From c28f2b70db8e592ca3d2fc86379346f379af2980 Mon Sep 17 00:00:00 2001
From: Cassidy Marble <cassidy@marble.sh>
Date: Tue, 6 Oct 2026 14:01:11 -0300
Subject: [PATCH] [Perf] `nvm_npmrc_bad_news_bears`: scan npmrc files without
 forking `grep`

---
 nvm.sh                                 | 23 +++++++++++-
 test/fast/Unit tests/nvm_die_on_prefix | 51 ++++++++++++++++++++++++++
 2 files changed, 72 insertions(+), 2 deletions(-)

diff --git a/nvm.sh b/nvm.sh
index ed24ed1c..180d349c 100755
--- a/nvm.sh
+++ b/nvm.sh
@@ -3329,9 +3329,28 @@ nvm_npm_global_modules() {
 
 nvm_npmrc_bad_news_bears() {
   local NVM_NPMRC
+  local NVM_NPMRC_LINE
+  local NVM_NPMRC_KEY
   NVM_NPMRC="${1-}"
-  if [ -n "${NVM_NPMRC}" ] && [ -f "${NVM_NPMRC}" ] && nvm_grep -Ee '^(prefix|globalconfig) *=' <"${NVM_NPMRC}" >/dev/null; then
-    return 0
+  if [ -n "${NVM_NPMRC}" ] && [ -f "${NVM_NPMRC}" ]; then
+    # this is fork-free on purpose: it runs up to four times on every `nvm use`/`nvm install`
+    # avoid grepping or sub-shells as much as possible here.
+    while IFS= read -r NVM_NPMRC_LINE || [ -n "${NVM_NPMRC_LINE}" ]; do
+      case "${NVM_NPMRC_LINE}" in
+        *=*)
+          NVM_NPMRC_KEY="${NVM_NPMRC_LINE%%=*}"
+        ;;
+        *)
+          continue
+        ;;
+      esac
+      NVM_NPMRC_KEY="${NVM_NPMRC_KEY%"${NVM_NPMRC_KEY##*[! ]}"}"
+      case "${NVM_NPMRC_KEY}" in
+        prefix | globalconfig)
+          return 0
+        ;;
+      esac
+    done < "${NVM_NPMRC}"
   fi
   return 1
 }
diff --git a/test/fast/Unit tests/nvm_die_on_prefix b/test/fast/Unit tests/nvm_die_on_prefix
index b16b0dc4..8c1f3884 100755
--- a/test/fast/Unit tests/nvm_die_on_prefix	
+++ b/test/fast/Unit tests/nvm_die_on_prefix	
@@ -201,4 +201,55 @@ Run \`foo\` to unset it."
   [ "_$CAPTURED_EXIT_CODE" = "_10" ] || die "'nvm_die_on_prefix 0 foo' with user .npmrc that has globalconfig did not exit with 10; got '$CAPTURED_EXIT_CODE'"
 )
 
+# nvm_npmrc_bad_news_bears matches `^(prefix|globalconfig) *=`
+NPMRC="${TEST_DIR}/bad-news.npmrc"
+printf 'prefix=x\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefix=x should be bad news'
+printf 'prefix =x\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefix =x should be bad news'
+printf 'prefix  =x\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefix  =x should be bad news'
+printf 'prefix =\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefix = should be bad news'
+printf 'foo=1\nprefix = y\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'a matching line after a non-matching line should be bad news'
+printf 'prefix=x' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefix=x without a trailing newline should be bad news'
+printf 'globalconfig=x\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'globalconfig=x should be bad news'
+printf 'globalconfig = x\n' > "${NPMRC}"
+nvm_npmrc_bad_news_bears "${NPMRC}" || die 'globalconfig = x should be bad news'
+
+printf 'prefixfoo=x\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefixfoo=x should not be bad news'
+printf 'globalconfigfoo=x\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'globalconfigfoo=x should not be bad news'
+printf 'prefix x=x\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'prefix x=x should not be bad news'
+printf 'prefix\t=x\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'a tab before = should not be bad news'
+printf ' prefix=x\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'a leading space should not be bad news'
+printf 'Prefix=x\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'an uppercase key should not be bad news'
+printf 'prefix\n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'a bare prefix should not be bad news'
+printf 'prefix   \n' > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'trailing spaces without = should not be bad news'
+: > "${NPMRC}"
+! nvm_npmrc_bad_news_bears "${NPMRC}" || die 'an empty npmrc should not be bad news'
+! nvm_npmrc_bad_news_bears || die 'a missing argument should not be bad news'
+! nvm_npmrc_bad_news_bears "${TEST_DIR}/nonexistent.npmrc" || die 'a missing file should not be bad news'
+
+# the npmrc scan must not fork `grep`
+(
+  rm -f "${TEST_DIR}/grep-was-called"
+  nvm_grep() { : > "${TEST_DIR}/grep-was-called"; return 1; }
+  printf 'globalconfig = nope\n' > "${TEST_DIR}/probe.npmrc"
+  NVM_PROBE_EXIT=0
+  nvm_npmrc_bad_news_bears "${TEST_DIR}/probe.npmrc" || NVM_PROBE_EXIT=$?
+  [ ! -e "${TEST_DIR}/grep-was-called" ] || exit 10
+  [ "${NVM_PROBE_EXIT}" = 0 ] || exit 11
+) || die 'nvm_npmrc_bad_news_bears must read npmrc files without calling nvm_grep'
+
 cleanup