BUG: preserve EA in pd.array (#48889)

* BUG: preserve EA in pd.array

* fix 32bit builds

Author: jbrockmendel

pandas/core/construction.py

@@ -49,6 +49,7 @@
 )
 from pandas.core.dtypes.common import (
     is_datetime64_ns_dtype,
+    is_dtype_equal,
     is_extension_array_dtype,
     is_float_dtype,
     is_integer_dtype,
@@ -328,6 +329,14 @@ def array(
     if isinstance(dtype, str):
         dtype = registry.find(dtype) or dtype
 
+    if isinstance(data, ExtensionArray) and (
+        dtype is None or is_dtype_equal(dtype, data.dtype)
+    ):
+        # e.g. TimedeltaArray[s], avoid casting to PandasArray
+        if copy:
+            return data.copy()
+        return data
+
     if is_extension_array_dtype(dtype):
         cls = cast(ExtensionDtype, dtype).construct_array_type()
         return cls._from_sequence(data, dtype=dtype, copy=copy)

pandas/tests/arrays/test_array.py

@@ -124,6 +124,26 @@
             None,
             TimedeltaArray._from_sequence(["1H", "2H"]),
         ),
+        (
+            # preserve non-nano, i.e. don't cast to PandasArray
+            TimedeltaArray._simple_new(
+                np.arange(5, dtype=np.int64).view("m8[s]"), dtype=np.dtype("m8[s]")
+            ),
+            None,
+            TimedeltaArray._simple_new(
+                np.arange(5, dtype=np.int64).view("m8[s]"), dtype=np.dtype("m8[s]")
+            ),
+        ),
+        (
+            # preserve non-nano, i.e. don't cast to PandasArray
+            TimedeltaArray._simple_new(
+                np.arange(5, dtype=np.int64).view("m8[s]"), dtype=np.dtype("m8[s]")
+            ),
+            np.dtype("m8[s]"),
+            TimedeltaArray._simple_new(
+                np.arange(5, dtype=np.int64).view("m8[s]"), dtype=np.dtype("m8[s]")
+            ),
+        ),
         # Category
         (["a", "b"], "category", pd.Categorical(["a", "b"])),
         (