Make base convertors.Convertor generic and annotate its subclasses (#1451)

Co-authored-by: Marcelo Trylesinski <marcelotryle@gmail.com>

diff --git a/starlette/convertors.py b/starlette/convertors.py
index d90a9cd15e507986998a714e751c127e7113366a..e3c03d07c29d9be55fb24781ca6d7e0ff5e045e3 100644 (file)
--- a/starlette/convertors.py
+++ b/starlette/convertors.py
@@ -2,24 +2,26 @@ import math
 import typing
 import uuid
 
+T = typing.TypeVar("T")
 
-class Convertor:
-    regex = ""
 
-    def convert(self, value: str) -> typing.Any:
+class Convertor(typing.Generic[T]):
+    regex: typing.ClassVar[str] = ""
+
+    def convert(self, value: str) -> T:
         raise NotImplementedError()  # pragma: no cover
 
-    def to_string(self, value: typing.Any) -> str:
+    def to_string(self, value: T) -> str:
         raise NotImplementedError()  # pragma: no cover
 
 
 class StringConvertor(Convertor):
     regex = "[^/]+"
 
-    def convert(self, value: str) -> typing.Any:
+    def convert(self, value: str) -> str:
         return value
 
-    def to_string(self, value: typing.Any) -> str:
+    def to_string(self, value: str) -> str:
         value = str(value)
         assert "/" not in value, "May not contain path separators"
         assert value, "Must not be empty"
@@ -29,20 +31,20 @@ class StringConvertor(Convertor):
 class PathConvertor(Convertor):
     regex = ".*"
 
-    def convert(self, value: str) -> typing.Any:
+    def convert(self, value: str) -> str:
         return str(value)
 
-    def to_string(self, value: typing.Any) -> str:
+    def to_string(self, value: str) -> str:
         return str(value)
 
 
 class IntegerConvertor(Convertor):
     regex = "[0-9]+"
 
-    def convert(self, value: str) -> typing.Any:
+    def convert(self, value: str) -> int:
         return int(value)
 
-    def to_string(self, value: typing.Any) -> str:
+    def to_string(self, value: int) -> str:
         value = int(value)
         assert value >= 0, "Negative integers are not supported"
         return str(value)
@@ -51,10 +53,10 @@ class IntegerConvertor(Convertor):
 class FloatConvertor(Convertor):
     regex = "[0-9]+(.[0-9]+)?"
 
-    def convert(self, value: str) -> typing.Any:
+    def convert(self, value: str) -> float:
         return float(value)
 
-    def to_string(self, value: typing.Any) -> str:
+    def to_string(self, value: float) -> str:
         value = float(value)
         assert value >= 0.0, "Negative floats are not supported"
         assert not math.isnan(value), "NaN values are not supported"
@@ -65,10 +67,10 @@ class FloatConvertor(Convertor):
 class UUIDConvertor(Convertor):
     regex = "[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}"
 
-    def convert(self, value: str) -> typing.Any:
+    def convert(self, value: str) -> uuid.UUID:
         return uuid.UUID(value)
 
-    def to_string(self, value: typing.Any) -> str:
+    def to_string(self, value: uuid.UUID) -> str:
         return str(value)