REF: share block methods (#54058)

* REF: share block methods

* Remove unnecessary test

Author: jbrockmendel

pandas/core/internals/blocks.py

@@ -159,10 +159,34 @@ class Block(PandasObject):
 
     __slots__ = ()
     is_numeric = False
-    is_object = False
-    is_extension = False
-    _can_consolidate = True
-    _validate_ndim = True
+
+    @final
+    @cache_readonly
+    def _validate_ndim(self) -> bool:
+        """
+        We validate dimension for blocks that can hold 2D values, which for now
+        means numpy dtypes or DatetimeTZDtype.
+        """
+        dtype = self.dtype
+        return not isinstance(dtype, ExtensionDtype) or isinstance(
+            dtype, DatetimeTZDtype
+        )
+
+    @final
+    @cache_readonly
+    def is_object(self) -> bool:
+        return self.values.dtype == _dtype_obj
+
+    @final
+    @cache_readonly
+    def is_extension(self) -> bool:
+        return not lib.is_np_dtype(self.values.dtype)
+
+    @final
+    @cache_readonly
+    def _can_consolidate(self) -> bool:
+        # We _could_ consolidate for DatetimeTZDtype but don't for now.
+        return not self.is_extension
 
     @final
     @cache_readonly
@@ -1908,10 +1932,6 @@ class ExtensionBlock(libinternals.Block, EABackedBlock):
     ExtensionArrays are limited to 1-D.
     """
 
-    _can_consolidate = False
-    _validate_ndim = False
-    is_extension = True
-
     values: ExtensionArray
 
     def fillna(
@@ -2175,10 +2195,6 @@ def is_numeric(self) -> bool:  # type: ignore[override]
 
         return kind in "fciub"
 
-    @cache_readonly
-    def is_object(self) -> bool:  # type: ignore[override]
-        return self.values.dtype.kind == "O"
-
 
 class NumericBlock(NumpyBlock):
     # this Block type is kept for backwards-compatibility
@@ -2199,12 +2215,6 @@ class NDArrayBackedExtensionBlock(libinternals.NDArrayBackedBlock, EABackedBlock
 
     values: NDArrayBackedExtensionArray
 
-    # error: Signature of "is_extension" incompatible with supertype "Block"
-    @cache_readonly
-    def is_extension(self) -> bool:  # type: ignore[override]
-        # i.e. datetime64tz, PeriodDtype
-        return not isinstance(self.dtype, np.dtype)
-
     @property
     def is_view(self) -> bool:
         """return a boolean if I am possibly a view"""
@@ -2242,9 +2252,6 @@ class DatetimeTZBlock(DatetimeLikeBlock):
     values: DatetimeArray
 
     __slots__ = ()
-    is_extension = True
-    _validate_ndim = True
-    _can_consolidate = False
 
     # Don't use values_for_json from DatetimeLikeBlock since it is
     # an invalid optimization here(drop the tz)