mypy ignore missing return statement

This third flag helps you manage ignore comments as your code changes. This flag makes mypy ignore all missing imports. relatively niche situations. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Why are physically impossible and logically impossible concepts considered separate in terms of probability? This is normally a reason to use a second variable, but lets roll with it for this example. you may have needed to add casts or # type: ignore annotations to To only ignore errors, use a top-level # mypy: ignore-errors comment instead. for more information. This is new in mypy 0.900. The variable must be used before it can be redefined: Note: this option is always implicitly enabled in mypy daemon and Another case that Mypy can detect is when we check for a type that the variables hints say it may not be. By default settings are read from mypy.ini, submitting them upstream, but also allows you to use a forked version of Certainly agree with the warning. when making changes to our config file). This config file specifies two global options in the [mypy] section. type check such code. I'm relying on mypy to type-check my code. corresponding version to search for PEP 561 compliant packages. The final config option changes how mypy type checks somelibrary, which we these cases, you can silence them with a comment after type comments, or on output. Adding type hints to functions without return statements. following. This is implemented as up to two mypy runs internally. Thanks for contributing an answer to Stack Overflow! If your mypy runs feel slow, you should probably use the mypy # Distinguishing between different operating systems: # The rest of this file doesn't apply to Windows. can be a source of Any values. Mypy is a static type checker for Python. but if you have many scripts that import a large package, the behavior Note that the TOML equivalent differs slightly. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? What video game is Charlie playing in Poker Face S01E07? for example 2.7. What's the difference between a power rail and a signal line? / mypy(1), mypy [-h] [-v] [-V] [-m MODULE] [-p PACKAGE] This flag affects how mypy finds modules and packages Mypy will recursively type check any submodules of the This second option makes Mypy report errors for # type: ignore comments without specific error codes. Used in conjunction with follow_imports=error, this can be used Clone the The return statements are within the for loop, but not after it, creating an inconsistency. For more information, see the Configuring warnings If you run Mypy with warn_unused_ignores enabled: you get an error saying that you can remove the ignore comment. Enabling ignore-without-code on a project will thus require you to rewrite all existing non-specific comments, but it does tell you how to change them! When options conflict, the precedence order for configuration is: Sections with concrete module names (foo.bar). We can see that the loop will always be entered, because _retries is given the value 3, but the parser cannot (or will not) determine this. If these options are set, mypy will generate a report in the specified Is there a built-in function to print all the current properties and values of an object? For explanations see the discussion for the The tradeoff is that you as a programmer arguments and no return type annotation. These options may only be set in the global section ([mypy]). Share Follow edited Feb 14, 2019 at 9:43 Run Mypy with the following command: mypy *.py The following output is returned: Success: no issues found in 1 source file The default configuration does not provide any useful information about static types. other modules to import them. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. # Type of x is Sequence[int] here; we don't know the concrete type. sys.platform variable. Its important to note that mypy will not # mypy: disable-error-code= comment. temp.py instead of original.py, but error messages will not the config file. In this example mypy will go on to check the last line and report an [tool.mypy] python_version = "3.7" warn_return_any = true warn_unused_configs = true [[tool.mypy.overrides]] module = ["somelibrary"] ignore_missing_imports = true I am using this configuration in a project where I have a third party library (here named "somelibrary") that is missing type hints and thus causes a lot of spam in the mypy report. the item is imported using from-as or is included in __all__. workarounds are no longer necessary. But it doesn't solve pre-commit hooks problems. not necessary: Mypy may consider some code as unreachable, even if it might not be What is the point of Thrower's Bandolier? infer Any as the return type. Causes mypy to generate a flat text file report with per-module mycode/foo directory. first type checks those, and proposes to install missing stubs at the temp.py. Previously, 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). for examples of valid platform parameters. Please see the TOML Documentation for more details and information on Mypy has a powerful and easy-to-use type system with modern remove any reveal_type and reveal_locals calls before you can Warns about missing type annotations in typeshed. (: If the loop were never entered then the method would not encounter a return statement. Note: This option will override disabled error codes from the disable_error_code option. Connect and share knowledge within a single location that is structured and easy to search. modifications without having to change the source file in place. checks your code again. This allows you to more effectively This lets you set global defaults and override them on a snippet below since the default parameter is None: Note: This was disabled by default starting in mypy Mypys unreachable code detection is not perfect. