pull_requests: 1709975387

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1709975387 PR_kwDOAMm_X85l7Cdb 8698 closed 0 New alignment option: `join='strict'` 45271239 Title: New alignment option: `join='strict'` - [ ] Closes #8231 - [x] Closes #6806 - [x] Tests added - [ ] User visible changes (including notable bug fixes) are documented in `whats-new.rst` - [x] What's new entry - [x] Refer to PR ID (cannot be done before the PR has been created) - [x] New functions/methods are listed in `api.rst` - No new functions/methods. ## Motive This PR is motivated by solving of the following issues: - xr.concat concatenates along dimensions that it wasn't asked to #8231 - New alignment option: "exact" without broadcasting OR Turn off automatic broadcasting #6806 **The current PR does not solve the unexpected issue described in #8231 without a change in user-code**. Indeed, in the tests written, it is shown that to get the said expected behavior, the user would have to use the new `join='strict'` mode suggested in #6806 for the concatenation operation. Only in that case, the uniqueness of the indexed dimensions' names will be checked, re-using the same logic that was already applied for `join='override'` in `Aligner.find_matching_indexes` This may not be enough to fix #8231. If that isn't, I can split the PR into two, first one for adding the `join='strict'` for #6806 and later on one for #8321. ## Technical Details I try to detail here my thought process. Please correct me if there is anything wrong. This is my first time digging into this core logic! Here is my understanding of the terms: - An **indexed dimension** is attached to a coordinate variable - An **unindexed dimension** is not attached to a coordinate variable (_"Dimensions without coordinates"_) Input data for Scenario 1, tested in `test_concat_join_coordinate_variables_non_asked_dims` ```python ds1 = Dataset( coords={ "x_center": ("x_center", [1, 2, 3]), "x_outer": ("x_outer", [0.5, 1.5, 2.5, 3.5]), }, ) ds2 = Dataset( coords={ "x_center": ("x_center", [4, 5, 6]), "x_outer": ("x_outer", [4.5, 5.5, 6.5]), }, ) ``` Input data for Scenario 2, tested in `test_concat_join_non_coordinate_variables` ```python ds1 = Dataset( data_vars={ "a": ("x_center", [1, 2, 3]), "b": ("x_outer", [0.5, 1.5, 2.5, 3.5]), }, ) ds2 = Dataset( data_vars={ "a": ("x_center", [4, 5, 6]), "b": ("x_outer", [4.5, 5.5, 6.5]), }, ) ``` Logic for non-indexed dimensions logic was working "as expected", as it relies on `Aligner.assert_unindexed_dim_sizes_equal`, checking that unindexed dimension sizes are equal as its name suggests. (Scenario 1) However, the logic for indexed dimensions was surprising as such an expected check on dimensions' sizes was not performed. A check exists in `Aligner.find_matching_indexes` but was only applied to `join='override'`. Applying it for `join='strict'` too is suggested in this Pull Request. 2024-02-03T17:58:43Z 2024-02-25T09:09:37Z 2024-02-25T09:09:37Z   c095bc726e956aafdfbe35efcacff5dafdda2f89     0 5cc61b08f2a96c71dd497a18d0e48d0228942844 d9760f30662b219182cdc8dedc04dfbe7771942b CONTRIBUTOR   13221727 https://github.com/pydata/xarray/pull/8698  

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