ensure_type: cache the type adaptors

for a much more efficient type checking of complex types (using pydantic) at runtime:

before:

  124 μs ± 82.5 ns per loop (mean ± std. dev. of 7 runs, 10,000 loops each)

after:

  1.81 μs ± 4.74 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

for comparison, when using isinstance:

  629 ns ± 9.26 ns per loop (mean ± std. dev. of 7 runs, 1,000,000 loops each)

Signed-off-by: Gaëtan Lehmann <[email protected]>

Author: glehmann

lib/common.py

@@ -72,6 +72,8 @@ def expand_scope_relative_nodeid(scoped_nodeid, scope, ref_nodeid):
 def callable_marker(value, request):
 T = TypeVar("T")
 
+_ensure_type_cache: Dict[type, TypeAdapter] = {}
+
 def ensure_type(typ: Type[T], value: Any) -> T:
     """
     Converts a value to the specified type.
@@ -85,7 +87,11 @@ def ensure_type(typ: Type[T], value: Any) -> T:
     except TypeError:
         # not just a simple type, lets try with pydantic
         with suppress(ValidationError):
-            TypeAdapter(typ).validate_python(value)
+            if typ in _ensure_type_cache:
+                ta = _ensure_type_cache[typ]
+            else:
+                ta = _ensure_type_cache.setdefault(typ, TypeAdapter(typ))
+            ta.validate_python(value)
             ok = True
     if not ok:
         raise TypeError(f"'{type(value).__name__}' object is not of the expected type '{typ.__name__}'")