ci: Reduce rust coverage report delay (#1370)

CI was running tests on `{MSRV, beta, nightly}` first, and only then
running tests with coverage instrumentation on nightly.

Since those tests are not on the critical path for the required checks,
we can run the nightly tests directly with instrumentation on the first
pass, shaving ~2mins from the commit-to-codecov report delay.

I'm only doing this for rust, as the python tests _are_ in the required
checks sets and we don't want to slow down those.

drive-by: The python tests job had the same name as the linting job.

---------

Co-authored-by: Douglas Wilson <[email protected]>

.github/workflows/ci-py.yml

@@ -95,7 +95,7 @@ jobs:
   test:
     needs: [changes, build_binary]
     if: ${{ needs.changes.outputs.python == 'true' }}
-    name: check python ${{ matrix.python-version }}
+    name: test python ${{ matrix.python-version }}
     runs-on: ubuntu-latest
 
     strategy:

.github/workflows/ci-rs.yml

@@ -123,7 +123,9 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        rust: ['1.75', beta, 'nightly']
+        # Stable is covered by `tests-stable-no-features` and `tests-stable-all-features`
+        # Nightly is covered by `tests-nightly-coverage`
+        rust: ['1.75', beta]
     name: tests (Rust ${{ matrix.rust }})
     steps:
       - uses: actions/checkout@v4
@@ -143,37 +145,12 @@ jobs:
       - name: Tests with all features
         run: cargo test --verbose --workspace --all-features
 
-  # This is a meta job to mark successful completion of the required checks,
-  # even if they are skipped due to no changes in the relevant files.
-  required-checks:
-    name: Required checks 🦀
-    needs: [changes, check, tests-stable-no-features, tests-stable-all-features]
-    if: ${{ !cancelled() }}
-    runs-on: ubuntu-latest
-    steps:
-      - name: Fail if required checks failed
-        # This condition should simply be `if: failure() || cancelled()`,
-        # but there seems to be a bug in the github workflow runner.
-        #
-        # See https://github.com/orgs/community/discussions/80788
-        if: |
-          needs.changes.result == 'failure' || needs.changes.result == 'cancelled' ||
-          needs.check.result == 'failure' || needs.check.result == 'cancelled' ||
-          needs.tests-stable-no-features.result == 'failure' || needs.tests-stable-no-features.result == 'cancelled' ||
-          needs.tests-stable-all-features.result == 'failure' || needs.tests-stable-all-features.result == 'cancelled'
-        run: |
-          echo "Required checks failed"
-          echo "Please check the logs for more information"
-          exit 1
-      - name: Pass if required checks passed
-        run: |
-          echo "All required checks passed"
-
-  coverage:
-    needs: [changes, tests-stable-no-features, tests-stable-all-features, tests-other, check]
-    # Run only if there are changes in the relevant files and the check job passed or was skipped
-    if: always() && !failure() && !cancelled() && needs.changes.outputs.rust == 'true' && github.event_name != 'merge_group'
+  tests-nightly-coverage:
+    needs: changes
+    # Run only if there are changes in the relevant files
+    if: ${{ needs.changes.outputs.rust == 'true' && github.event_name != 'merge_group' }}
     runs-on: ubuntu-latest
+    name: tests (Rust nightly, coverage)
     steps:
       - uses: actions/checkout@v4
       - uses: mozilla-actions/[email protected]
@@ -198,3 +175,29 @@ jobs:
           name: rust
           flags: rust
           token: ${{ secrets.CODECOV_TOKEN }}
+
+  # This is a meta job to mark successful completion of the required checks,
+  # even if they are skipped due to no changes in the relevant files.
+  required-checks:
+    name: Required checks 🦀
+    needs: [changes, check, tests-stable-no-features, tests-stable-all-features]
+    if: ${{ !cancelled() }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: Fail if required checks failed
+        # This condition should simply be `if: failure() || cancelled()`,
+        # but there seems to be a bug in the github workflow runner.
+        #
+        # See https://github.com/orgs/community/discussions/80788
+        if: |
+          needs.changes.result == 'failure' || needs.changes.result == 'cancelled' ||
+          needs.check.result == 'failure' || needs.check.result == 'cancelled' ||
+          needs.tests-stable-no-features.result == 'failure' || needs.tests-stable-no-features.result == 'cancelled' ||
+          needs.tests-stable-all-features.result == 'failure' || needs.tests-stable-all-features.result == 'cancelled'
+        run: |
+          echo "Required checks failed"
+          echo "Please check the logs for more information"
+          exit 1
+      - name: Pass if required checks passed
+        run: |
+          echo "All required checks passed"