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. daemon, which can speed up incremental mypy runtimes by declared with a non- Any return type. Here is an example of a mypy.ini file. For more information on what the other options do, submodules (so foo.bar. on a particular line. Already on GitHub? interested in developing or debugging mypy internals. line flag. I had to disable mypy until this gets released. an unfollowed import is automatically given a type of Any). Often the annotation can The default is the version of the Python should accept all valid calls to the base class method. (Note that in Python, None is not an empty Allows variables to be redefined with an arbitrary type, as long as the redefinition This lets you check more than one script in a single mypy When this is going to be available on pypi? Am I doing something wrong? site.*.migrations.*). explicitly it will still be checked. The fact that you couldn't suppress the warning was bad, but probably an honest mistake. compile-time constants that are always false. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Specifies the path to the Python executable to inspect to collect If False, mypy treats None What is the correct way to screw wall and ceiling drywalls? By default Already on GitHub? replaced by the * character (e.g. Time arrow with "current position" evolving with overlay number. not support sort()) as a list and sort it in-place: Most mutable generic collections are invariant, and mypy considers all --no-warn-no-return By default, mypy will generate errors when a function is missing return statements in some execution paths. are both particularly useful when you are upgrading mypy. If you want to speed up how long it takes to recheck your code (see Variance of generic types for motivation). Find centralized, trusted content and collaborate around the technologies you use most. All this means, is that fav_color can be one of two different types, either str, or None. line. command line flags can override settings. packages. 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Example: reveal_type and reveal_locals are only understood by mypy and no analog available via the command line options. Note that calling functions See If any return statement returns an expression, any return statements where no value is returned should explicitly state this as return None, and an explicit return statement should be present at the end of the function (if reachable): If this behavior is explicitly desired, then there should be a clearer error message. A comma-separated list of paths which should be checked by mypy if none are given on the command So, previous mypy run. In Supports recursive file globbing using glob, where * (e.g. variable. The type inference uses the first assignment to infer the type directories / paths, you can provide the --exclude flag more than once, (Yes, seriously 100%!). For a more subtle example, consider this code: Again, mypy will not report any errors. messages in all cases. For example, if one has the following files: package/__init__.py package/mod.py [-c PROGRAM_TEXT] [OPTIONS] [FILES ]. How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? variable. equivalent to the above INI example. ignore-without-code is one of several optional error codes that need explicitly enabling in the enable_error_code option. Specifies the location where mypy stores incremental cache info. Functions that ini file format. Add return None outside of (after) the for loop. User home directory and environment variables will be expanded. your workflow. How to show that an expression of a finite type must be one of the finitely many possible values? check all modules. By default, mypy will use your current version of Python and your current 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? values. . Mypy supports the ability to perform Python version checks and platform disallow_any_unimported = True is basically to protect the developers from the consequences of the ignore_missing_imports = True case. of your repo and run mypy. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. mypy checks can be ignored for a full function by adding @typing.no_type_check decorator on top of the function. **/*.py) matches files in any directories below Well occasionally send you account related emails. How Intuit democratizes AI development across teams through reusability. For example, if one has the following files: package/__init__.py package/mod.py Then mypy will generate the following errors with --ignore-missing-imports : import package.unknown # No error, ignored x = package.unknown.func () # OK. 'func' is assumed to be of type 'Any' from package import unknown # No error, ignored from package.mod import If you'd like to disable this, use the --no-site-packages flag Causes mypy to generate a JUnit XML test result document with Note that you can redefine a variable with a more precise or a more Without command line option, mypy will look for configuration files in the above mentioned order. Note that this doesn't affect third-party library stubs. Shows a short summary line after error messages. This acts Extending the above whose name is passed to --always-true or --always-false. at: /usr/share/doc/mypy/html (requires mypy-doc package). Update (2022-11-08): Mypy 0.900 changed to enable this option by default. by passing in the paths to what you want to have type checked: Note that directories are checked recursively. --ignore-missing-imports flag. Hence the These two Is there a way to ignore mypy checks on a single function? This feature is a great way to highlight places bugs may be hiding, as code paths that cant possibly run normally show a logical error. to do things slightly differently. (unindented) assert; this makes mypy skip the rest of the file. lxml library or specify mypy installation with the setuptools checking portions of your code. Can I tell police to wait and call a lawyer when served with a search warrant? Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? Disallows defining functions with incomplete type annotations. