Merge remote-tracking branch 'upstream/master' into read_grid_mapping…

…_and_bounds_as_coords

* upstream/master: (51 commits)
  Ensure maximum accuracy when encoding and decoding cftime.datetime values (pydata#4758)
  Fix `bounds_error=True` ignored with 1D interpolation (pydata#4855)
  add a drop_conflicts strategy for merging attrs (pydata#4827)
  update pre-commit hooks (mypy) (pydata#4883)
  ensure warnings cannot become errors in assert_ (pydata#4864)
  update pre-commit hooks (pydata#4874)
  small fixes for the docstrings of swap_dims and integrate (pydata#4867)
  Modify _encode_datetime_with_cftime for compatibility with cftime > 1.4.0 (pydata#4871)
  vélin (pydata#4872)
  don't skip the doctests CI (pydata#4869)
  fix da.pad example for numpy 1.20 (pydata#4865)
  temporarily pin dask (pydata#4873)
  Add units if "unit" is in the attrs. (pydata#4850)
  speed up the repr for big MultiIndex objects (pydata#4846)
  dim -> coord in DataArray.integrate (pydata#3993)
  WIP: backend interface, now it uses subclassing  (pydata#4836)
  weighted: small improvements (pydata#4818)
  Update related-projects.rst (pydata#4844)
  iris update doc url (pydata#4845)
  Faster unstacking (pydata#4746)
  ...

.github/ISSUE_TEMPLATE/config.yml

@@ -4,7 +4,5 @@ contact_links:
     url: https://github.com/pydata/xarray/discussions
     about: |
       Ask questions and discuss with other community members here.
-      If you have a question like "How do I concatenate a list of datasets?" then 
+      If you have a question like "How do I concatenate a list of datasets?" then
       please include a self-contained reproducible example if possible.
-
-   

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,6 +2,6 @@
 
 - [ ] Closes #xxxx
 - [ ] Tests added
-- [ ] Passes `isort . && black . && mypy . && flake8`
+- [ ] Passes `pre-commit run --all-files`
 - [ ] User visible changes (including notable bug fixes) are documented in `whats-new.rst`
 - [ ] New functions/methods are listed in `api.rst`

.github/actions/detect-ci-trigger/action.yaml

@@ -0,0 +1,29 @@
+name: Detect CI Trigger
+description: |
+  Detect a keyword used to control the CI in the subject line of a commit message.
+inputs:
+  keyword:
+    description: |
+      The keyword to detect.
+    required: true
+outputs:
+  trigger-found:
+    description: |
+      true if the keyword has been found in the subject line of the commit message
+    value: ${{ steps.detect-trigger.outputs.CI_TRIGGERED }}
+runs:
+  using: "composite"
+  steps:
+    - name: detect trigger
+      id: detect-trigger
+      run: |
+        bash $GITHUB_ACTION_PATH/script.sh ${{ github.event_name }} ${{ inputs.keyword }}
+      shell: bash
+    - name: show detection result
+      run: |
+        echo "::group::final summary"
+        echo "commit message: ${{ steps.detect-trigger.outputs.COMMIT_MESSAGE }}"
+        echo "trigger keyword: ${{ inputs.keyword }}"
+        echo "trigger found: ${{ steps.detect-trigger.outputs.CI_TRIGGERED }}"
+        echo "::endgroup::"
+      shell: bash

.github/actions/detect-ci-trigger/script.sh

@@ -0,0 +1,47 @@
+#!/usr/bin/env bash
+event_name="$1"
+keyword="$2"
+
+echo "::group::fetch a sufficient number of commits"
+echo "skipped"
+# git log -n 5 2>&1
+# if [[ "$event_name" == "pull_request" ]]; then
+#     ref=$(git log -1 --format='%H')
+#     git -c protocol.version=2 fetch --deepen=2 --no-tags --prune --progress -q origin $ref 2>&1
+#     git log FETCH_HEAD
+#     git checkout FETCH_HEAD
+# else
+#     echo "nothing to do."
+# fi
+# git log -n 5 2>&1
+echo "::endgroup::"
+
+echo "::group::extracting the commit message"
+echo "event name: $event_name"
+if [[ "$event_name" == "pull_request" ]]; then
+    ref="HEAD^2"
+else
+    ref="HEAD"
+fi
+
+commit_message="$(git log -n 1 --pretty=format:%s "$ref")"
+
+if [[ $(echo $commit_message | wc -l) -le 1 ]]; then
+    echo "commit message: '$commit_message'"
+else
+    echo -e "commit message:\n--- start ---\n$commit_message\n--- end ---"
+fi
+echo "::endgroup::"
+
+echo "::group::scanning for the keyword"
+echo "searching for: '$keyword'"
+if echo "$commit_message" | grep -qF "$keyword"; then
+    result="true"
+else
+    result="false"
+fi
+echo "keyword detected: $result"
+echo "::endgroup::"
+
+echo "::set-output name=COMMIT_MESSAGE::$commit_message"
+echo "::set-output name=CI_TRIGGERED::$result"

