From 7c8bf4d688788179b07442e8dd1f1a7c173596d6 Mon Sep 17 00:00:00 2001
From: ipeluffo <ipeluffo@gmail.com>
Date: Tue, 14 Apr 2026 11:13:10 +0100
Subject: [PATCH] Refactor `Dependant.is_gen_callable` property for improved
 memory usage

```
Samples: 200000 - current=318.4 MB  peak=318.4 MB
Samples: 100000 - current=159.2 MB  peak=159.2 MB
Samples: 50000 - current=79.6 MB  peak=79.6 MB
Samples: 1000 - current=1.6 MB  peak=1.6 MB
Samples: 500 - current=0.8 MB  peak=0.8 MB
```
---
 fastapi/dependencies/models.py | 63 +++++++++++++++++++++-------------
 1 file changed, 39 insertions(+), 24 deletions(-)

diff --git a/fastapi/dependencies/models.py b/fastapi/dependencies/models.py
index aeda28ac15..c2737df23a 100644
--- a/fastapi/dependencies/models.py
+++ b/fastapi/dependencies/models.py
@@ -56,6 +56,7 @@ class Dependant:
     _is_security_scheme_cache: bool = field(default=None, init=False, repr=False)
     _security_scheme_cache: SecurityBase = field(default=None, init=False, repr=False)
     _security_dependencies_cache: list["Dependant"] = field(default=None, init=False, repr=False)
+    _is_gen_callable_cache: bool = field(default=None, init=False, repr=False)
 
     @property
     def oauth_scopes(self) -> list[str]:
@@ -132,31 +133,45 @@ class Dependant:
 
         return self._security_dependencies_cache
 
-    @cached_property
+    @property
     def is_gen_callable(self) -> bool:
-        if self.call is None:
-            return False  # pragma: no cover
-        if inspect.isgeneratorfunction(
-            _impartial(self.call)
-        ) or inspect.isgeneratorfunction(_unwrapped_call(self.call)):
-            return True
-        if inspect.isclass(_unwrapped_call(self.call)):
-            return False
-        dunder_call = getattr(_impartial(self.call), "__call__", None)  # noqa: B004
-        if dunder_call is None:
-            return False  # pragma: no cover
-        if inspect.isgeneratorfunction(
-            _impartial(dunder_call)
-        ) or inspect.isgeneratorfunction(_unwrapped_call(dunder_call)):
-            return True
-        dunder_unwrapped_call = getattr(_unwrapped_call(self.call), "__call__", None)  # noqa: B004
-        if dunder_unwrapped_call is None:
-            return False  # pragma: no cover
-        if inspect.isgeneratorfunction(
-            _impartial(dunder_unwrapped_call)
-        ) or inspect.isgeneratorfunction(_unwrapped_call(dunder_unwrapped_call)):
-            return True
-        return False
+        if self._is_gen_callable_cache is None:
+            if self.call is None:
+                self._is_gen_callable_cache = False  # pragma: no cover
+            elif inspect.isgeneratorfunction(
+                _impartial(self.call)
+            ) or inspect.isgeneratorfunction(_unwrapped_call(self.call)):
+                self._is_gen_callable_cache = True
+            elif inspect.isclass(_unwrapped_call(self.call)):
+                self._is_gen_callable_cache = False
+
+            # optimization to exit early
+            if self._is_gen_callable_cache is not None:
+                return self._is_gen_callable_cache
+
+            dunder_call = getattr(_impartial(self.call), "__call__", None)  # noqa: B004
+            if dunder_call is None:
+                self._is_gen_callable_cache = False  # pragma: no cover
+            elif inspect.isgeneratorfunction(
+                _impartial(dunder_call)
+            ) or inspect.isgeneratorfunction(_unwrapped_call(dunder_call)):
+                self._is_gen_callable_cache = True
+
+            # optimization to exit early
+            if self._is_gen_callable_cache is not None:
+                return self._is_gen_callable_cache
+
+            dunder_unwrapped_call = getattr(_unwrapped_call(self.call), "__call__", None)  # noqa: B004
+            if dunder_unwrapped_call is None:
+                self._is_gen_callable_cache = False  # pragma: no cover
+            if inspect.isgeneratorfunction(
+                _impartial(dunder_unwrapped_call)
+            ) or inspect.isgeneratorfunction(_unwrapped_call(dunder_unwrapped_call)):
+                self._is_gen_callable_cache = True
+            else:
+                self._is_gen_callable_cache = False
+        
+        return self._is_gen_callable_cache
 
     @cached_property
     def is_async_gen_callable(self) -> bool: