Merge remote-tracking branch 'upstream/master' into map-blocks-schema

* upstream/master: (54 commits)
  Limit repr of arrays containing long strings (pydata#3900)
  expose a few zarr backend functions as semi-public api (pydata#3897)
  Use drawstyle instead of linestyle in plot.step. (pydata#3274)
  Implementation of polyfit and polyval (pydata#3733)
  misplaced quote in whatsnew (pydata#3889)
  Rename ordered_dict_intersection -> compat_dict_intersection (pydata#3887)
  Control attrs of result in `merge()`, `concat()`, `combine_by_coords()` and `combine_nested()` (pydata#3877)
  xfail test_uamiv_format_write (pydata#3885)
  Use `fixes` in PR template (pydata#3886)
  Tweaks to "how_to_release" (pydata#3882)
  whatsnew section for 0.16.0
  Release v0.15.1
  whatsnew for 0.15.1 (pydata#3879)
  update panel documentation (pydata#3880)
  reword the whats-new entry for unit support (pydata#3878)
  Raise error when assigning to IndexVariable.values & IndexVariable.data (pydata#3862)
  Re-enable tests xfailed in pydata#3808 and fix new CFTimeIndex failures due to upstream changes (pydata#3874)
  add spacing in the versions section of the issue report (pydata#3876)
  map_blocks: allow user function to add new unindexed dimension. (pydata#3817)
  Delete associated indexes when deleting coordinate variables. (pydata#3840)
  ...

.github/ISSUE_TEMPLATE/bug_report.md

@@ -25,8 +25,11 @@ assignees: ''
 <!-- this should explain why the current behavior is a problem and why the expected output is a better solution -->
 
 
-#### Output of ``xr.show_versions()``
-<details>
+#### Versions
+
+<details><summary>Output of `xr.show_versions()`</summary>
+
 <!-- Paste the output here xr.show_versions() here -->
 
+
 </details>

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,6 @@
 <!-- Feel free to remove check-list items aren't relevant to your change -->
 
- - [ ] Closes #xxxx
+ - [ ] Fixes #xxxx
  - [ ] Tests added
  - [ ] Passes `isort -rc . && black . && mypy . && flake8`
  - [ ] Fully documented, including `whats-new.rst` for all changes and `api.rst` for new API

