chore: fix luacov config, add manual coverage script

.gitignore

@@ -4,8 +4,8 @@
 /lua/output
 /lua/spec/snapshots/diffs
 /package-lock.json
-/luacov.report.out
-/luacov.stats.out
+luacov.report.out
+luacov.stats.out
 **/__pycache__/
 .env
 **/*.ck

lua/.luacov

@@ -1,8 +1,18 @@
 return {
 	configfile = '.luacov',
-	includeuntestedfiles = {'standard'},
-	include = {'standard/*'},
-	exclude = {'wikis/*'},
+	-- Report modules no spec ever loads as 0%, so coverage reflects all of commons
+	-- rather than only the files the suite happens to touch.
+	includeuntestedfiles = {'wikis/commons'},
+	include = {'wikis/commons/'},
+	exclude = {
+		'spec/',
+		'definitions/',
+		'3rd/',
+		'plugins/',
+		'test_assets/',
+		-- ScribuntoUnit testcases that run on-wiki, not under busted.
+		'wikis/commons/test/',
+	},
 	runreport = false, -- Don't work properly for some reason, have to do a manual `luacov` call afterwards
-	deletestats = true,
+	deletestats = false, -- Keep stats so the report can be regenerated / inspected after a run
 }

scripts/metrics/coverage.py

@@ -0,0 +1,103 @@
+"""Run the busted suite under luacov and report coverage of lua/wikis/commons.
+
+Coverage instrumentation is a per-line debug hook, so the suite takes roughly
+20x longer than normal -- expect a couple of minutes rather than a second.
+
+Needs busted and luacov on PATH, both for Lua 5.1:
+
+    luarocks install --lua-version=5.1 busted
+    luarocks install --lua-version=5.1 luacov
+
+Scope and exclusions come from lua/.luacov. Modules no spec ever loads count as
+0% rather than being left out, so the figure covers all of commons rather than
+only the files the suite happens to touch.
+
+Usage:
+    python scripts/metrics/coverage.py [--skip-run]
+"""
+
+import argparse
+import pathlib
+import re
+import subprocess
+import sys
+
+REPO_ROOT = pathlib.Path(__file__).resolve().parents[2]
+LUA_DIR = REPO_ROOT / "lua"
+REPORT = LUA_DIR / "luacov.report.out"
+
+TOTAL = re.compile(r"^Total\s+(\d+)\s+(\d+)\s+([\d.]+)%")
+FILE_ROW = re.compile(r"^wikis/commons/\S+\s+\d+\s+\d+\s+([\d.]+)%$")
+
+
+INSTALL_HINT = (
+    "not found on PATH. Install both for Lua 5.1:\n"
+    "  luarocks install --lua-version=5.1 busted\n"
+    "  luarocks install --lua-version=5.1 luacov"
+)
+
+
+def run(command, cwd):
+    try:
+        subprocess.run(command, cwd=cwd, check=True)
+    except FileNotFoundError:
+        raise SystemExit(f"{command[0]} {INSTALL_HINT}") from None
+    except subprocess.CalledProcessError as error:
+        raise SystemExit(f"{command[0]} failed (exit {error.returncode})") from None
+
+
+def run_suite():
+    """Run the test suite under coverage, then render the luacov report."""
+    run(["busted", "-C", "lua", "--run=ci", "-c"], REPO_ROOT)
+    run(["luacov"], LUA_DIR)
+
+
+def parse(report):
+    lines = report.read_text(encoding="utf-8", errors="replace").split("\n")
+    total = next((TOTAL.match(line) for line in lines if TOTAL.match(line)), None)
+    if total is None:
+        raise SystemExit(f"no Total line in {report}; did luacov run?")
+
+    shares = [m.group(1) for m in map(FILE_ROW.match, lines) if m]
+    return {
+        "hits": int(total.group(1)),
+        "missed": int(total.group(2)),
+        "coverage_pct": float(total.group(3)),
+        "files": len(shares),
+        "uncovered": sum(1 for s in shares if float(s) == 0),
+    }
+
+
+def table(m):
+    return [
+        "| Coverage (lua/wikis/commons) | |",
+        "|-|-|",
+        f"| Coverage | {m['coverage_pct']:.2f}% |",
+        f"| Lines hit | {m['hits']} |",
+        f"| Lines missed | {m['missed']} |",
+        f"| Files | {m['files']} |",
+        f"| Files at 0% | {m['uncovered']} |",
+    ]
+
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--skip-run",
+        action="store_true",
+        help="reuse the existing luacov report instead of re-running the suite",
+    )
+    args = parser.parse_args()
+
+    if not args.skip_run:
+        run_suite()
+    elif not REPORT.exists():
+        print(f"::error::no report at {REPORT}; run without --skip-run first")
+        return 1
+
+    print("\n".join(table(parse(REPORT))))
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())