Complete typing with strict type-checking #43

Avasam · 2024-08-25T03:22:30Z

Closes #42
I figured this library is small enough I could lend a hand.

This is everything to have complete type annotations, be on par with typeshed's stubs, and use strict type-checking. I can split into smaller PRs if needed.

More details in GitHub file comments.

Avasam · 2024-08-25T03:24:16Z

.github/workflows/tests.yaml

@@ -18,7 +18,7 @@ jobs:
      - name: run the tests
        run: python3 tests.py 
      - name: verify type hints
-        run: mypy datemath
+        run: mypy . --strict


Running on tests is important too. This ensures expected usage is correctly typed. In fact, it found that parse was missing the int annotation on its first parameter.

Avasam · 2024-08-25T03:24:53Z

datemath/__init__.py

@@ -1,9 +1,18 @@
-from .helpers import parse, DateMathException
+from __future__ import annotations


This allows the use of | in Pyton < 3.10, and use symbols that won't be present at runtime, in annotations.

Avasam · 2024-08-25T03:25:53Z

datemath/__init__.py

+    from typing_extensions import Unpack
+    from arrow import Arrow
+
+from .helpers import ParseParams, parse as parse, DateMathException as DateMathException


as imports without renaming is a typing convention understood by type-checkers to mean that the symbol is purposefully / explicitly re-exported (the other option is to use __all__)

Avasam · 2024-08-25T03:27:27Z

datemath/__init__.py

+
+from .helpers import ParseParams, parse as parse, DateMathException as DateMathException
+
+def dm(expr: str | int, **kwargs: Unpack[ParseParams]) -> Arrow:


By using an unpacked TypedDict to annotate kwargs, you don't have to duplicate all your default keyword argument parameter's default values to have these functions fully typed.

Avasam · 2024-08-25T03:27:39Z

datemath/helpers.py

@@ -78,7 +77,13 @@ def unitMap(c: str) -> str:
    else:
        raise DateMathException("Not a valid timeunit: {0}".format(c))

-def parse(expression: str, now: Any = None, tz: str = 'UTC', type: Any = None, roundDown: bool = True) -> Arrow:
+class ParseParams(TypedDict, total=False):


See comment in datemath/__init__.py
total=False means all members are optional (since we use this to annotate optional kwargs)

Avasam · 2024-08-25T03:29:50Z

datemath/helpers.py

    if expression == 'now':
        if debug: print("parse() - Now, no dm: {0}".format(now))
        if type:
-            return getattr(now, type)
+            return cast(Arrow, getattr(now, type))


In strict mode, mypy will whine about returning Any from a typed function.
This can either be cast or type-ignored to accept the "type unsafety".

Suggested change

return cast(Arrow, getattr(now, type))

return getattr(now, type) # type: ignore[no-any-return]

Avasam · 2024-08-25T03:30:41Z

datemath/helpers.py

@@ -101,15 +106,16 @@ def parse(expression: str, now: Any = None, tz: str = 'UTC', type: Any = None, r
        if debug: print("parse() - will now convert tz to {0}".format(tz))
        now = now.to(tz)

+    expression = str(expression)


Less runtime casting in some cases. But more importantly, this is now type-safe.

Avasam · 2024-08-25T03:32:30Z

datemath/helpers.py

+        now = now.floor(unit)  # type: ignore[arg-type]
    else:
-        now = now.ceil(unit)
+        now = now.ceil(unit) # type: ignore[arg-type]


arrow types these only with the literal strings they accept. I figured you'd probably prefer keeping the types and checks simpler with a more general str, as any usage of roundDate would also have to comply to only using statically known literals.

Avasam · 2024-08-25T03:33:06Z

tests-legacy.py

@@ -1,4 +1,4 @@
-import unittest2 as unittest


unittest2 is untyped, but also no longer needed without Python 2 support.

This file is going to get removed in the next release anyways since this package is only going to be python3 going forward

Avasam · 2024-08-25T03:46:11Z

datemath/helpers.py

@@ -142,7 +148,7 @@ def parse(expression: str, now: Any = None, tz: str = 'UTC', type: Any = None, r
    rettime = evaluate(math, time, tz, roundDown)

    if type:
-        return getattr(rettime, type)
+        return cast(Arrow, getattr(rettime, type))


In strict mode, mypy will whine about returning Any from a typed function.
This can either be cast or type-ignored to accept the "type unsafety".

Suggested change

return cast(Arrow, getattr(rettime, type))

return getattr(rettime, type) # type: ignore[no-any-return]

nickmaccarthy · 2024-08-26T17:58:09Z

Thank you so much for your contribution @Avasam ! This is quite awesome!! I've been writing so much golang lately that I have taking the typing for granted and it seems folks really needed it for this module. I'll approve it and merge it. I'll get a release out soon. There are few other things I'd like to tidy up before the next one first related to the legacy python 2.7 support we had.

Avasam · 2024-08-26T21:50:41Z

requirements-3.txt

@@ -9,8 +9,7 @@ docutils==0.15.2
 freezegun==1.2.2
 idna==2.7
 linecache2==1.0.0
-mypy==1.5.1
-mypy-extensions==1.0.0
+mypy==1.7.1


I'd personally bump mypy all the way to latest. 1.7 is the minimum where Unpack is no longer an incomplete feature https://mypy-lang.blogspot.com/2023/11/mypy-17-released.html

Thank you for this. mypy is only used in this package to do the type checking so its probably good that its at the latest anyways. That got the tests to pass now

Avasam commented Aug 25, 2024

View reviewed changes

Avasam force-pushed the complete-typing-with-strict-checking branch 2 times, most recently from 2fa344b to c90f0bc Compare August 25, 2024 03:41

Avasam commented Aug 25, 2024

View reviewed changes

Avasam force-pushed the complete-typing-with-strict-checking branch from c90f0bc to 5d1bb8f Compare August 25, 2024 03:49

Complete typing with strict type-checking

360cc11

Avasam force-pushed the complete-typing-with-strict-checking branch from 5d1bb8f to 360cc11 Compare August 26, 2024 21:46

Avasam commented Aug 26, 2024

View reviewed changes

nickmaccarthy merged commit c4c6265 into nickmaccarthy:master Aug 27, 2024
1 check passed

Avasam deleted the complete-typing-with-strict-checking branch August 27, 2024 14:13

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Complete typing with strict type-checking #43

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		@@ -1,9 +1,18 @@
		from .helpers import parse, DateMathException
		from __future__ import annotations


		from .helpers import ParseParams, parse as parse, DateMathException as DateMathException

		def dm(expr: str \| int, **kwargs: Unpack[ParseParams]) -> Arrow:

	return cast(Arrow, getattr(now, type))
	return getattr(now, type) # type: ignore[no-any-return]

	return cast(Arrow, getattr(rettime, type))
	return getattr(rettime, type) # type: ignore[no-any-return]

Complete typing with strict type-checking #43

Complete typing with strict type-checking #43

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