HOW_TO_RELEASE.md

@@ -23,7 +23,7 @@ Time required: about an hour.
  4. Check that the ReadTheDocs build is passing.
  5. On the master branch, commit the release in git:
       ```
-      git commit -a -m 'Release v0.X.Y'
+      git commit -am 'Release v0.X.Y'
       ```
  6. Tag the release:
       ```
@@ -60,10 +60,35 @@ Time required: about an hour.
     It's OK to force push to 'stable' if necessary. (We also update the stable 
     branch with `git cherrypick` for documentation only fixes that apply the 
     current released version.)
-12. Add a section for the next release (v.X.(Y+1)) to doc/whats-new.rst.
+12. Add a section for the next release (v.X.Y+1) to doc/whats-new.rst:
+     ```
+     .. _whats-new.0.X.Y+1:
+
+     v0.X.Y+1 (unreleased)
+     ---------------------
+
+     Breaking changes
+     ~~~~~~~~~~~~~~~~
+
+
+     New Features
+     ~~~~~~~~~~~~
+
+
+     Bug fixes
+     ~~~~~~~~~
+
+
+     Documentation
+     ~~~~~~~~~~~~~
+
+
+     Internal Changes
+     ~~~~~~~~~~~~~~~~
+     ```
 13. Commit your changes and push to master again:
       ```
-      git commit -a -m 'New whatsnew section'
+      git commit -am 'New whatsnew section'
       git push upstream master
       ```
     You're done pushing to master!
@@ -88,15 +113,17 @@ Time required: about an hour.
     ```
     git log "$(git tag --sort="v:refname" | sed -n 'x;$p').." --format="%aN" | sort -u
     ```
-    or by replacing `v0.X.Y` with the _previous_ release in:
+    or by substituting the _previous_ release in:
     ```
-    git log v0.X.Y.. --format="%aN" | sort -u
+    git log v0.X.Y-1.. --format="%aN" | sort -u
     ```
+    NB: copying this output into a Google Groups form can cause 
+    [issues](https://groups.google.com/forum/#!topic/xarray/hK158wAviPs) with line breaks, so take care
 
 Note on version numbering:
 
 We follow a rough approximation of semantic version. Only major releases (0.X.0)
-show include breaking changes. Minor releases (0.X.Y) are for bug fixes and
+should include breaking changes. Minor releases (0.X.Y) are for bug fixes and
 backwards compatible new features, but if a sufficient number of new features
 have arrived we will issue a major release even if there are no compatibility
 breaks.

azure-pipelines.yml

@@ -32,15 +32,16 @@ jobs:
   steps:
   - template: ci/azure/unit-tests.yml
 
-- job: MacOSX
-  strategy:
-    matrix:
-      py38:
-        conda_env: py38
-  pool:
-    vmImage: 'macOS-10.13'
-  steps:
-  - template: ci/azure/unit-tests.yml
+# excluded while waiting for https://github.com/conda-forge/libwebp-feedstock/issues/26
+# - job: MacOSX
+#   strategy:
+#     matrix:
+#       py38:
+#         conda_env: py38
+#   pool:
+#     vmImage: 'macOS-10.15'
+#   steps:
+#   - template: ci/azure/unit-tests.yml
 
 - job: Windows
   strategy:

ci/azure/install.yml

@@ -19,7 +19,6 @@ steps:
         --upgrade \
         matplotlib \
         numpy \
-        pandas \
         scipy
     python -m pip install \
         --no-deps \
@@ -30,7 +29,8 @@ steps:
         git+https://github.com/Unidata/cftime \
         git+https://github.com/mapbox/rasterio \
         git+https://github.com/hgrecco/pint \
-        git+https://github.com/pydata/bottleneck
+        git+https://github.com/pydata/bottleneck \
+        git+https://github.com/pandas-dev/pandas
   condition: eq(variables['UPSTREAM_DEV'], 'true')
   displayName: Install upstream dev dependencies
 

ci/requirements/doc.yml

@@ -6,21 +6,22 @@ dependencies:
   - python=3.8
   - bottleneck
   - cartopy
-  - cfgrib
-  - h5netcdf
+  - cfgrib>=0.9
+  - dask>=2.10
+  - h5netcdf>=0.7.4
   - ipykernel
   - ipython
-  - iris
+  - iris>=2.3
   - jupyter_client
   - nbsphinx
-  - netcdf4
+  - netcdf4>=1.5
   - numba
-  - numpy
+  - numpy>=1.17
   - numpydoc
-  - pandas
-  - rasterio
+  - pandas>=1.0
+  - rasterio>=1.1
   - seaborn
   - setuptools
-  - sphinx
-  - sphinx_rtd_theme
-  - zarr
+  - sphinx>=2.3
+  - sphinx_rtd_theme>=0.4
+  - zarr>=2.4

ci/requirements/py36-min-nep18.yml

@@ -11,7 +11,7 @@ dependencies:
   - msgpack-python=0.6  # remove once distributed is bumped. distributed GH3491
   - numpy=1.17
   - pandas=0.25
-  - pint=0.9  # Actually not enough as it doesn't implement __array_function__yet!
+  - pint=0.11
   - pip
   - pytest
   - pytest-cov

conftest.py

@@ -21,3 +21,14 @@ def pytest_runtest_setup(item):
         pytest.skip(
             "set --run-network-tests to run test requiring an " "internet connection"
         )
+
+
+@pytest.fixture(autouse=True)
+def add_standard_imports(doctest_namespace):
+    import numpy as np
+    import pandas as pd
+    import xarray as xr
+
+    doctest_namespace["np"] = np
+    doctest_namespace["pd"] = pd
+    doctest_namespace["xr"] = xr

doc/api-hidden.rst

@@ -379,7 +379,6 @@
    Variable.min
    Variable.no_conflicts
    Variable.notnull
-   Variable.pad_with_fill_value
    Variable.prod
    Variable.quantile
    Variable.rank
@@ -453,7 +452,6 @@
    IndexVariable.min
    IndexVariable.no_conflicts
    IndexVariable.notnull
-   IndexVariable.pad_with_fill_value
    IndexVariable.prod
    IndexVariable.quantile
    IndexVariable.rank

doc/api.rst

@@ -30,6 +30,7 @@ Top-level functions
    zeros_like
    ones_like
    dot
+   polyval
    map_blocks
    show_versions
    set_options
@@ -165,13 +166,15 @@ Computation
    Dataset.groupby_bins
    Dataset.rolling
    Dataset.rolling_exp
+   Dataset.weighted
    Dataset.coarsen
    Dataset.resample
    Dataset.diff
    Dataset.quantile
    Dataset.differentiate
    Dataset.integrate
    Dataset.map_blocks
+   Dataset.polyfit
 
 **Aggregation**:
 :py:attr:`~Dataset.all`
@@ -221,6 +224,7 @@ Reshaping and reorganizing
    Dataset.to_stacked_array
    Dataset.shift
    Dataset.roll
+   Dataset.pad
    Dataset.sortby
    Dataset.broadcast_like
 
@@ -341,6 +345,7 @@ Computation
    DataArray.groupby_bins
    DataArray.rolling
    DataArray.rolling_exp
+   DataArray.weighted
    DataArray.coarsen
    DataArray.dt
    DataArray.resample
@@ -350,6 +355,7 @@ Computation
    DataArray.quantile
    DataArray.differentiate
    DataArray.integrate
+   DataArray.polyfit
    DataArray.str
    DataArray.map_blocks
 
@@ -402,6 +408,7 @@ Reshaping and reorganizing
    DataArray.to_unstacked_dataset
    DataArray.shift
    DataArray.roll
+   DataArray.pad
    DataArray.sortby
    DataArray.broadcast_like
 
@@ -578,6 +585,22 @@ Rolling objects
    core.rolling.DatasetRolling.reduce
    core.rolling_exp.RollingExp
 
+Weighted objects
+================
+
+.. autosummary::
+   :toctree: generated/
+
+   core.weighted.DataArrayWeighted
+   core.weighted.DataArrayWeighted.mean
+   core.weighted.DataArrayWeighted.sum
+   core.weighted.DataArrayWeighted.sum_of_weights
+   core.weighted.DatasetWeighted
+   core.weighted.DatasetWeighted.mean
+   core.weighted.DatasetWeighted.sum
+   core.weighted.DatasetWeighted.sum_of_weights
+
+
 Coarsen objects
 ===============