[CI] Dectect changes to trigger only necessary jobs

.github/workflows/main_workflow.yml

@@ -11,6 +11,31 @@ on:
         description: "Whether to run the light CI"
         required: true
         type: boolean
+      # check_cpp:
+      #   description: "Whether C++ sources changed in the PR diff"
+      #   required: false
+      #   default: true
+      #   type: boolean
+      # run_sph_tests:
+      #   description: "Whether to run SPH-related CI (core or shammodels/sph changes)"
+      #   required: false
+      #   default: true
+      #   type: boolean
+      # run_ramses_tests:
+      #   description: "Whether to run Ramses-related CI (core or shammodels/ramses changes)"
+      #   required: false
+      #   default: true
+      #   type: boolean
+      # run_zeus_tests:
+      #   description: "Whether to run Zeus-related CI (core or shammodels/zeus changes)"
+      #   required: false
+      #   default: true
+      #   type: boolean
+      # run_gsph_tests:
+      #   description: "Whether to run GSPH-related CI (core or shammodels/gsph changes)"
+      #   required: false
+      #   default: true
+      #   type: boolean
     secrets:
       CODECOV_TOKEN:
         description: "Codecov upload token"

.github/workflows/on_pr.yml

@@ -11,12 +11,37 @@ concurrency:
 
 jobs:
 
+  detect_ci_flags:
+    name: Detect CI flags
+    runs-on: ubuntu-latest
+    outputs:
+      check_cpp: ${{ steps.flags.outputs.check_cpp }}
+      run_sph_tests: ${{ steps.flags.outputs.run_sph_tests }}
+      run_ramses_tests: ${{ steps.flags.outputs.run_ramses_tests }}
+      run_zeus_tests: ${{ steps.flags.outputs.run_zeus_tests }}
+      run_gsph_tests: ${{ steps.flags.outputs.run_gsph_tests }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Diff against PR base
+        run: git diff ${{ github.event.pull_request.base.sha }} HEAD > pr.diff
+      - name: Detect flags
+        id: flags
+        run: python3 tools/detect_ci_flags.py --diff pr.diff --github-output "$GITHUB_OUTPUT"
+
   main_workflow:
     name: CI
+    needs: [detect_ci_flags]
     uses: ./.github/workflows/main_workflow.yml
     with:
       run_build_push_docker: true
       light_ci: ${{ contains(github.event.pull_request.labels.*.name, 'light-ci') }}
+      # check_cpp: ${{ needs.detect_ci_flags.outputs.check_cpp == 'true' }}
+      # run_sph_tests: ${{ needs.detect_ci_flags.outputs.run_sph_tests == 'true' }}
+      # run_ramses_tests: ${{ needs.detect_ci_flags.outputs.run_ramses_tests == 'true' }}
+      # run_zeus_tests: ${{ needs.detect_ci_flags.outputs.run_zeus_tests == 'true' }}
+      # run_gsph_tests: ${{ needs.detect_ci_flags.outputs.run_gsph_tests == 'true' }}
 
   light_ci:
     name: Notify Light CI

tools/detect_ci_flags.py

@@ -0,0 +1,112 @@
+"""Detect CI flags from a unified diff against the PR base."""
+
+import argparse
+import re
+import sys
+from pathlib import Path
+
+MODELS = ("sph", "ramses", "zeus", "gsph")
+
+DIFF_PATH_RE = re.compile(r"^(?:---|\+\+\+)\s+(?:a/|b/)?(.+?)\s*$")
+
+
+def parse_changed_paths(diff_text: str) -> set[str]:
+    paths: set[str] = set()
+    for line in diff_text.splitlines():
+        match = DIFF_PATH_RE.match(line)
+        if not match:
+            continue
+        path = match.group(1)
+        if path == "/dev/null":
+            continue
+        paths.add(path)
+    return paths
+
+
+def is_cpp_path(path: str) -> bool:
+    return path.endswith(".cpp") or path.endswith(".hpp")
+
+
+def is_under_prefix(path: str, prefix: str) -> bool:
+    normalized = path.replace("\\", "/")
+    return normalized == prefix or normalized.startswith(prefix + "/")
+
+
+def is_model_specific_path(path: str) -> bool:
+    normalized = path.replace("\\", "/")
+    for model in MODELS:
+        if is_under_prefix(normalized, f"src/shammodels/{model}"):
+            return True
+        if is_under_prefix(normalized, f"src/tests/shammodels/{model}"):
+            return True
+    return False
+
+
+def is_core_component_path(path: str) -> bool:
+    normalized = path.replace("\\", "/")
+    if not is_under_prefix(normalized, "src"):
+        return False
+    return not is_model_specific_path(normalized)
+
+
+def is_model_path(path: str, model: str) -> bool:
+    normalized = path.replace("\\", "/")
+    return is_under_prefix(normalized, f"src/shammodels/{model}") or is_under_prefix(
+        normalized, f"src/tests/shammodels/{model}"
+    )
+
+
+def evaluate_flags(paths: set[str]) -> dict[str, bool]:
+    check_cpp = any(is_cpp_path(p) for p in paths)
+
+    flags = {
+        "check_cpp": check_cpp,
+        "run_sph_tests": any(is_core_component_path(p) or is_model_path(p, "sph") for p in paths),
+        "run_ramses_tests": any(
+            is_core_component_path(p) or is_model_path(p, "ramses") for p in paths
+        ),
+        "run_zeus_tests": any(is_core_component_path(p) or is_model_path(p, "zeus") for p in paths),
+        "run_gsph_tests": any(is_core_component_path(p) or is_model_path(p, "gsph") for p in paths),
+    }
+    return flags
+
+
+def write_github_output(flags: dict[str, bool], output_path: str) -> None:
+    with open(output_path, "a", encoding="utf-8") as out:
+        out.writelines(f"{name}={str(value).lower()}\n" for name, value in flags.items())
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Detect CI flags from a PR diff.")
+    parser.add_argument("--diff", required=True, help="Path to unified diff file.")
+    parser.add_argument(
+        "--github-output",
+        help="Path to GITHUB_OUTPUT file for workflow job outputs.",
+    )
+    args = parser.parse_args()
+
+    diff_path = Path(args.diff)
+    if not diff_path.exists():
+        print(f"error: diff file not found: {args.diff}", file=sys.stderr)
+        return 1
+
+    diff_text = diff_path.read_text(encoding="utf-8", errors="replace")
+    paths = parse_changed_paths(diff_text)
+    flags = evaluate_flags(paths)
+
+    print(f"Changed paths ({len(paths)}):")
+    for path in sorted(paths):
+        print(f"  {path}")
+
+    print("CI flags:")
+    for name, value in flags.items():
+        print(f"  {name}={value}")
+
+    if args.github_output:
+        write_github_output(flags, args.github_output)
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())