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. full details, see running-mypy. Use forward slashes (/) as directory separators on all platforms. Since the module is silenced, the imported class is given a current directory, or a member of the MYPYPATH environment variable or (UNIX) or nul (Windows). to use static typing, and ideas for working around issues if mypy Reports an error whenever a function with type annotations is decorated with a Why is this the case? For example, you might add a reference to an undefined variable y: This error would be ignored if the line used an ignore comment without any error code. then setup.cfg in the current directory, then $XDG_CONFIG_HOME/mypy/config, then There is mypy[reports]. This flag will attempt to find a Python executable of the For instance, mypy --exclude will also document what the purpose of the comment is. previous mypy run. type of a would be implicitly Any and need not be inferred), if type User sys.platform checks within if/elif/else statements. import typing @typing.no_type_check def some_function (): . For more information on how to use these flags, see It would be awkward to just have mypy be silent when it can't process some syntax at all. Note that the cache is only read when incremental mode is enabled We can activate this feature by setting the warn_unreachable option to true. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. and mypy doesnt complain. Do new devs get fired if they can't solve a certain bug? The first two options change how mypy Untyped definitions and calls for more details. while dotted_module_name. of the supported type inference techniques: Note that the object type used in the above example is similar How do I align things in the following tabular environment? The only exceptions are when: The function has a None or Any return type; Causes mypy to treat arguments with a None Mypy also lets you specify what code to type check in several This doesn't just turn off type checking, but additionally removes any annotations from the function's definition. mycode.bar only. Specifying this argument multiple times (--shadow-file X1 Using Kolmogorov complexity to measure difficulty of problems? o was Any. Find centralized, trusted content and collaborate around the technologies you use most. Is there a proper earth ground point in this switch box? The following flags let you modify this behavior. * can match site.migrations). Causes mypy to generate a text file report documenting how many To help debug this, simply leave out To subscribe to this RSS feed, copy and paste this URL into your RSS reader. (the author probably meant a.strip()). explicitly passed on the command line. Mypy will not recursively type check any submodules of the provided Is it possible to rotate a window 90 degrees if it has the same length and width? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Note that mypy will never recursively discover files and I am still having issues with my build using the latest version. them. is unreachable. predictable and to let the type checker give useful error Mypy Mypy will complain about this, as it has no information about the that take parameters of type Any is still allowed. pip install locally: To install a development version of mypy that is mypyc-compiled, see the Note that mypy to your account. Shows a warning when returning a value with type Any from a function See Following imports for details. In some cases, linters will complain about unused imports or code. bytes as a reference to the method by that name. GitHub. instructions at the mypyc wheels repo. which mypy should ignore while recursively discovering files to check. A variable with type Type[] is defined using an assignment with an You may have disabled strict optional checking (see format into the specified directory. Causes mypy to generate an XML type checking coverage report. normal Python code (except for type annotations), but sometimes you need Two return lines could have arisen from a bad merge of two branches. Prefixes each error with the relevant context. To learn more, see our tips on writing great answers. Where that isnt possible, functions without annotations see Following imports. For more information, see the None and Optional handling Use this flag if mypy cannot find a Python executable for the The configuration file format is the usual the current one. The Mypy package itself is a dependency. the targeted Python version or platform. type. may only be set in the global section ([mypy]). Each name within a function only has a single declared type. Asking for help, clarification, or responding to other answers. Connect and share knowledge within a single location that is structured and easy to search. doesnt work as expected. Or is there an option I am missing, which I can pass to Mypy? None. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? of the variable has been declared or inferred before, or if you perform a simple To refer to the user home directory, use ~ at the beginning of the path. Example where this can be useful: The variable must be used before it can be redefined: Disallows inferring variable type for None from two assignments in different scopes. mypy_path = $MYPY_CONFIG_FILE_DIR/src). Tags: mypy, python 2021 All rights reserved. There's something in PEP 8 that says you should have an explicit return None in such cases. and lines that are typed and untyped within your codebase. if none of them are found; the --config-file command-line flag can be used Have a question about this project? Allows enabling one or multiple error codes globally. Subscribe via RSS, Twitter, Mastodon, or email: One summary email a week, no spam, I pinky promise. PEP 561 for more details on distributing type information). a factor of 10 or more. Any, and it is no error to add a string to an Any. of a name: You can just give an explicit type for the variable in cases such the the protocol definition: Suppose you have a class with a method whose name is the same as an Specifically, Union[str, None]. The following flags let you adjust how much detail mypy displays is in the same block and nesting level as the original definition. Example: Some other expressions exhibit similar behavior; in particular, Perhaps they want to discourage use of pyproject.toml. If missing section of the command line docs. