only run tests if test code is changed

.github/workflows/test.yml

@@ -8,10 +8,31 @@ concurrency:
   group: test-${{github.ref}}
   cancel-in-progress: true
 jobs:
+  check-changes:
+    name: Check for changes
+    runs-on: ubuntu-latest
+    outputs:
+      changed: ${{steps.check-for-changes.outputs.changed}}
+    steps:
+      - name: 🛒 Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - id: check-for-changes
+        run: |
+          gh pr diff --name-only |grep '^lenskit.*\.py$'
+          if [ "$?" -eq 0 ]; then
+              echo changed=true >>$GITHUB_OUTPUT
+          else
+              echo changed=false >>$GITHUB_OUTPUT
+          fi
   conda:
     name: Conda Python ${{matrix.python}} on ${{matrix.platform}}
     runs-on: ${{matrix.platform}}
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     defaults:
       run:
         shell: bash -el {0}
@@ -71,6 +92,9 @@ jobs:
     name: Vanilla Python ${{matrix.python}} on ${{matrix.platform}}
     runs-on: ${{matrix.platform}}
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     strategy:
       fail-fast: false
       matrix:
@@ -129,6 +153,9 @@ jobs:
     name: Non-JIT test coverage
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -179,6 +206,9 @@ jobs:
     name: Minimal dependency tests
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -226,6 +256,9 @@ jobs:
     name: FunkSVD tests on Python ${{matrix.python}}
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     defaults:
       run:
         shell: bash -el {0}
@@ -281,6 +314,9 @@ jobs:
     name: Minimal dependency tests for FunkSVD
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -328,6 +364,9 @@ jobs:
     name: Implicit bridge tests on Python ${{matrix.python}}
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     defaults:
       run:
         shell: bash -el {0}
@@ -383,6 +422,9 @@ jobs:
     name: Minimal dependency tests for Implicit
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     steps:
       - name: 🛒 Checkout
         uses: actions/checkout@v4
@@ -430,6 +472,9 @@ jobs:
     name: HPF bridge tests on Python ${{matrix.python}}
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    needs:
+      - check-changes
+    if: jobs.check-changes.outputs.changed
     strategy:
       fail-fast: false
       matrix:
@@ -592,6 +637,7 @@ jobs:
     name: Test suite results
     runs-on: ubuntu-latest
     needs:
+      - check-changes
       - conda
       - vanilla
       - nojit

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

@@ -12,7 +12,8 @@
 
 
 def workflow():
-    jobs: dict[str, GHJob] = jobs_test_matrix()
+    jobs = {"check-changes": job_check_changes()}
+    jobs.update(jobs_test_matrix())
     jobs["results"] = jobs_result(list(jobs.keys()))
     return {
         "name": "Automatic Tests",
@@ -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": "jobs.check-changes.outputs.changed",
     }
     if options.env == "conda":
         job["defaults"] = {
@@ -355,6 +358,28 @@ def test_doc_job() -> GHJob:
     }
 
 
+def job_check_changes() -> GHJob:
+    return {
+        "name": "Check for changes",
+        "runs-on": "ubuntu-latest",
+        "outputs": {"changed": "${{steps.check-for-changes.outputs.changed}}"},
+        "steps": [
+            step_checkout(),
+            {
+                "id": "check-for-changes",
+                "run": script("""
+                    gh pr diff --name-only |grep '^lenskit.*\\.py$'
+                    if [ "$?" -eq 0 ]; then
+                        echo changed=true >>$GITHUB_OUTPUT
+                    else
+                        echo changed=false >>$GITHUB_OUTPUT
+                    fi
+                """),
+            },
+        ],
+    }
+
+
 def jobs_test_matrix() -> dict[str, GHJob]:
     return {
         "conda": test_job(