.github/stale.yml

@@ -56,4 +56,4 @@ limitPerRun: 1  # start with a small number
 
 # issues:
 #   exemptLabels:
-#     - confirmed
+#     - confirmed

.github/workflows/ci-additional.yaml

@@ -0,0 +1,189 @@
+name: CI Additional
+on:
+  push:
+    branches:
+      - "*"
+  pull_request:
+    branches:
+      - "*"
+  workflow_dispatch: # allows you to trigger manually
+
+jobs:
+  detect-ci-trigger:
+    name: detect ci trigger
+    runs-on: ubuntu-latest
+    if: github.event_name == 'push' || github.event_name == 'pull_request'
+    outputs:
+      triggered: ${{ steps.detect-trigger.outputs.trigger-found }}
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 2
+      - uses: ./.github/actions/detect-ci-trigger
+        id: detect-trigger
+        with:
+          keyword: "[skip-ci]"
+
+  test:
+    name: ${{ matrix.os }} ${{ matrix.env }}
+    runs-on: ${{ matrix.os }}
+    needs: detect-ci-trigger
+    if: needs.detect-ci-trigger.outputs.triggered == 'false'
+    defaults:
+      run:
+        shell: bash -l {0}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ["ubuntu-latest"]
+        env:
+          [
+            "py37-bare-minimum",
+            "py37-min-all-deps",
+            "py37-min-nep18",
+            "py38-all-but-dask",
+            "py38-backend-api-v2",
+            "py38-flaky",
+          ]
+    steps:
+      - name: Cancel previous runs
+        uses: styfle/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ github.token }}
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0 # Fetch all history for all branches and tags.
+
+      - name: Set environment variables
+        run: |
+          if [[ ${{ matrix.env }} == "py38-backend-api-v2" ]] ;
+          then
+            echo "CONDA_ENV_FILE=ci/requirements/environment.yml" >> $GITHUB_ENV
+            echo "XARRAY_BACKEND_API=v2" >> $GITHUB_ENV
+
+          elif [[ ${{ matrix.env }} == "py38-flaky" ]] ;
+          then
+            echo "CONDA_ENV_FILE=ci/requirements/environment.yml" >> $GITHUB_ENV
+            echo "PYTEST_EXTRA_FLAGS=--run-flaky --run-network-tests" >> $GITHUB_ENV
+
+          else
+            echo "CONDA_ENV_FILE=ci/requirements/${{ matrix.env }}.yml" >> $GITHUB_ENV
+          fi
+      - name: Cache conda
+        uses: actions/cache@v2
+        with:
+          path: ~/conda_pkgs_dir
+          key:
+            ${{ runner.os }}-conda-${{ matrix.env }}-${{
+            hashFiles('ci/requirements/**.yml') }}
+
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          channels: conda-forge
+          channel-priority: strict
+          mamba-version: "*"
+          activate-environment: xarray-tests
+          auto-update-conda: false
+          python-version: 3.8
+          use-only-tar-bz2: true
+
+      - name: Install conda dependencies
+        run: |
+          mamba env update -f $CONDA_ENV_FILE
+
+      - name: Install xarray
+        run: |
+          python -m pip install --no-deps -e .
+
+      - name: Version info
+        run: |
+          conda info -a
+          conda list
+          python xarray/util/print_versions.py
+      - name: Import xarray
+        run: |
+          python -c "import xarray"
+      - name: Run tests
+        run: |
+          python -m pytest -n 4 \
+             --cov=xarray \
+             --cov-report=xml \
+             $PYTEST_EXTRA_FLAGS
+
+      - name: Upload code coverage to Codecov
+        uses: codecov/codecov-action@v1
+        with:
+          file: ./coverage.xml
+          flags: unittests,${{ matrix.env }}
+          env_vars: RUNNER_OS
+          name: codecov-umbrella
+          fail_ci_if_error: false
+  doctest:
+    name: Doctests
+    runs-on: "ubuntu-latest"
+    defaults:
+      run:
+        shell: bash -l {0}
+
+    steps:
+      - name: Cancel previous runs
+        uses: styfle/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ github.token }}
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0 # Fetch all history for all branches and tags.
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          channels: conda-forge
+          channel-priority: strict
+          mamba-version: "*"
+          activate-environment: xarray-tests
+          auto-update-conda: false
+          python-version: "3.8"
+
+      - name: Install conda dependencies
+        run: |
+          mamba env update -f ci/requirements/environment.yml
+      - name: Install xarray
+        run: |
+          python -m pip install --no-deps -e .
+      - name: Version info
+        run: |
+          conda info -a
+          conda list
+          python xarray/util/print_versions.py
+      - name: Run doctests
+        run: |
+          python -m pytest --doctest-modules xarray --ignore xarray/tests
+
+  min-version-policy:
+    name: Minimum Version Policy
+    runs-on: "ubuntu-latest"
+    needs: detect-ci-trigger
+    if: needs.detect-ci-trigger.outputs.triggered == 'false'
+    defaults:
+      run:
+        shell: bash -l {0}
+
+    steps:
+      - name: Cancel previous runs
+        uses: styfle/cancel-workflow-action@0.6.0
+        with:
+          access_token: ${{ github.token }}
+      - uses: actions/checkout@v2
+        with:
+          fetch-depth: 0 # Fetch all history for all branches and tags.
+      - uses: conda-incubator/setup-miniconda@v2
+        with:
+          channels: conda-forge
+          channel-priority: strict
+          mamba-version: "*"
+          auto-update-conda: false
+          python-version: "3.8"
+
+      - name: minimum versions policy
+        run: |
+          mamba install -y pyyaml conda
+          python ci/min_deps_check.py ci/requirements/py37-bare-minimum.yml
+          python ci/min_deps_check.py ci/requirements/py37-min-all-deps.yml

.github/workflows/ci-pre-commit.yml

@@ -0,0 +1,16 @@
+name: linting
+
+on:
+  push:
+    branches: "*"
+  pull_request:
+    branches: "*"
+
+jobs:
+  linting:
+    name: "pre-commit hooks"
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+      - uses: pre-commit/action@v2.0.0