* switch `follow_imports` from "silent" to "skip" to avoid name clashing

  files being used to follow imports within

  [typeshed](https://github.com/python/typeshed/)



* set MYPYPATH by default to give stubs from typeshed higher priority

  than local sources



### 17.3.0



* performance optimization: skip running *mypy* over files that contain

  no annotations or imports from `typing`



* bugfix: when running over an entire directory, T484 is now correctly

  used instead of T499



### 17.2.0



* first published version



* date-versioned



## Authors



Glued together by [Łukasz Langa](mailto:[email protected]).