From 096d49af6ac025637baf873558e8ffc2068c5da0 Mon Sep 17 00:00:00 2001
From: Kyle Sexton <153232337+kyle-sexton@users.noreply.github.com>
Date: Wed, 28 Oct 2026 00:12:51 -0400
Subject: [PATCH] fix(scripts): keep a caller's CHECK_DATA_ROOT out of
 check-affected's test suites

When CHECK_DATA_ROOT names the script's own tree, as the ready step's verify
one-liner passes it from another checkout, check-affected left it exported, so
every test suite inherited it and read the PR tree in place of its fixture
repository: check-comment-hygiene.test.sh and check-affected.test.sh failed
and the gate recorded fail. Unset it when it names this tree.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 scripts/check-affected.sh      |  4 ++++
 scripts/check-affected.test.sh | 10 ++++++++++
 2 files changed, 14 insertions(+)

diff --git a/scripts/check-affected.sh b/scripts/check-affected.sh
index a318b231f73..cfcdd7e0a86 100755
--- a/scripts/check-affected.sh
+++ b/scripts/check-affected.sh
@@ -204,6 +204,10 @@ if [[ "$(pwd -P)" != "$tools" ]]; then
   export CHECK_DATA_ROOT="$PWD"
   # uvx would otherwise read a uv.toml or [tool.uv] index from the checked tree.
   export UV_NO_CONFIG=1
+else
+  # It names this tree, so it says nothing; the test suites build fixture
+  # repositories, and an inherited one would point them back here.
+  unset CHECK_DATA_ROOT
 fi
 
 gates_file="$tools/scripts/check-affected-gates.txt"
diff --git a/scripts/check-affected.test.sh b/scripts/check-affected.test.sh
index 17638c25c1c..59219ae8241 100755
--- a/scripts/check-affected.test.sh
+++ b/scripts/check-affected.test.sh
@@ -36,6 +36,7 @@ done
 cat >"$repo/scripts/affected-tests.sh" <<'STUB'
 #!/usr/bin/env bash
 echo "affected-tests ran" >&2
+[[ -z "${STUB_ENV_LOG:-}" ]] || printf '%s' "${CHECK_DATA_ROOT-unset}" >"$STUB_ENV_LOG"
 while (($#)); do
   [[ "$1" == --write-not-run ]] && printf '%s' "${STUB_NOT_RUN:-}" >"$2"
   shift
@@ -124,6 +125,15 @@ run_from() {
 run_from "$other" --base base --tests
 check "run from another checkout, it lists the script's own branch's change" \
   '[[ $RC == 0 && $OUT == *"over 1 changed files"* && $ERR != *"SKIP tests"* ]]'
+# The ready step names the script's own tree in CHECK_DATA_ROOT from another
+# checkout. The suites build fixture repositories of their own, so the variable
+# must not reach them, or each one reads this tree in place of its fixture.
+RC=0
+OUT="$(cd "$other" && CHECK_DATA_ROOT="$repo" STUB_ENV_LOG="$tmp/env.log" \
+  bash "$repo/scripts/check-affected.sh" --base base --tests 2>"$tmp/err")" || RC=$?
+ERR="$(cat "$tmp/err")"
+check "CHECK_DATA_ROOT naming the script's own tree checks that tree and is not passed to the suites" \
+  '[[ $RC == 0 && $OUT == *"over 1 changed files"* && $(cat "$tmp/env.log") == unset ]]'
 git_test_config "$repo" update-ref refs/remotes/origin/main "$(git_test_config "$repo" rev-parse base)"
 run_from "$other" --base origin/main --no-fetch
 check "an explicit --base run from another checkout still lists the change" \