add dataclass_nested_eq decorator (#378)

* add `dataclass_nested_eq` decorator

* decorate SpatialData with `dataclass_nested_eq`

* update CHANGELOG.md

* docstring

* formatting

CHANGELOG.md

@@ -12,6 +12,8 @@
 - added `WeldxFile` wrapper to handle asdf files with history and schemas more
   easily. [[#341]](https://github.com/BAMWelDX/weldx/pull/341).
 - add `"step"` as additional method to `util.xr_interp_like` [[#363]](https://github.com/BAMWelDX/weldx/pull/363)
+- add `util.compare_nested_eq` decorator for dataclasses with array-like
+  fields [[#378]](https://github.com/BAMWelDX/weldx/pull/378)
 
 ### changes
 

weldx/geometry.py

@@ -2294,6 +2294,7 @@ def spatial_data(
 # SpatialData --------------------------------------------------------------------------
 
 
+@ut.dataclass_nested_eq
 @dataclass
 class SpatialData:
     """Represent 3D point cloud data with optional triangulation.

weldx/util.py

@@ -128,6 +128,48 @@ def inner_decorator(
     return inner_decorator
 
 
+def dataclass_nested_eq(original_class):
+    """Set class :code:`__eq__` using :code:`util.compare_nested` on :code:`__dict__`.
+
+    Useful for implementing :code:`__eq__` on classes
+    created with :code:`@dataclass` decorator.
+
+    Parameters
+    ----------
+    original_class:
+        original class to decorate
+
+    Returns
+    -------
+    type
+        The class with overridden :code:`__eq__` function.
+
+    Examples
+    --------
+    A simple dataclass could look like this::
+
+        @dataclass_nested_eq
+        @dataclass
+        class A:
+            a: np.ndarray
+
+        a = A(np.arange(3))
+        b = A(np.arange(3))
+        assert a==b
+
+    """
+
+    def new_eq(self, other):
+        if not isinstance(other, type(self)):
+            return False
+
+        return compare_nested(self.__dict__, other.__dict__)
+
+    # set new eq function
+    original_class.__eq__ = new_eq  # Set the class' __eq__ to the new one
+    return original_class
+
+
 def _clean_notebook(file: Union[str, Path]):  # pragma: no cover
     """Clean ID metadata, output and execution count from jupyter notebook cells.