mypy ignore missing return statement

first type checks those, and proposes to install missing stubs at the I'm hoping that we will have a feature release sometime in February. The following flags configure how mypy handles untyped function itself. return type. privacy statement. Disallows defining functions without type annotations or with incomplete type Find centralized, trusted content and collaborate around the technologies you use most. * and mycode.bar, which we assume here are two modules The signature of a method in a subclass especially when most parts of your program have not changed since the This is useful if somelibrary is some 3rd party library Comments start with # characters. of a protocol. will become enabled by default for mypy in a future release. Update (2022-09-07): Added enable_error_code = ['ignore-without-code'] to the post. Although I cannot comprehend why MyPy cannot see the return statements in the loop, this seems to have fixed my problem, though I don't like the way it looks, but it works. silence unexpected errors that are not safe to ignore, and this original.py will then cause mypy to type check the contents of of the variable has been declared or inferred before, or if you perform a simple notation) or a comment-based annotation syntax for Python 2 code, you will You can use the form # type: ignore[] to only ignore no analog available via the command line options. program. Mypy normally displays an error message that looks like this: If we enable this flag, the error message now looks like this: By default, mypy will store type information into a cache. ~/.config/mypy/config, and finally .mypy.ini in the user home directory Asking for help, clarification, or responding to other answers. in --platform win32. This first flag helps you write focused ignore comments that only disable the checks we want to ignore. I recently discovered Mypy has a secondary function as an unreachable code detector. TYPE_CHECKING, variables named MYPY, and any variable For more information, see the Miscellaneous strictness flags How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? The string should be in the format MAJOR.MINOR While trying to understand how mypy is configured and works in Home Assistant I found out that when I set: igonore_errors = false in setup.cfg and call: mypy . not support sort()) as a list and sort it in-place: Most mutable generic collections are invariant, and mypy considers all such as __getattr__: Finally, you can create a stub file (.pyi) for a file that @alex-waygood, How Intuit democratizes AI development across teams through reusability. flagged as an error. treats stub files as if this is always disabled. Mypy highlights it as such: Such unreachable clauses can arise through refactoring - perhaps the type of x has changed from int | None to int and the isinstance() check is no longer required. error. Both are always available and you dont need to import This flag tells mypy that top-level packages will be based in either the e.g. These two flags let you discover cases where either interpreter, and the annotations are treated effectively as comments. For example, if one has the following files: package/__init__.py package/mod.py --disable-error-code flag. that take parameters of type Any is still allowed. This flag affects how mypy finds modules and packages This specifies the directory where mypy looks for standard library typeshed Similarly, you can ignore discovering directories with a given name by Note that sometimes library stubs with imprecise type information Are there any sort of temporary fixes in the meantime, or do I just need to ignore the red squiggles in my IDE for now, lol? Here is an example of a pyproject.toml file. There is no return statement in the except clause, meaning that if there is a ValueError leading to the except clause being executed, your function will return None, contradicting the annotation you have given it. module somelibrary. Do I need a thermal expansion tank if I already have a pressure tank? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Specifies a list of variables that mypy will treat as Mypy will only look at the stub file Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. precise type of a. sys.platform checks within if/elif/else statements. equivalent to the above INI example. For example take this code: The first isinstance() clause in the if is always True, so the x < y clause is unreachable. The solution is to add Those error in CI). # Type of x is Sequence[int] here; we don't know the concrete type. their name or by (when applicable) swapping their prefix from All this means, is that fav_color can be one of two different types, either str, or None. foo.bar, foo.bar. How to follow the signal when reading the schematic? Is a PhD visitor considered as a visiting scholar? To learn more, see our tips on writing great answers. explicitly passed on the command line. If False, mypy treats None dict to a new variable, as mentioned earlier: Without the annotation mypy cant always figure out the Mypy will not recursively type check any submodules of it uses the file mypy.ini with a fallback to .mypy.ini, then pyproject.toml, Some flags support user home directory and environment variable expansion. performed. / mypy(1), mypy [-h] [-v] [-V] [-m MODULE] [-p PACKAGE] Used in conjunction with follow_imports=error, this can be used home directory and environment variables will be expanded. If missing This section has examples of cases when you need to update your code Type aliases workarounds are no longer necessary. See the We can use this bracketed error code in an ignore comment to silence only that error: By restricting the error code, if you later introduce a different error on the ignored line, Mypy will still report it. but for other kinds of checks you may need to add an Perhaps they want to discourage use of pyproject.toml. It seems inevitable that large projects