with_prefix can now override

CHANGELOG.md

@@ -4,6 +4,7 @@
 * `envolved` no longer supports python 3.7
 ### Added
 * `FindIterCollectionParser`
+* `with_prefix` can now override many of an env-var's parameters
 ### Fixed
 * `CollectionParser`'s `opener` and `closer` arguments now correctly handle matches that would be split by the delimiter
 * `CollectionParser`'s `closer` argument now correctly handles overlapping matches

docs/envvar.rst

@@ -119,12 +119,14 @@ EnvVars
         .. warning::
             Even if the validator does not mutate the value, it should still return the original value.
 
-    .. method:: with_prefix(prefix: str) -> EnvVar[T]
+    .. method:: with_prefix(prefix: str, *, default = ..., description = ...) -> EnvVar[T]
 
         Return a new EnvVar with the parameters but with a given prefix. This method can be used to re-use an env-var
-        schema to multiple env-vars.
+        schema to multiple env-vars. Can also override additional parameters of the new EnvVar. 
 
         :param prefix: The prefix to use.
+        :param other: If specified, will override the parameters of the new EnvVar. If not specified, the
+         parameters of the original EnvVar will be used. Different subclasses can allow to override additional parameters.
         :return: A new EnvVar with the given prefix, of the same type as the envar being used.
 
     .. method:: patch(value: T | missing | discard) -> typing.ContextManager
@@ -202,6 +204,10 @@ EnvVars
                 users = users_ev.get(reverse=True)  # will return a list of usernames sorted in reverse order
             else:
                 users = users_ev.get()  # will return a list of usernames sorted in ascending order
+    
+    .. method:: with_prefix(prefix: str, *, default = ..., description = ..., type = ..., case_sensitive = ..., strip_whitespaces = ...) -> SingleEnvVar[T]
+
+        See :meth:`Superclass method <EnvVar.with_prefix>`
 
 
 .. class:: SchemaEnvVar
@@ -273,6 +279,10 @@ EnvVars
 
             user_ev.get(age=20, height=168) # will return a User object with the name taken from the environment variables,
             # but with the age and height overridden by the keyword arguments.
+    
+    .. method:: with_prefix(prefix: str, *, default = ..., description = ..., type = ..., on_partial = ...) -> SchemaEnvVar[T]
+
+        See :meth:`Superclass method <EnvVar.with_prefix>`
 
 .. class:: Factory(callback: collections.abc.Callable[[], T])
 

envolved/envvar.py

@@ -65,6 +65,13 @@ class Discard(Enum):
 
 discard = Discard.discard
 
+
+class Unchanged(Enum):
+    unchanged = auto()
+
+
+unchanged = Unchanged.unchanged
+
 Description = Union[str, Sequence[str]]
 
 
@@ -134,7 +141,13 @@ def _get(self, **kwargs: Any) -> T:
         pass
 
     @abstractmethod
-    def with_prefix(self: Self, prefix: str) -> Self:
+    def with_prefix(
+        self: Self,
+        prefix: str,
+        *,
+        default: Union[T, Factory[T], Missing, Discard, Unchanged] = unchanged,
+        description: Union[Description, None, Unchanged] = unchanged,
+    ) -> Self:
         pass
 
     @abstractmethod
@@ -194,15 +207,35 @@ def _get(self, **kwargs: Any) -> T:
             raw_value = raw_value.strip()
         return self.type(raw_value, **kwargs)
 
-    def with_prefix(self, prefix: str) -> SingleEnvVar[T]:
+    def with_prefix(
+        self,
+        prefix: str,
+        *,
+        default: Union[T, Factory[T], Missing, Discard, Unchanged] = unchanged,
+        description: Union[Description, None, Unchanged] = unchanged,
+        type: Union[Type[T], Parser[T], Unchanged] = unchanged,
+        case_sensitive: Union[bool, Unchanged] = unchanged,
+        strip_whitespaces: Union[bool, Unchanged] = unchanged,
+    ) -> SingleEnvVar[T]:
+        if default is unchanged:
+            default = self.default
+        if description is unchanged:
+            description = self.description
+        type_ = type
+        if type_ is unchanged:
+            type_ = self.type
+        if case_sensitive is unchanged:
+            case_sensitive = self.case_sensitive
+        if strip_whitespaces is unchanged:
+            strip_whitespaces = self.strip_whitespaces
         return register_env_var(
             SingleEnvVar(
                 prefix + self._key,
-                self.default,
-                type=self.type,
-                description=self.description,
-                case_sensitive=self.case_sensitive,
-                strip_whitespaces=self.strip_whitespaces,
+                default,
+                type=type_,
+                description=description,
+                case_sensitive=case_sensitive,
+                strip_whitespaces=strip_whitespaces,
                 validators=self._validators,
             )
         )
@@ -292,14 +325,31 @@ def _get(self, **kwargs: Any) -> T:
             raise errs[0]
         return self._type(*pos_values, **kw_values)
 
-    def with_prefix(self, prefix: str) -> SchemaEnvVar[T]:
+    def with_prefix(
+        self,
+        prefix: str,
+        *,
+        default: Union[T, Factory[T], Missing, Discard, Unchanged] = unchanged,
+        description: Union[Unchanged, None, Description] = unchanged,
+        type: Union[Type[T], Parser[T], Unchanged] = unchanged,
+        on_partial: Union[T, Missing, AsDefault, Discard, Factory[T], Unchanged] = unchanged,
+    ) -> SchemaEnvVar[T]:
+        if default is unchanged:
+            default = self.default
+        if description is unchanged:
+            description = self.description
+        type_ = type
+        if type_ is unchanged:
+            type_ = self.type
+        if on_partial is unchanged:
+            on_partial = self.on_partial
         return register_env_var(
             SchemaEnvVar(
                 {k: v.with_prefix(prefix) for k, v in self._args.items()},
-                self.default,
-                type=self._type,
-                description=self.description,
-                on_partial=self.on_partial,
+                default,
+                type=type_,
+                description=description,
+                on_partial=on_partial,
                 validators=self._validators,
                 pos_args=tuple(v.with_prefix(prefix) for v in self._pos_args),
             )

tests/unittests/test_single_var.py

@@ -158,6 +158,24 @@ def test_override_default(monkeypatch):
     assert a1.get() == 1
 
 
+def test_override_default_in_constr(monkeypatch):
+    parent = env_var("a", type=int)
+
+    a0 = parent.with_prefix("0")
+    a1 = parent.with_prefix("1", default=1)
+    monkeypatch.setenv("0a", "0")
+    assert a0.get() == 0
+    assert a1.get() == 1
+
+
+def test_override_type(monkeypatch):
+    parent = env_var("a", type=int)
+
+    a1 = parent.with_prefix("1", default=1, type=len)
+    assert a1.default == 1
+    assert a1.type == len
+
+
 def test_patch():
     a = env_var("a", type=int)
     with a.patch(-1):