Only run tests when the PR changes test code

.github/workflows/test.yml

@@ -8,10 +8,45 @@ concurrency:
   group: test-${{github.ref}}
   cancel-in-progress: true
 jobs:
+  check-changes:
+    name: Check for changes
+    runs-on: ubuntu-latest
+    outputs:
+      changed: ${{steps.check-for-changes.outputs.changed}}
+    steps:
+      - name: 🛒 Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - id: check-for-changes
+        name: 🔎 Check for changes
+        run: |
+          if [[ -z "$PR_NUMBER" ]]; then
+              echo "not a PR, assuming changed"
+              echo changed=yes >>"$GITHUB_OUTPUT"
+          else
+              if gh pr diff $PR_NUMBER --name-only |grep '^lenskit.*\.py$'; then
+                  echo "source code changed"
+                  echo changed=yes >>"$GITHUB_OUTPUT"
+              elif gh pr view $PR_NUMBER --json body -t '{{.body}}' | grep 'tests: force'; then
+                  echo "test run forced from PR text"
+                  echo changed=yes >>"$GITHUB_OUTPUT"
+              else
+                  echo "source code unchanged"
+                  echo changed=no >>"$GITHUB_OUTPUT"
+              fi
+          fi
+          cat $GITHUB_OUTPUT
+        env:
+          GH_TOKEN: ${{ github.token }}
+          PR_NUMBER: ${{ github.event.number }}
   conda:
     name: Conda Python ${{matrix.python}} on ${{matrix.platform}}
     runs-on: ${{matrix.platform}}
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     defaults:
       run:
         shell: bash -el {0}
@@ -71,6 +106,9 @@ jobs:
     name: Vanilla Python ${{matrix.python}} on ${{matrix.platform}}
     runs-on: ${{matrix.platform}}
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     strategy:
       fail-fast: false
       matrix:
@@ -129,6 +167,9 @@ jobs:
     name: Non-JIT test coverage
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -179,6 +220,9 @@ jobs:
     name: Minimal dependency tests
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -226,6 +270,9 @@ jobs:
     name: FunkSVD tests on Python ${{matrix.python}}
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     defaults:
       run:
         shell: bash -el {0}
@@ -281,6 +328,9 @@ jobs:
     name: Minimal dependency tests for FunkSVD
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -328,6 +378,9 @@ jobs:
     name: Implicit bridge tests on Python ${{matrix.python}}
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     defaults:
       run:
         shell: bash -el {0}
@@ -383,6 +436,9 @@ jobs:
     name: Minimal dependency tests for Implicit
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -430,6 +486,9 @@ jobs:
     name: HPF bridge tests on Python ${{matrix.python}}
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     strategy:
       fail-fast: false
       matrix:
@@ -486,6 +545,9 @@ jobs:
     defaults:
       run:
         shell: bash -el {0}
+    needs:
+      - check-changes
+    if: needs.check-changes.outputs.changed == 'yes'
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -592,6 +654,7 @@ jobs:
     name: Test suite results
     runs-on: ubuntu-latest
     needs:
+      - check-changes
       - conda
       - vanilla
       - nojit

.gitignore

@@ -23,6 +23,7 @@ dask-worker-space/
 .tox/
 .vagrant/
 .venv/
+.uv/
 scratch/
 
 # build outputs

lkdev/ghactions.py

@@ -60,6 +60,8 @@ def command(cls, args: list[str]):
     {
         "name": str,
         "runs-on": str,
+        "if": NotRequired[str],
+        "outputs": NotRequired[dict[str, str]],
         "timeout-minutes": NotRequired[int],
         "strategy": NotRequired[dict[str, Any]],
         "defaults": NotRequired[dict[str, Any]],

lkdev/workflows/test.py

@@ -12,8 +12,9 @@
 
 
 def workflow():
-    jobs: dict[str, GHJob] = test_jobs()
-    jobs["results"] = result_job(list(jobs.keys()))
+    jobs = {"check-changes": job_check_changes()}
+    jobs.update(jobs_test_matrix())
+    jobs["results"] = jobs_result(list(jobs.keys()))
     return {
         "name": "Automatic Tests",
         "on": {
@@ -286,6 +287,8 @@ def test_job(options: JobOptions) -> GHJob:
         "name": options.name,
         "runs-on": options.vm_platform,
         "timeout-minutes": 30,
+        "needs": ["check-changes"],
+        "if": "needs.check-changes.outputs.changed == 'yes'",
     }
     if options.env == "conda":
         job["defaults"] = {
@@ -312,6 +315,8 @@ def test_eval_job() -> GHJob:
         "name": opts.name,
         "runs-on": opts.vm_platform,
         "defaults": {"run": {"shell": "bash -el {0}"}},
+        "needs": ["check-changes"],
+        "if": "needs.check-changes.outputs.changed == 'yes'",
         "steps": [step_checkout(opts)]
         + steps_setup_conda(opts)
         + steps_mldata(opts, ["ml-100k", "ml-20m"])
@@ -355,7 +360,44 @@ def test_doc_job() -> GHJob:
     }
 
 
-def test_jobs() -> dict[str, GHJob]:
+def job_check_changes() -> GHJob:
+    return {
+        "name": "Check for changes",
+        "runs-on": "ubuntu-latest",
+        "outputs": {"changed": "${{steps.check-for-changes.outputs.changed}}"},
+        "steps": [
+            step_checkout(),
+            {
+                "id": "check-for-changes",
+                "name": "🔎 Check for changes",
+                "run": script("""
+                    if [[ -z "$PR_NUMBER" ]]; then
+                        echo "not a PR, assuming changed"
+                        echo changed=yes >>"$GITHUB_OUTPUT"
+                    else
+                        if gh pr diff $PR_NUMBER --name-only |grep '^lenskit.*\\.py$'; then
+                            echo "source code changed"
+                            echo changed=yes >>"$GITHUB_OUTPUT"
+                        elif gh pr view $PR_NUMBER --json body -t '{{.body}}' | grep 'tests: force'; then
+                            echo "test run forced from PR text"
+                            echo changed=yes >>"$GITHUB_OUTPUT"
+                        else
+                            echo "source code unchanged"
+                            echo changed=no >>"$GITHUB_OUTPUT"
+                        fi
+                    fi
+                    cat $GITHUB_OUTPUT
+                """),  # noqa: E501
+                "env": {
+                    "GH_TOKEN": "${{ github.token }}",
+                    "PR_NUMBER": "${{ github.event.number }}",
+                },
+            },
+        ],
+    }
+
+
+def jobs_test_matrix() -> dict[str, GHJob]:
     return {
         "conda": test_job(
             JobOptions(
@@ -436,7 +478,7 @@ def test_jobs() -> dict[str, GHJob]:
     }
 
 
-def result_job(deps: list[str]) -> GHJob:
+def jobs_result(deps: list[str]) -> GHJob:
     return {
         "name": "Test suite results",
         "runs-on": "ubuntu-latest",