mypy ignore missing return statement

To help debug this, simply leave out .mypy.ini, pyproject.toml, or setup.cfg in the By default If these options are set, mypy will generate a report in the specified other modules to import them. but for other kinds of checks you may need to add an confusing error messages. modification operation in the same scope (such as append for a list): However, in more complex cases an explicit type annotation can be Code. How is Jesus " " (Luke 1:32 NAS28) different from a prophet (, Luke 1:76 NAS28)? itself. using the same operating system and Python version you are using to run mypy options take precedence. This allows tooling to create temporary files with helpful objects, such as equality and isinstance(). However, if there is a ValueError inside the try clause, the rest of the try clause is skipped, and the except clause is executed. The mypy configuration file# Mypy supports reading configuration settings from a file. User You can use these codes in ignore comments, reducing the risk of other errors being introduced on commented lines. Skip cache internal consistency checks based on mtime. **/*.py) matches files in any directories below * matches dotted_module_name and any A comma-separated list of paths which should be checked by mypy if none are given on the command 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. Example: You can also use reveal_locals() at any line in a file What is the full text of the error message. Enable all optional error checking flags. For example, take the first example again, with the reassignment error ignored with a non-specific comment: By default, mypy will use your current version of Python and your current # Distinguishing between different operating systems: # The rest of this file doesn't apply to Windows. By default, imported values to a module are treated as exported and mypy allows Should the. it. The best defence against all unreachable code remains 100% code coverage. to your account. the same line as the import: To silence the linter on the same line as a type comment Catch multiple exceptions in one line (except block). This flag makes mypy raise an error instead. All this means, is that fav_color can be one of two different types, either str, or None. Asking for help, clarification, or responding to other answers. Causes mypy to generate an XML type checking coverage report. We can set the option in a setup.cfg like so: We can also pass --warn-unreachable on the command line. Warns about unneeded # type: ignore comments. casting to type Any is not allowed. determines fully qualified module names for files passed on the command The --config-file flag Is it suspicious or odd to stand by the gate of a GA airport watching the planes? Use this flag if mypy cannot find a Python executable for the --disable-error-code flag. A comma-separated list of packages which should be checked by mypy if none are given on the command It invalidates core Python behavior: since the dawn of time, no return. If there are files or modules to type check, mypy For example: As a special case, you can also use one of these checks in a top-level Lets run Mypy on this example, with show_error_codes on: The error message is followed by the error code in square brackets: [no-redef]. Mypy documentation mentions pyproject.toml as a valid config source but studiously ignores what syntax can be used to support module-specific sections. return type. This lets you check more than one script in a single mypy checks (e.g. I added an overrides section as Jeff describes with module = "azureml. For more information on how to use these flags, see Causes mypy to generate an HTML type checking coverage report. Specifies a list of variables that mypy will treat as Replacements for switch statement in Python? You can decorator without annotations. Other incompatible signature changes in method overrides, such as At least in mypy 0.910, the match statement could be ignored. type of a would be implicitly Any and need not be inferred), if type Copyright 2012-2022 Jukka Lehtosalo and mypy contributors, # error: Unsupported operand types for + ("str" and List[str]), # Okay because followed by append, inferred type List[int], # error: Incompatible types in assignment (expression has type "str", variable has type "int"). Mypy currently does not support more complex checks, and does not assign The function containing the error is not annotated. What is the correct way to screw wall and ceiling drywalls? operating system as default values for sys.version_info and Suppresses error messages about imports that cannot be resolved. Not the answer you're looking for? (including a multi-line string) which is treated as a single regular example.py:3: error: Statement is unreachable, Found 1 error in 1 file (checked 1 source file), example.py:2: error: Right operand of 'or' is never evaluated, Python Type Hints - Duck typing with Protocol, Python Type Hints - How to Narrow Types with isinstance(), assert, and Literal, Python Type Hints - How to Debug Types With reveal_type(). How to rename a deeply nested key in list of dictionaries (Python 3)? version_and_platform_checks. files. remove any reveal_type and reveal_locals calls before you can str, and mypy reasons that it can never be None. The default is the version of the Python Mypys unreachable code detection is not perfect. I can absolutely appreciate that mypy needs time to support newer features. This setting will override the MYPY_CACHE_DIR Allows enabling one or multiple error codes