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docs: add note about directly checking overlays with mypy

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Dima Gerasimov 2023-12-20 18:07:34 +00:00 • committed by karlicoss
parent 84d835962d
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doc/OVERLAYS.org
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@ -32,7 +32,7 @@ Consider a toy package/module structure with minimal code, wihout any actual dat
# TODO mention resolution? reorder_editable
* Installing
* Installing (editable install)
NOTE: this was tested with =python 3.10= and =pip 23.3.2=.
@ -62,7 +62,7 @@ Verify the setup:
This basically means that modules will be searched in both paths, with overlay taking precedence.
* Testing
* Testing (editable install)
: $ python3 -c 'import my.reddit as R; print(R.upvotes())'
: [main] my.reddit hello
@ -84,7 +84,7 @@ As you can see it's merged data from =gdpr= (from =main= package) and =talon= (f
So far so good, let's see how it works with mypy.
* Mypy support
* Mypy support (editable install)
To check that mypy works as expected I injected some statements in modules that have no impact on runtime,
but should trigger mypy, like this =trigger_mypy_error: str = 123=:
@ -118,7 +118,7 @@ So everything else is ignored?
It even seems to have a test for a similar usecase, which is quite sad.
https://github.com/python/mypy/blob/1dd8e7fe654991b01bd80ef7f1f675d9e3910c3a/mypy/test/testmodulefinder.py#L64-L71
TODO For now I'm going to open an issue in mypy repository and ask why is that the case.
For now, I opened an issue in mypy repository https://github.com/python/mypy/issues/16683
But ok, maybe mypy treats =main= as an external package somhow but still type checks it properly?
Let's see what's going on with imports:
@ -142,3 +142,39 @@ Let's see what's going on with imports:
: Found 4 errors in 2 files (checked 4 source files)
Nope -- looks like it's completely unawareof =main=, and what's worst, by default (without tweaking =--follow-imports=), these errors would be suppressed.
* What if we don't install at all?
Instead of editable install let's try running mypy directly over source files
First let's only check =main= package:
: $ MYPYPATH=main/src mypy --namespace-packages --strict -p my
: main/src/my/twitter/gdpr.py:9: error: Incompatible types in assignment (expression has type "int", variable has type "str") [assignment]
: trigger_mypy_error: str = 123
: ^~~
: main/src/my/reddit.py:11: error: Incompatible types in assignment (expression has type "int", variable has type "str") [assignment]
: trigger_mypy_error: str = 123
: ^~~
: Found 2 errors in 2 files (checked 6 source files)
As expected, it found both errors.
Now with overlay as well:
: $ MYPYPATH=overlay/src:main/src mypy --namespace-packages --strict -p my
: overlay/src/my/twitter/all.py:6: note: In module imported here:
: main/src/my/twitter/gdpr.py:9: error: Incompatible types in assignment (expression has type "int", variable has type "str") [assignment]
: trigger_mypy_error: str = 123
: ^~~
: overlay/src/my/twitter/talon.py:9: error: Incompatible types in assignment (expression has type "int", variable has type "str")
: [assignment]
: trigger_mypy_error: str = 123
: ^~~
: Found 2 errors in 2 files (checked 4 source files)
Interesting enough, this is slightly better than the editable install (it detected error in =gdpr.py= as well).
But still no =reddit.py= error.
TODO possibly worth submitting to mypy issue tracker as well...
Overall it seems that properly type checking modules in overlays (especially the ones actually overriding/extending base modules) is kinda problematic.