Fix watch tests that flake on duplicate change events

rewatch-ocaml/tests/check_command_validation.sh

@@ -1517,6 +1517,14 @@ for implementation in rust ocaml; do
   fi
   normalize_project_path "$work/quiet-watch-$implementation.err" \
     "$work/quiet-watch-$implementation.err.norm" "$quiet_watch_project"
+  # macOS and Windows can report one write as several change events, and each
+  # rebuild reports the parse error again. Compare the distinct reports only.
+  node -e '
+    const fs = require("fs");
+    const blocks = fs.readFileSync(process.argv[1], "utf8").split(/^(?=Error in )/m);
+    const distinct = blocks.filter((block, i) => block !== blocks[i - 1]);
+    fs.writeFileSync(process.argv[1], distinct.join(""));
+  ' "$work/quiet-watch-$implementation.err.norm"
 done
 if ! cmp -s "$work/quiet-watch-rust.err.norm" \
   "$work/quiet-watch-ocaml.err.norm"; then

rewatch-ocaml/tests/run.sh

@@ -1923,10 +1923,25 @@ background_pids="$background_pids $retained_parse_pid"
 wait_for_initial_build "$retained_parse/watch.log"
 printf 'let value =\n' >"$retained_parse/src/A.res"
 wait_for_text "$retained_parse/watch.log" 'This let-binding misses an expression'
+# Windows can report one write as several change events, and each one starts
+# a rebuild that parses A and reports its error again. Wait until those
+# rebuilds are over, so that the counts only grow from the edit of B.
 failed_parses=$(grep -c '^parse.*A\.res' "$retained_parse/calls.log")
+quiet_polls=0
+while [ "$quiet_polls" -lt 10 ]; do
+  sleep 0.1
+  parses=$(grep -c '^parse.*A\.res' "$retained_parse/calls.log")
+  if [ "$parses" = "$failed_parses" ]; then
+    quiet_polls=$((quiet_polls + 1))
+  else
+    failed_parses=$parses
+    quiet_polls=0
+  fi
+done
+reported_errors=$(grep -c 'This let-binding misses an expression' "$retained_parse/watch.log")
 printf 'let other = 2\n' >"$retained_parse/src/B.res"
-wait_for_text "$retained_parse/watch.log" 'This let-binding misses an expression' 2
-test "$(grep -c '^parse.*A\.res' "$retained_parse/calls.log")" -gt "$failed_parses"
+wait_for_count "$retained_parse/calls.log" '^parse.*A\.res' $((failed_parses + 1))
+wait_for_text "$retained_parse/watch.log" 'This let-binding misses an expression' $((reported_errors + 1))
 grep 'value = 1' "$retained_parse/src/A.js" >/dev/null
 printf 'let value = 2\n' >"$retained_parse/src/A.res"
 wait_for_text "$retained_parse/src/A.js" 'value = 2'