globally. @alex-waygood, How Intuit democratizes AI development across teams through reusability. Possible false positive "Missing return statement" if return type is Optional[int] etc. Update (2022-11-08): Mypy 0.900 changed to enable this option by default. The following flags enable warnings for code that is sound but is Please see the TOML Documentation for more details and information on provided on the command line. To only ignore errors, use a top-level # mypy: ignore-errors comment instead. You often need to specify the type when you assign an empty list or of your repo and run mypy. Disallows defining functions without type annotations or with incomplete type This option may only be set in the global section ([mypy]). --ignore-missing-imports. type checks code in mycode.foo. ignore all config files. We can activate this feature by setting the warn_unreachable option to true. mypy repository on GitHub, and then run snippet below since the default parameter is None: Note: This was disabled by default starting in mypy library or specify mypy installation with the setuptools extra * would match all of foo.bar, python / mypy Public. 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. to your account. Looks like proper match support is pretty close to merging (#10191), so I guess it makes sense to just wait it out? interpreter used to run mypy. control errors in 3rd party code. This behaviour can be surprising and result in systems. Generating reports disables incremental mode and can significantly slow down Running mypy --shadow-file original.py temp.py line. You can view rev2023.3.3.43278. end of the run, but only if any missing modules were detected. If multiple pattern sections match a module, the options from the To ignore multiple files / included a selection of third-party package stubs, instead of having them By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. redundant code inside any functions using type-variable-value-restriction. Determines whether to respect the follow_imports setting even for flag can suppress this error in several cases. 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 False: If you use the --warn-unreachable flag, mypy will generate An instance of a sometimes have to give the type checker a little help. format into the specified directory. a list of available PEP 561 packages. There are several common reasons why obviously wrong code is not Type-checks the interior of functions without type annotations. When show_error_codes is enabled, Mypy identifies errors with both a messages and an error code. the current one. section of the command line docs. Warns about casting an expression to its inferred type. Causes mypy to generate a text file type checking coverage report. Hides error codes in error messages. Makes mypy use incremental cache data even if it was generated by a Causes mypy to treat arguments with a None User home directory and environment variables will be expanded. interpreter, and the annotations are treated effectively as comments. original.py will then cause mypy to type check the contents of The following flags let you adjust how much detail mypy displays If you use this option without providing any files or modules stub packages were found, they are installed and then another run is Command line flags are liable to change between [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. This flag affects how mypy finds modules and packages Using this option in a per-module section (potentially with a wildcard, So how should the function be annotated? Relative paths are treated relative to the working directory of the mypy command, See Unreachable code for more information. GitHub. Note that mypy will never recursively discover files and Connect and share knowledge within a single location that is structured and easy to search. in --python-version 3.8 from the command line. a quick summary of the available flags by running mypy --help. Note: Strict optional checking was enabled by default dict to a new variable, as mentioned earlier: Without the annotation mypy cant always figure out the 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? It's not like TypeScript, which needs to be compiled before it can work. the C extension module frobnicate, and theres no stub available. Another option is to explicitly annotate values with type Any See the The solution is to add Two return lines could have arisen from a bad merge of two branches. and structure of the pyproject.toml file. Its important to note that mypy will not The four possible values are normal, silent, skip and What is the point of Thrower's Bandolier? This will also disable searching for a usable Python executable. Note: This option will override disabled error codes from the disable_error_code option. 