From bfabdbc278bb89b29c7d0a94c5a032ef00bbb110 Mon Sep 17 00:00:00 2001
From: maliv2 <259173856+maliv2@users.noreply.github.com>
Date: Wed, 14 Oct 2026 20:53:08 +0300
Subject: [PATCH] [Fix] `nvm use`: do not pile up `PATH` entries in nested
 sessions

`nvm_change_path` prepends the new version
(instead of replacing the existing nvm path)
when a system bin dir precedes an nvm path,
to handle macOS `path_helper` reordering the `PATH` of nested sessions
(#1652). However, the check matched a system dir followed by *any* nvm path.
Once a stale nvm path sits after the system dirs
(e.g. inherited by a nested shell, tmux, or an editor's terminal),
the check stays true forever,
so every `nvm use` prepends yet another entry and the previously used version is never removed from the `PATH`.

Only consider the first nvm path:
if it is not preceded by a system bin dir,
replace it in place as usual.

Fixes #3561
---
 nvm.sh                               |  9 +++++----
 test/fast/Unit tests/nvm_change_path | 13 +++++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/nvm.sh b/nvm.sh
index 990506ed..2d503d7a 100755
--- a/nvm.sh
+++ b/nvm.sh
@@ -1556,11 +1556,12 @@ nvm_change_path() {
     && ! nvm_echo "${1-}" | nvm_grep -Eq "${NVM_DIR_RE}/versions/[^/]*/[^/]*${2-}"; then
     nvm_echo "${3-}${2-}:${1-}"
   # if the initial path contains BOTH an nvm path (checked for above) and
-  # that nvm path is preceded by a system binary path, just prepend the
-  # supplementary path instead of replacing it.
+  # the first nvm path is preceded by a system binary path, just prepend the
+  # supplementary path instead of replacing it. Only what precedes the first
+  # nvm path counts, so that a shadowed nvm path further on does not make
+  # every change prepend yet another entry.
   # https://github.com/nvm-sh/nvm/issues/1652#issuecomment-342571223
-  elif nvm_echo "${1-}" | nvm_grep -Eq "(^|:)(/usr(/local)?)?${2-}:.*${NVM_DIR_RE}/[^/]*${2-}" \
-    || nvm_echo "${1-}" | nvm_grep -Eq "(^|:)(/usr(/local)?)?${2-}:.*${NVM_DIR_RE}/versions/[^/]*/[^/]*${2-}"; then
+  elif nvm_echo "${1%%"${NVM_DIR}"/*}" | nvm_grep -Eq "(^|:)(/usr(/local)?)?${2-}:"; then
     nvm_echo "${3-}${2-}:${1-}"
   # use sed to replace the existing nvm path with the supplementary path. This
   # preserves the order of the path.
diff --git a/test/fast/Unit tests/nvm_change_path b/test/fast/Unit tests/nvm_change_path
index b690b6df..4871b6c6 100755
--- a/test/fast/Unit tests/nvm_change_path	
+++ b/test/fast/Unit tests/nvm_change_path	
@@ -70,3 +70,16 @@ NEW_PATH=`nvm_change_path "$MAC_OS_NESTED_SESSION_PATH" "/bin" "$NVM_DIR/version
 NEW_PATH=`nvm_change_path "$MAC_OS_NESTED_SESSION_PATH" "/bin" "$NVM_DIR/v0.1.2"`
 
 [ "$NEW_PATH" = "$NVM_DIR/v0.1.2/bin:/usr/bin:/usr/local/bin:$NVM_DIR/versions/node/v4.5.0/bin" ] || die "Not correctly changed: $NEW_PATH "
+
+# an nvm path that was already prepended ahead of the system paths is replaced,
+# rather than piling up another entry on every change
+# https://github.com/nvm-sh/nvm/issues/3561
+PREPENDED_NESTED_SESSION_PATH=$NVM_DIR/versions/node/v7.1.0/bin:/usr/bin:/usr/local/bin:$NVM_DIR/versions/node/v4.5.0/bin
+
+NEW_PATH=`nvm_change_path "$PREPENDED_NESTED_SESSION_PATH" "/bin" "$NVM_DIR/versions/node/v8.0.0"`
+
+[ "$NEW_PATH" = "$NVM_DIR/versions/node/v8.0.0/bin:/usr/bin:/usr/local/bin:$NVM_DIR/versions/node/v4.5.0/bin" ] || die "Not correctly changed: $NEW_PATH "
+
+NEW_PATH=`nvm_change_path "$PREPENDED_NESTED_SESSION_PATH" "/bin" "$NVM_DIR/v0.1.2"`
+
+[ "$NEW_PATH" = "$NVM_DIR/v0.1.2/bin:/usr/bin:/usr/local/bin:$NVM_DIR/versions/node/v4.5.0/bin" ] || die "Not correctly changed: $NEW_PATH "