run_one runs two recursive diffs over the same trees and only reads the first #129

• Repository: pingdotgg/ts-rust
• Target commit: 174f34ef377b7623ea48e1dacf35a8b90f5d9cee
• File: scripts/goport/compare-emit.sh:86

Summary

run_one in scripts/goport/compare-emit.sh first runs diff -rq into diffq.txt (the file the MATCH/DIFF verdict reads) and then unconditionally runs diff -r over the same two output trees into diff.txt. diff.txt is never read by the verdict, so every project pays for a second full recursive comparison; the duplicate was left in when the quick -rq pass was added and the old detailed pass was not removed.

Affected code

scripts/goport/compare-emit.sh:

   78    rm -rf "${OUT:?}/$n"; mkdir -p "$OUT/$n"
   79    s=$(date +%s)
   80    (cd "$cwd" && timeout 1200 "$bin" -p "$cfg" --outDir "$OUT/$n/out" --pretty false $flags > "$OUT/$n/log" 2> "$OUT/$n/err"); e=$?
   81    t=$(( $(date +%s) - s ))
   82    # Guard: neither tool may write into the project. Report any new file.
   83    leaked=$(find "$cwd" -newer "$stamp" -type f -not -path '*/node_modules/*' 2>/dev/null | head -5)
   84    [ -n "$leaked" ] && echo "$n WROTE-INTO-PROJECT: $leaked"
   85    mkdir -p "$OC/$n/out" "$OUT/$n/out"
   86    diff -rq "$OC/$n/out" "$OUT/$n/out" > "$OUT/$n/diffq.txt" 2>&1
   87    diff -r "$OC/$n/out" "$OUT/$n/out" > "$OUT/$n/diff.txt" 2>&1
   88    no=$(find "$OC/$n/out" -type f | wc -l); ng=$(find "$OUT/$n/out" -type f | wc -l)
   89    nd=$(grep -c '^Files .* differ$' "$OUT/$n/diffq.txt"); nonly=$(grep -c '^Only in' "$OUT/$n/diffq.txt")
   90    if [ "$nd" -eq 0 ] && [ "$nonly" -eq 0 ] && { [ "$no" -gt 0 ] || { [ "$ng" -eq 0 ] && [ "$e" = "$(cat "$OC/$n/rc")" ] &&
   91      cmp -s "$OC/$n/log" "$OUT/$n/log"; }; }; then m=MATCH; else m=DIFF; fi
   92    echo "$n $m oracle=$no goport=$ng differ=$nd only=$nonly rc=$e oracle_rc=$(cat "$OC/$n/rc") ${t}s panics=$(grep -c panic "$OUT/$n/err") unported=$(grep -c '^unported' "$OUT/$n/err")"
   93  }
   94  export -f run_one; export OC OUT bin ORACLE
   95  printf '%s\n' "${projects[@]}" | grep -E "^($filter)" | xargs -d '\n' -P "${JOBS:-4}" -I{} bash -c 'run_one "$@"' _ {} | tee "$OUT/summary.txt"
   96  ! grep -q ' DIFF ' "$OUT/summary.txt"

Expected behavior

The emit comparator needs at most one recursive comparison of the two emitted trees per project to determine MATCH/DIFF and write the summary; the second full diff is not part of the documented output contract.

Actual behavior

In scripts/goport/compare-emit.sh:86-87, every project comparison performs two recursive diffs over the same oracle and goport output trees; only the diff -rq output is used by the verdict at line 90, so the subsequent unconditional diff -r repeats expensive comparison work beyond the required cardinality.

How to reproduce

Run compare-emit.sh on one project with a diff wrapper that logs invocations; two recursive diffs target the same directories.

Root cause

run_one in scripts/goport/compare-emit.sh first runs diff -rq into diffq.txt (the file the MATCH/DIFF verdict reads) and then unconditionally runs diff -r over the same two output trees into diff.txt. diff.txt is never read by the verdict, so every project pays for a second full recursive comparison; the duplicate was left in when the quick -rq pass was added and the old detailed pass was not removed.

Suggested fix

Remove the unconditional diff -r into diff.txt (or make it conditional on diff -rq reporting differences) so the verdict uses a single recursive comparison:

diff -rq "$OC/$p/out" "$OUT/$p/out" > "$OUT/$p/diffq.txt" || true
# drop the duplicate diff -r

Keep the detailed diff only when the quick pass found differences.