Add exhaustive type checking

Author: ELC

Pipfile

@@ -1,14 +1,17 @@
 [[source]]
+name = "PyPI"
 url = "https://pypi.python.org/simple"
 verify_ssl = true
 
 [dev-packages]
 pytest = "*"
+mypy = "*"
+black = "*"
 
 [packages]
 
 [requires]
-python_version = "3.10"
+python_version = "3.11"
 
 [scripts]
 test = "pytest . -vv"

Pipfile.lock

@@ -1,6 +1,6 @@
 from ..files import SealedFileType, Audio, Text, Image
 
-from typing import TypeVar, Generic
+from typing import TypeVar, Generic, assert_never
 
 T = TypeVar("T", bound=SealedFileType)
 
@@ -13,8 +13,11 @@ def visit(self, element: T) -> None:
         elif isinstance(element, Text):
             PrintText().visit(element)
             return
-
-        PrintImage().visit(element)
+        elif isinstance(element, Image):
+            PrintImage().visit(element)
+            return
+        else:
+            assert_never(element)
 
 
 class PrintAudio(Print[Audio]):

patterns/behavioural/visitor/problem_01/algorithms/print.py

@@ -1,6 +1,6 @@
 from ..files import SealedFileType, Audio, Text, Image
 
-from typing import TypeVar, Generic
+from typing import TypeVar, Generic, assert_never
 
 T = TypeVar("T", bound=SealedFileType)
 
@@ -13,8 +13,11 @@ def visit(self, element: T) -> None:
         elif isinstance(element, Text):
             self.visit_text(element)
             return
-
-        self.visit_image(element)
+        elif isinstance(element, Image):
+            self.visit_image(element)
+            return
+        else:
+            assert_never(element)
 
     def visit_audio(self, element: Audio) -> None:
         print(f"{element.codec=}")

patterns/behavioural/visitor/problem_02/algorithms/print.py

@@ -1,3 +1,4 @@
+from typing import assert_never
 from ..files import SealedFileType, Audio, Text, Image
 
 
@@ -10,6 +11,8 @@ def visit(self, element: SealedFileType) -> None:
                 self.visit_text(text)
             case Image() as image:
                 self.visit_image(image)
+            case _ as unreachable:
+                assert_never(unreachable)
 
     def visit_audio(self, element: Audio) -> None:
         print(f"{element.codec=}")

patterns/behavioural/visitor/solution_08/algorithms/print.py

@@ -1,4 +1,4 @@
-from typing import Generic, TypeVar
+from typing import Generic, TypeVar, assert_never
 from ..files import SealedFileType, Audio, Text, Image
 
 T = TypeVar("T", bound=SealedFileType)
@@ -13,6 +13,8 @@ def visit(self, element: T) -> None:
                 PrintText().visit(text)
             case Image() as image:
                 PrintImage().visit(image)
+            case _ as unreachable:
+                assert_never(unreachable)
 
 
 class PrintAudio(Print[Audio]):

patterns/behavioural/visitor/solution_09/algorithms/print.py

@@ -1,10 +1,10 @@
-from .files import Audio, Image, Text
+from .files import Audio, Image, Text, SealedFileType
 from .algorithms import Print
 
 
 def main():
     collection = [Audio(), Text(), Image()]
-    algorithm = Print()
+    algorithm = Print[SealedFileType]()
     for element in collection:
         algorithm.visit(element)