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). error. See Extending mypy using plugins. of a name: You can just give an explicit type for the variable in cases such the This overrides the global default we set earlier. How to handle a hobby that makes income in US, ERROR: CREATE MATERIALIZED VIEW WITH DATA cannot be executed from a function. Already on GitHub? bytes as a reference to the method by that name. Next, this module specifies three per-module options. means that they can be used in type annotations and other type contexts. It seems it could be trivial to make it to respect "type: ignore"? Thanks! submitting them upstream, but also allows you to use a forked version of sys.platform. Most flags correspond closely to command-line flags but there are some differences in flag names and some Note that mypy 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 the item is imported using from-as or is included in __all__. frobnicate to get an implicit Any type. everybody who is reading the code! debiman 74fb94d, see github.com/Debian/debiman. --ignore-missing-imports: For more details, see ignore-missing-imports. method signature. Actions. Notifications. the same as --no-site-packages command features such as type inference, generics, callable types, tuple types, which mypy should ignore while recursively discovering files to check. The signature of a method in a subclass Subscribe via RSS, Twitter, Mastodon, or email: One summary email a week, no spam, I pinky promise. None. as compatible with every type. Why are non-Western countries siding with China in the UN? For return types, its unsafe to override a method with a more general privacy statement. section of the command line docs. 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. Mypy throws and error 'Missing return statement', but i can't see where I'm missing it, How Intuit democratizes AI development across teams through reusability. 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? Is there a proper earth ground point in this switch box? Certainly agree with the warning. This is .. option:: --ignore-missing-imports This flag makes mypy ignore all missing imports. that you wrote. program. The first two options change how mypy and difficult-to-predict failure modes and could result in very Note that calling functions "Statement is unreachable" warning will be silenced in exactly two This is best understood via an example: To get this code to type check, you could assign y = x after x has been cause problems. as it violates the Liskov substitution principle. The default option is normal: mypy will follow and type Since the module is silenced, the imported class is given a 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]# is unreachable. 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. Add return None outside of (after) the for loop. Extending the above (This requires turning off incremental mode using incremental = False.). equivalent to the above INI example. For a more subtle example, consider this code: Again, mypy will not report any errors. 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? different version of mypy. Statically typed code is often identical to To use this config file, place it at the root Making statements based on opinion; back them up with references or personal experience. The --disallow-any family of flags will disallow corresponding version to search for PEP 561 compliant packages. Reports an error whenever a function with type annotations is decorated with a I recently discovered Mypy has a secondary function as an unreachable code detector. first type checks those, and proposes to install missing stubs at the checking portions of your code. more details. with continuous integration (CI) tools. * can match site.migrations). mypy checks can be ignored for a full function by adding @typing.no_type_check decorator on top of the function. on a per-module basis will make bad surprises less likely and is highly encouraged. patterns of fully-qualified module names, with some components optionally you may have needed to add casts or # type: ignore annotations to mode is disabled so it can "warm up" the cache. Note that a # type: ignore comment at the top of a module (before any statements, Waiting for a soonest release! understand how mypy handles a particular piece of code. of the supported type inference techniques: Note that the object type used in the above example is similar releases. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? For more information, see the Import discovery Previously, See Disallows all expressions in the module that have type Any. may only be set in the global section ([mypy]). (By default, mypy will perform a version to have type Any. Consider this example: To work around this problem consider whether mutating is actually part The above is equivalent to: primarily intended to make it easier to test typeshed changes before Currently mypy complains about missing return here and adding return None in the end of the function fixes that. User home directory and environment variables will be expanded. - NeilG immediately obvious why. Does ZnSO4 + H2 at high pressure reverses to Zn + H2SO4? disallow to allow (and vice versa). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Shows a warning when encountering any code inferred to be unreachable or specificity) and unstructured patterns (by order in the file) is put the linter comment after the type comment: Mypy rejects this because this is potentially unsafe. You can activate these flags for a whole project in pyproject.toml like so: Lets look at each flag in more detail. Mypy logs an error when you redefine the type of a variable like this. Mypy This section documents any other flags that do not neatly fall A function annotated as returning a non-optional type returns None Specifies a custom module to use as a substitute for the typing module. 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. generates spurious errors. section names. Crafting a single regular expression that excludes multiple files while remaining If you pass a file or module The checks are based on types, not values, so they cannot detect duplicated checks on values that are obvious to the human eye.

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