From 1969754237c8d6440731467c52aa1fc69258ea35 Mon Sep 17 00:00:00 2001
From: Nathaniel Starkman <nstarman@users.noreply.github.com>
Date: Thu, 18 May 2023 13:36:08 -0400
Subject: [PATCH] Add HasConstantsNamespace

Protocol for the presence of a constants namespace.

Signed-off-by: Nathaniel Starkman <nstarman@users.noreply.github.com>
---
 src/cosmology/api/_core.py      |  3 ++-
 src/cosmology/api/_namespace.py | 17 +++++++++++------
 2 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/src/cosmology/api/_core.py b/src/cosmology/api/_core.py
index 768a7a1..7a58d7b 100644
--- a/src/cosmology/api/_core.py
+++ b/src/cosmology/api/_core.py
@@ -5,6 +5,7 @@
 from typing import TYPE_CHECKING, Protocol, TypeVar, runtime_checkable
 
 from cosmology.api._array_api import Array
+from cosmology.api._namespace import HasConstantsNamespace
 
 if TYPE_CHECKING:
     from cosmology.api._constants import CosmologyConstantsNamespace
@@ -18,7 +19,7 @@
 
 
 @runtime_checkable
-class Cosmology(Protocol[Array, InputT]):  # type: ignore[misc]
+class Cosmology(HasConstantsNamespace, Protocol[Array, InputT]):  # type: ignore[misc]
     """Cosmology API Protocol."""
 
     @property
diff --git a/src/cosmology/api/_namespace.py b/src/cosmology/api/_namespace.py
index f5fad78..47a4d01 100644
--- a/src/cosmology/api/_namespace.py
+++ b/src/cosmology/api/_namespace.py
@@ -19,7 +19,17 @@
 
 
 @runtime_checkable
-class CosmologyNamespace(Protocol):
+class HasConstantsNamespace(Protocol):
+    """Protocol for objects that have a constants module."""
+
+    @property
+    def constants(self) -> CosmologyConstantsNamespace:
+        """The constants namespace for this object."""
+        ...
+
+
+@runtime_checkable
+class CosmologyNamespace(HasConstantsNamespace, Protocol):
     """Runtime-checkable Protocol for the Cosmology API namespace.
 
     Examples
@@ -53,8 +63,3 @@ class CosmologyNamespace(Protocol):
     be a `~cosmology.api.CosmologyConstantsNamespace`, but `isinstance` will not
     check this.
     """
-
-    @property
-    def constants(self) -> CosmologyConstantsNamespace:
-        """The cosmology constants API."""
-        ...