Add validate-feed helper script

AGENTS.md

@@ -81,12 +81,14 @@ The only way for actions to affect the view returned by the render-fn running in
 - Sync Python dependencies with `uv sync --all-groups`.
 - Run the app with `uv run repub`.
 - Generate CSS with `tailwindcss -i ./repub/static/app.tailwind.css -o ./repub/static/app.css` and add `--watch` when you need live rebuilds.
+- Validate a generated feed with `./scripts/validate-feed path/to/feed.rss`. This wraps the local checkout at `~/src/github.com/w3c/feedvalidator` and pages the validator output through `less` by default.
 
 ```sh
 uv sync --all-groups
 uv run pytest
 uv run flake8 repub/ tests/
 uv run pyright
+./scripts/validate-feed out/feeds/mn-cuba/feed.rss
 nix fmt
 nix flake check
 uv run repub

scripts/validate-feed

@@ -0,0 +1,11 @@
+#!/bin/sh
+set -eu
+
+feedvalidator_dir="${FEEDVALIDATOR_DIR:-$HOME/src/github.com/w3c/feedvalidator}"
+pager="${PAGER:-less}"
+
+feed_path="$(realpath "$1")"
+shift
+
+cd "$feedvalidator_dir"
+uv run validate_feed.py "$feed_path" "$@" | "$pager"

tests/test_validate_feed_script.py

@@ -0,0 +1,67 @@
+import os
+import stat
+import subprocess
+from pathlib import Path
+
+
+def test_validate_feed_script_changes_to_feedvalidator_and_forwards_args(
+    tmp_path: Path,
+) -> None:
+    script_path = Path(__file__).resolve().parents[1] / "scripts" / "validate-feed"
+    feedvalidator_dir = tmp_path / "feedvalidator"
+    bin_dir = tmp_path / "bin"
+    caller_dir = tmp_path / "caller"
+    feed_path = caller_dir / "path" / "to" / "feed.rss"
+    trace_dir = tmp_path / "trace"
+
+    feedvalidator_dir.mkdir()
+    bin_dir.mkdir()
+    feed_path.parent.mkdir(parents=True)
+    feed_path.write_text("<rss/>", encoding="utf-8")
+    trace_dir.mkdir()
+
+    uv_path = bin_dir / "uv"
+    uv_path.write_text(
+        """#!/bin/sh
+printf '%s\\n' "$PWD" > "$TRACE_DIR/cwd"
+printf '%s\\n' "$@" > "$TRACE_DIR/args"
+printf 'validator output\\n'
+""",
+        encoding="utf-8",
+    )
+    uv_path.chmod(uv_path.stat().st_mode | stat.S_IXUSR)
+
+    pager_path = bin_dir / "pager"
+    pager_path.write_text(
+        """#!/bin/sh
+cat > "$TRACE_DIR/pager-input"
+""",
+        encoding="utf-8",
+    )
+    pager_path.chmod(pager_path.stat().st_mode | stat.S_IXUSR)
+
+    env = os.environ.copy()
+    env["FEEDVALIDATOR_DIR"] = str(feedvalidator_dir)
+    env["PAGER"] = str(pager_path)
+    env["PATH"] = f"{bin_dir}:{env['PATH']}"
+    env["TRACE_DIR"] = str(trace_dir)
+
+    subprocess.run(
+        [str(script_path), "path/to/feed.rss", "--flag"],
+        check=True,
+        env=env,
+        cwd=caller_dir,
+    )
+
+    assert (trace_dir / "cwd").read_text(encoding="utf-8").strip() == str(
+        feedvalidator_dir
+    )
+    assert (trace_dir / "args").read_text(encoding="utf-8").splitlines() == [
+        "run",
+        "validate_feed.py",
+        str(feed_path.resolve()),
+        "--flag",
+    ]
+    assert (trace_dir / "pager-input").read_text(
+        encoding="utf-8"
+    ) == "validator output\n"