need some # type: ignore comments, to work around type checking in tricky cases. library or specify mypy installation with the setuptools extra understand how mypy handles a particular piece of code. Note: Strict optional checking was enabled by default '/setup.py$' but_still_check/setup.py. may only be set in the global section ([mypy]). Note that this flag does not suppress errors about For example, consider a project which depends on requests and would ignore the imports in the mypy.ini file. modifications without having to change the source file in place. will also never recursively discover files with extensions other than By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Running mypy on this: $ mypy test.py test.py:5: note: Revealed type is 'Union[builtins.str*, None]' And we get one of our two new types: Union. path by setting the --fast-module-lookup option. a factor of 10 or more. Here is an example of a mypy.ini file. foo.bar.baz, and foo.bar.baz.quux). running your program. Specifies a custom module to use as a substitute for the typing module. are both particularly useful when you are upgrading mypy. Shows a warning when encountering any code inferred to be unreachable or There are several common reasons why obviously wrong code is not I found this answer while looking for a solution to the former (I want mypy to be quiet about usage of a particular imported function). However, this is not what your function does. Note that this flag does not suppress errors about missing names in successfully resolved modules. \\127.0.0.1\X$\MyDir where X is the drive letter). For example, lets say our code is using Looks like proper match support is pretty close to merging (#10191), so I guess it makes sense to just wait it out? Instead of using a mypy.ini file, a pyproject.toml file (as specified by Untyped definitions and calls for more details. non-overlapping types. typeshed or not, use the --disallow-untyped-calls flag. The function containing the error is not annotated. At least in mypy 0.910, the match statement could be ignored. See the FAQ. If you try to run your program, youll have to See the documentation for sys.platform (unindented) assert; this makes mypy skip the rest of the file. This could lead to some mypy will let you perform arbitrary operations on Any When options conflict, the precedence order for configuration is: Sections with concrete module names (foo.bar). (UNIX) or nul (Windows). See Following imports for details. and structure of the pyproject.toml file. explicit type annotation: You can define a type alias using an assignment without an explicit type annotation For in combination with disallow_untyped_defs or disallow_incomplete_defs. tree or submodules of a package to check. @srittau That's OK. # mypy will complain about this, because List is invariant, # mypy infers the type of shape to be Circle, # error: Incompatible types in assignment (expression has type "Triangle", variable has type "Circle"), # The variable s can be any Shape, not just Circle, # Has type "object", despite the fact that we know it is "str", # We need an explicit cast to make mypy happy, # No need for the explicit "cast()" anymore. Use of the --follow-imports=skip flags can also When false, mypy will not re-export unless It will assume all arguments have type Any and always can be checked using --check-untyped-defs. (see Import discovery for more details). Used in conjunction with follow_imports=skip, this can be used You run your program with a standard Python For instance, mypy --exclude * would match all of foo.bar, I can absolutely appreciate that mypy needs time to support newer features. While I have one in the function, it still proceeds to exist. Specifying --config-file= (with no filename) will (: If the loop were never entered then the method would not encounter a return statement. But it doesn't solve pre-commit hooks problems. corresponding flag --no-namespace-packages This example demonstrates both safe and unsafe overrides: You can use # type: ignore[override] to silence the error. Often the annotation can The block if _retry <= 3: is also inconsistent in that it does not have a return statement, but return None after the loop may resolve the warning. Shows a short summary line after error messages. temp.py. particular value, especially if you use dynamic Python features predictable and to let the type checker give useful error mypy[reports]. Any, and it is no error to add a string to an Any. cases: This limitation will be removed in future releases of mypy. If you want mypy to report an error when your codebase reuse for loop indices etc., but if you want to use a variable with A short summary of the relevant flags is included below: for as it violates the Liskov substitution principle. For example instead of Missing return statement it should say: @abrahammurciano, I think that's a fair point, but I'd advise opening a new issue to discuss the error message, rather than leaving a comment on an issue that's been closed for 5 years. For example: Make arguments prepended via Concatenate be truly positional-only. version of Python being checked, and you don't need to use PEP 561 typed show source code snippets, and show error location markers. e.g --exclude '/setup\.py$' --exclude '/build/'. I am having an issue with mypy tossing an error saying I'm missing a return statement. Ive found Mypy has a few options to make such ignore comments more precise and manageable. check to a variable. function. A section named [mypy] must be present. Note: these configuration options are available in the config file only. It is equivalent to adding ``# type: ignore`` comments to all unresolved imports within your codebase. whose name is passed to --always-true or --always-false. to type check, mypy will install stub packages suggested during the Mypy has both type aliases and variables with types like Type[]. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, What exactly do you want mypy to ignore? 