CI: PRs build and test only the packages they touch (#1561)

Clippy, the test archive and the test shards cover the packages a PR changes plus their dependents. Main, nightly and manual runs stay full.

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

scripts/ci/affected.py

@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+"""Select the workspace packages a pull request affects.
+
+Usage: affected.py --paths FILE [--metadata FILE] [--github-output FILE]
+
+FILE holds the changed paths relative to the repository root, separated by NUL (git diff -z);
+"-" reads standard input. --metadata is the output of `cargo metadata --no-deps
+--format-version 1` (run on demand when omitted).
+
+Prints and optionally appends to $GITHUB_OUTPUT:
+  full=true|false   test the whole workspace
+  packages=a b c    the affected packages (empty when full, or when nothing needs building)
+
+A changed file maps to the package whose directory holds it. The packages that depend on those
+(directly or not, dev-dependencies included) are added. Anything that can change every package,
+or that no package owns, selects the full workspace. Only documentation and packaging files are
+ignored.
+"""
+import argparse
+import json
+import subprocess
+import sys
+
+# Changes here can affect every package.
+FULL_PREFIXES = (".cargo/", ".config/", ".github/", "vendor/", "tests/", "scripts/")
+FULL_FILES = ("Cargo.toml", "Cargo.lock")
+# Changes here affect no code: documentation and packaging.
+IGNORED_PREFIXES = ("docs/", "packaging/")
+# Root files that a crate embeds (include_str!), so they are not ignorable documentation.
+EMBEDDED = {"ATTRIBUTION.md": "solidcraft-ui-egui"}
+
+
+def load_metadata(path):
+    if path:
+        with open(path, encoding="utf-8") as f:
+            return json.load(f)
+    out = subprocess.run(
+        ["cargo", "metadata", "--no-deps", "--format-version", "1", "--locked"],
+        check=True, capture_output=True, text=True,
+    ).stdout
+    return json.loads(out)
+
+
+def read_paths(src):
+    data = sys.stdin.buffer.read() if src == "-" else open(src, "rb").read()
+    return [p.decode() for p in data.split(b"\0") if p]
+
+
+def select(meta, paths):
+    """Return (full, sorted package names)."""
+    root = meta["workspace_root"].rstrip("/") + "/"
+    pkgs = {}
+    for p in meta["packages"]:
+        manifest = p["manifest_path"]
+        assert manifest.startswith(root), manifest
+        pkgs[p["name"]] = manifest[len(root):].rsplit("/", 1)[0] + "/"
+    by_dir = {d: n for n, d in pkgs.items()}
+    # Reverse dependencies inside the workspace, matched by the dependency's path.
+    dependents = {n: set() for n in pkgs}
+    for p in meta["packages"]:
+        for d in p["dependencies"]:
+            path = d.get("path")
+            if not path:
+                continue
+            rel = path.rstrip("/") + "/"
+            target = by_dir.get(rel[len(root):]) if rel.startswith(root) else None
+            if target:
+                dependents[target].add(p["name"])
+
+    hit = set()
+    for path in paths:
+        if path in FULL_FILES or path.startswith(FULL_PREFIXES) or path.startswith("rust-toolchain"):
+            return True, []
+        owners = [d for d in by_dir if path.startswith(d)]
+        if owners:
+            hit.add(by_dir[max(owners, key=len)])
+        elif path in EMBEDDED:
+            hit.add(EMBEDDED[path])
+        elif path.startswith(IGNORED_PREFIXES) or ("/" not in path and path.endswith(".md")):
+            continue
+        else:
+            return True, []  # not owned by any package
+
+    todo, seen = list(hit), set(hit)
+    while todo:
+        for dep in dependents[todo.pop()]:
+            if dep not in seen:
+                seen.add(dep)
+                todo.append(dep)
+    return False, sorted(seen)
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--paths", required=True)
+    ap.add_argument("--metadata")
+    ap.add_argument("--github-output")
+    a = ap.parse_args()
+    full, packages = select(load_metadata(a.metadata), read_paths(a.paths))
+    lines = [f"full={'true' if full else 'false'}", f"packages={' '.join(packages)}"]
+    print("\n".join(lines))
+    if a.github_output:
+        with open(a.github_output, "a", encoding="utf-8") as f:
+            f.write("\n".join(lines) + "\n")
+
+
+if __name__ == "__main__":
+    main()