fix: make non-uniform rebinning work for Weight() and friends (#972)

* fix: make non-uniform rebinning work for Weight() and friends

* update changelog

* silence pylint

* fix: use integrated support for adding views

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>

Author: Saransh-cpp

.github/CONTRIBUTING.md

@@ -42,12 +42,12 @@ specific jobs:
 ```console
 $ nox -l # List all the defined sessions
 $ nox -s lint  # Lint only
-$ nox -s tests-3.9  # Python 3.9 tests only
+$ nox -s tests  # Tests only
 $ nox -s docs -- serve  # Build and serve the docs
 $ nox -s make_pickle  # Make a pickle file for this version
 ```
 
-Nox handles everything for you, including setting up an temporary virtual
+Nox handles everything for you, including setting up a temporary virtual
 environment for each run.
 
 ### Pip

docs/changelog.md

@@ -2,6 +2,12 @@
 
 ## Version 1.5
 
+### Version 1.5.1
+
+Make non-uniform rebinning work for Weight() and friends [#972][]
+
+[#972]: https://github.com/scikit-hep/boost-histogram/pull/972
+
 ### Version 1.5.0
 
 #### Features

src/boost_histogram/_internal/hist.py

@@ -921,9 +921,9 @@ def __getitem__(self: H, index: IndexingExpr) -> H | float | Accumulator:
                     for new_j, group in enumerate(groups):
                         for _ in range(group):
                             pos = [slice(None)] * (i)
-                            new_view[(*pos, new_j + 1, ...)] += reduced_view[
-                                (*pos, j, ...)
-                            ]
+                            new_view[(*pos, new_j + 1, ...)] += _to_view(
+                                reduced_view[(*pos, j, ...)]
+                            )
                             j += 1
 
                     reduced = new_reduced

tests/test_storage.py

@@ -301,3 +301,93 @@ def test_empty_axis_histogram(storage):
     )
     assert h2d.sum() == h2d.storage_type.accumulator()
     assert h2d.sum(flow=True) == h2d.storage_type.accumulator()
+
+
+# Issue #971
+def test_non_uniform_rebin_with_weights():
+    # 1D
+    h = bh.Histogram(bh.axis.Regular(20, 1, 5), storage=bh.storage.Weight())
+    h.fill([1.1, 2.2, 3.3, 4.4])
+
+    rslt = np.array(
+        [(1.0, 1.0), (1.0, 1.0), (1.0, 1.0), (0.0, 0.0), (1.0, 1.0)],
+        dtype=[("value", "<f8"), ("variance", "<f8")],
+    )
+
+    hs = h[{0: slice(None, None, bh.rebin(4))}]
+    assert_array_equal(hs.view(), rslt)
+
+    hs = h[{0: bh.rebin(4)}]
+    assert_array_equal(hs.view(), rslt)
+
+    hs = h[{0: bh.rebin(groups=[1, 2, 3, 14])}]
+    assert_array_equal(
+        hs.view(),
+        np.array(
+            [(1.0, 1.0), (0.0, 0.0), (0.0, 0.0), (3.0, 3.0)],
+            dtype=[("value", "<f8"), ("variance", "<f8")],
+        ),
+    )
+    assert_array_equal(hs.axes.edges[0], [1.0, 1.2, 1.6, 2.2, 5.0])
+
+    # nD
+    h = bh.Histogram(
+        bh.axis.Regular(20, 1, 3),
+        bh.axis.Regular(30, 1, 3),
+        bh.axis.Regular(40, 1, 3),
+        storage=bh.storage.Weight(),
+    )
+
+    s = bh.tag.Slicer()
+
+    assert h[{0: s[:: bh.rebin(groups=[1, 2, 17])]}].axes.size == (3, 30, 40)
+    assert h[{1: s[:: bh.rebin(groups=[1, 2, 27])]}].axes.size == (20, 3, 40)
+    assert h[{2: s[:: bh.rebin(groups=[1, 2, 37])]}].axes.size == (20, 30, 3)
+    assert np.all(
+        np.isclose(
+            h[{0: s[:: bh.rebin(groups=[1, 2, 17])]}].axes[0].edges,
+            [1.0, 1.1, 1.3, 3.0],
+        )
+    )
+    assert np.all(
+        np.isclose(
+            h[{1: s[:: bh.rebin(groups=[1, 2, 27])]}].axes[1].edges,
+            [1.0, 1.06666667, 1.2, 3.0],
+        )
+    )
+    assert np.all(
+        np.isclose(
+            h[{2: s[:: bh.rebin(groups=[1, 2, 37])]}].axes[2].edges,
+            [1.0, 1.05, 1.15, 3.0],
+        )
+    )
+
+    assert h[
+        {0: s[:: bh.rebin(groups=[1, 2, 17])], 2: s[:: bh.rebin(groups=[1, 2, 37])]}
+    ].axes.size == (3, 30, 3)
+    assert np.all(
+        np.isclose(
+            h[
+                {
+                    0: s[:: bh.rebin(groups=[1, 2, 17])],
+                    2: s[:: bh.rebin(groups=[1, 2, 37])],
+                }
+            ]
+            .axes[0]
+            .edges,
+            [1.0, 1.1, 1.3, 3],
+        )
+    )
+    assert np.all(
+        np.isclose(
+            h[
+                {
+                    0: s[:: bh.rebin(groups=[1, 2, 17])],
+                    2: s[:: bh.rebin(groups=[1, 2, 37])],
+                }
+            ]
+            .axes[2]
+            .edges,
+            [1.0, 1.05, 1.15, 3.0],
+        )
+    )