use _repr_inline_ for indexes that define it (#7183)

* use the inline repr, if available

* remove the unused max_width argument

* also remove the unused is_index parameter

* add tests for the index summarizer

* add a basic _repr_inline_ implementation

* don't delegate to __repr__ since _repr_inline_ is now guaranteed to exist

* update the test to check the default implementation

* don't strip the `Index` suffix

* undo the code simplification: pandas indexes use the same code path

and the raw pandas indexes don't define `_repr_inline_`.

* move the inline index repr formatting to a separate function

* properly use the max_width setting

* fix the definition of the `_repr_inline_` method

* disable `mypy` for the index formatting test

It does not allow reassigning the method, and it also complains about
an attribute created in the constructor.

* styling [skip-ci]

* trigger CI

* add a comment explaining why we need the `repr` fallback

Author: keewis

xarray/core/formatting.py

@@ -408,10 +408,26 @@ def coords_repr(coords, col_width=None, max_rows=None):
     )
 
 
-def summarize_index(
-    name: Hashable, index, col_width: int, max_width: int = None, is_index: bool = False
-):
-    return pretty_print(f"    {name} ", col_width) + f"{repr(index)}"
+def inline_index_repr(index, max_width=None):
+    if hasattr(index, "_repr_inline_"):
+        repr_ = index._repr_inline_(max_width=max_width)
+    else:
+        # fallback for the `pandas.Index` subclasses from
+        # `Indexes.get_pandas_indexes` / `xr_obj.indexes`
+        repr_ = repr(index)
+
+    return repr_
+
+
+def summarize_index(name: Hashable, index, col_width: int, max_width: int = None):
+    if max_width is None:
+        max_width = OPTIONS["display_width"]
+
+    preformatted = pretty_print(f"    {name} ", col_width)
+
+    index_width = max_width - len(preformatted)
+    repr_ = inline_index_repr(index, max_width=index_width)
+    return preformatted + repr_
 
 
 def nondefault_indexes(indexes):

xarray/core/indexes.py

@@ -133,6 +133,9 @@ def _copy(self, deep: bool = True, memo: dict[int, Any] | None = None) -> Index:
     def __getitem__(self, indexer: Any):
         raise NotImplementedError()
 
+    def _repr_inline_(self, max_width):
+        return self.__class__.__name__
+
 
 def _maybe_cast_to_cftimeindex(index: pd.Index) -> pd.Index:
     from ..coding.cftimeindex import CFTimeIndex

xarray/tests/test_formatting.py

@@ -219,6 +219,31 @@ def test_attribute_repr(self) -> None:
         assert "\n" not in newlines
         assert "\t" not in tabs
 
+    def test_index_repr(self):
+        from xarray.core.indexes import Index
+
+        class CustomIndex(Index):
+            def __init__(self, names):
+                self.names = names
+
+            def __repr__(self):
+                return f"CustomIndex(coords={self.names})"
+
+        coord_names = ["x", "y"]
+        index = CustomIndex(coord_names)
+        name = "x"
+
+        normal = formatting.summarize_index(name, index, col_width=20)
+        assert name in normal
+        assert "CustomIndex" in normal
+
+        CustomIndex._repr_inline_ = (
+            lambda self, max_width: f"CustomIndex[{', '.join(self.names)}]"
+        )
+        inline = formatting.summarize_index(name, index, col_width=20)
+        assert name in inline
+        assert index._repr_inline_(max_width=40) in inline
+
     def test_diff_array_repr(self) -> None:
         da_a = xr.DataArray(
             np.array([[1, 2, 3], [4, 5, 6]], dtype="int64"),