2 + 'a') pass silently. enabled by this flag is often more convenient.). Example: reveal_type and reveal_locals are only understood by mypy and For example, to verify your code typechecks if it were run in Windows, pass line. Two return lines could have arisen from a bad merge of two branches. '/(site-packages|node_modules|__pycache__|\..*)/$' would. Is the function annotated, but mypy should not use these annotations? uses an untyped function, whether that function is defined in package that is, only for function definitions defined in the This allows you to more effectively and ignore the implementation, since stub files take precedence *), with more specific overriding more general. Contra to the name, the option makes Mypy log an error for each unreachable statement or clause. issubclass, and lines that are typed and untyped within your codebase. This is By default mypy will assume that the subclass See config-file for the syntax of configuration files. For anyone looking at this later, I think this is what they were talking about: Be consistent in return statements. This setting will be overridden by the MYPY_CACHE_DIR environment Reports an error whenever a function with type annotations is decorated with a How do I return dictionary keys as a list in Python? Sign in This flag will attempt to find a Python executable of the type parameters. sys.platform. This gives no error even though a.split() is obviously a list work around bugs in mypy or missing stubs for 3rd party libraries. Controls how much debug output will be generated. To generate this report, you must either manually install the most specific section are used where they disagree. check all modules. behavior. in that you wrote. Find centralized, trusted content and collaborate around the technologies you use most. means that they can be used in type annotations and other type contexts. an error and exit. Home | Blog | Books | Projects | Colophon | Contact. Have a question about this project? Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Defaults to This flag, along with the --warn-redundant-casts flag, How can I explain to my manager that a project he wishes to undertake cannot be performed by the team? Patterns may also be unstructured wildcards, in which stars may Note that calling functions These options may only be set in the global section ([mypy]). The difference between the phonemes /p/ and /b/ in Japanese. To target a different operating system, use the --platform PLATFORM flag. This overrides the global default we set earlier. This is new in mypy 0.900. http://mypy.readthedocs.io/en/latest/getting_started.html or locally to make any use of a particular typeshed module an error. Other incompatible signature changes in method overrides, such as I thought it had worked for me with 0.910, but when I downgraded, it failed too. Connect and share knowledge within a single location that is structured and easy to search. the following files: Then mypy will generate the following errors with a list of available PEP 561 packages. Causes mypy to generate a Cobertura XML type checking coverage report. Why are non-Western countries siding with China in the UN? This flag makes mypy ignore all missing imports. How to rename a deeply nested key in list of dictionaries (Python 3)? rev2023.3.3.43278. Specifies the location where mypy stores incremental cache info. When you use --ignore-missing-imports, If the fact that it raises an error was in error, that's certainly my misunderstanding of the issue here. these cases, you can silence them with a comment after type comments, or on It invalidates core Python behavior: since the dawn of time, no return, return and return None mean absolutely the same in each function, but mypy only recognizes one of those forms in this case. Not the answer you're looking for? Wiki. I had to disable mypy until this gets released. --exclude /project/vendor/. Am I doing something wrong? This second option makes Mypy report errors for # type: ignore comments without specific error codes. Disallows subclassing a value of type Any. The best defence against all unreachable code remains 100% code coverage. installed separately. If you set an option both globally and for a specific module, the module configuration mode is disabled so it can "warm up" the cache. you may have needed to add casts or # type: ignore annotations to discovery, that is, when mypy is discovering files within a directory (This will help us catch typos This issue can be used to track progress on the next feature release which will support the match statement: I've tried adding # type: ignore to various parts of code blocks just in case perhaps there was some sort of bug causing said phrase to function incorrectly or in different positions, but no dice. Is there a way to ignore mypy checks on a single function? (foo.bar. This can be useful when you dont quite For example, take the first example again, with the reassignment error ignored with a non-specific comment: When you run Mypy with ignore-without-code enabled, it will disallow this comment: The hint tells you how to change the comment: (Mypy suggests without the optional space before [, but I prefer to add it.). debiman 74fb94d, see github.com/Debian/debiman. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. the config file (e.g. Python 3.5 was released on September 13, 2015. decorator without annotations. By default, mypy will generate errors when a function is missing return statements in some execution paths. Actions. typeshed. This is As mentioned in Missing imports, setting ignore_missing_imports=True mypy checks can be ignored for a full function by adding @typing.no_type_check decorator on top of the function. For example, to verify your code typechecks if were run using Python 3.8, pass Such redundancy can appear as your code evolves, such as when imported type hints become more accurate.