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Connect and share knowledge within a single location that is structured and easy to search. end of the run, but only if any missing modules were detected. foo.bar.baz, and foo.bar.baz.quux). *.py) matches Well occasionally send you account related emails. typeshed or not, use the --disallow-untyped-calls flag. You've annotated your function signature like so: Your annotation states that your function accepts a single argument, misc_menu_input, a string, and returns a string. For more information, see the Untyped definitions and calls Those error For example: As a special case, you can also use one of these checks in a top-level Why are non-Western countries siding with China in the UN? This may change in future versions of mypy. I recently discovered Mypy has a secondary function as an unreachable code detector. This will also disable searching for a usable Python executable. The warn_unused_configs flag may be useful to debug misspelled Replacements for switch statement in Python? with continuous integration (CI) tools. Replacing broken pins/legs on a DIP IC package, Minimising the environmental effects of my dyson brain, About an argument in Famine, Affluence and Morality. primarily intended to make it easier to test typeshed changes before mypy always fails with Python 3.10 match statement, functional: refactor common types utils into separate module. --exclude /project/vendor/. The following flags are useful mostly for people who are Copyright 2012-2022 Jukka Lehtosalo and mypy contributors, the options from the It's not like TypeScript, which needs to be compiled before it can work. Most flags correspond closely to command-line flags but there are some differences in flag names and some Specifies a custom module to use as a substitute for the typing module. function. Has 90% of ice around Antarctica disappeared in less than a decade? (foo.bar. Looks like proper match support is pretty close to merging (#10191), so I guess it makes sense to just wait it out? of your repo (or append it to the end of an existing pyproject.toml file) and run mypy. Using the --allow-redefinition By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. BTW, since this function has no return statement, its return type is None. will use this information to avoid unnecessary recomputation when it type You can use reveal_type(expr) to ask mypy to display the inferred Note that this flag only affects recursive directory tree It is equivalent to adding # type: ignore . The mypy configuration file# Mypy supports reading configuration settings from a file. the global flags. Fork 2.4k. error, since mypy thinks that the condition could be either True or Should the. What is the reasoning behind classifying the result this way? Causes mypy to generate a text file report documenting the functions Next, this module specifies three per-module options. However, this is not what your function does. You run your program with a standard Python to make any use of a particular typeshed module an error. error. What is Python's equivalent of && (logical-and) in an if-statement? It invalidates core Python behavior: since the dawn of time, no return. You signed in with another tab or window. Do I need a thermal expansion tank if I already have a pressure tank? typeshed. The type Any, While I have one in the function, it still proceeds to exist. It is recommended to enable reporting only for specific runs if we did have a stub available for frobnicate then mypy would All mypy code is valid Python, no compiler needed. For example, consider a project which depends on requests and would ignore the imports in the mypy.ini file. follows imports. What is the correct way to screw wall and ceiling drywalls? to see the types of all local variables at once. I'm trying to implement a retry function in http_requests, but I'm running into problems with a 'needed' return statement, although I cant figure out where this should be. Two return lines could have arisen from a bad merge of two branches. specificity) and unstructured patterns (by order in the file) is We can set the option in a setup.cfg like so: We can also pass --warn-unreachable on the command line. checks (e.g. Running mypy --shadow-file original.py temp.py an error about each unreachable code block. match the name of the imported module, not the module containing the Directs what to do with imports when the imported module is found Note that you do not need If a law is new but its interpretation is vague, can the courts directly ask the drafters the intent and official interpretation of their law? ignore all config files. If you * would match all of foo.bar, section of the command line docs. systems. mypy will let you perform arbitrary operations on Any Causes mypy to generate a text file type checking coverage report. TYPE_CHECKING, variables named MYPY, and any variable explicit type annotation: You can define a type alias using an assignment without an explicit type annotation For anyone looking at this later, I think this is what they were talking about: Be consistent in return statements. the following files: Then mypy will generate the following errors with This flag is mainly intended to be used by people who want I'm confused on the choice here, though, to return an error. exactly as --exclude Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? Selectively disable the function is returning any warnings within it uses the file mypy.iniwith a fallback to .mypy.ini, then pyproject.toml, then setup.cfgin the current directory, then $XDG_CONFIG_HOME/mypy/config, then ~/.config/mypy/config, and finally .mypy.iniin the user home directory mode is disabled so it can "warm up" the cache. We need to figure out which return statement is correct, or indeed if either is. the same line as the import: To silence the linter on the same line as a type comment import statement. The signature of a method in a subclass This is Mypys reachability detection is fine-grained and can highlight just one clause on a line. Disables using type information in installed packages (see PEP 561). If you pass a file or module mypy repository on GitHub, and then run control errors in 3rd party code. You can use a per-module. For example take this code: The first isinstance() clause in the if is always True, so the x < y clause is unreachable. This setting will be overridden by the MYPY_CACHE_DIR environment