[Fix] install.sh: check mkdir return codes

If directory creation fails (e.g., permissions), the script would continue and fail with confusing errors later.
Fail early with a clear error message instead.

Bugs introduced in 68bf93514b, 6cee20a071, and 703babe60a.

install.sh

@@ -149,7 +149,10 @@ install_nvm_from_git() {
     fetch_error="Failed to fetch origin with $NVM_VERSION. Please report this!"
     nvm_echo "=> Downloading nvm from git to '$INSTALL_DIR'"
     command printf '\r=> '
-    mkdir -p "${INSTALL_DIR}"
+    mkdir -p "${INSTALL_DIR}" || {
+      nvm_echo >&2 "Failed to create directory '${INSTALL_DIR}'"
+      exit 2
+    }
     if [ "$(ls -A "${INSTALL_DIR}")" ]; then
       # Initializing repo
       command git init "${INSTALL_DIR}" || {
@@ -234,7 +237,10 @@ install_nvm_as_script() {
   NVM_BASH_COMPLETION_SOURCE="$(nvm_source script-nvm-bash-completion)"
 
   # Downloading to $INSTALL_DIR
-  mkdir -p "$INSTALL_DIR"
+  mkdir -p "$INSTALL_DIR" || {
+    nvm_echo >&2 "Failed to create directory '$INSTALL_DIR'"
+    return 1
+  }
   if [ -f "$INSTALL_DIR/nvm.sh" ]; then
     nvm_echo "=> nvm is already installed in $INSTALL_DIR, trying to update the script"
   else
@@ -374,7 +380,10 @@ nvm_do_install() {
     fi
 
     if [ "${NVM_DIR}" = "$(nvm_default_install_dir)" ]; then
-      mkdir "${NVM_DIR}"
+      mkdir "${NVM_DIR}" || {
+        nvm_echo >&2 "Failed to create directory '${NVM_DIR}'"
+        exit 2
+      }
     else
       nvm_echo >&2 "You have \$NVM_DIR set to \"${NVM_DIR}\", but that directory does not exist. Check your profile files and environment."
       exit 1

test/install_script/nvm_mkdir_error_handling

@@ -0,0 +1,49 @@
+#!/bin/sh
+
+cleanup () {
+  if [ -n "${SAVE_NVM_DIR-}" ]; then
+    NVM_DIR="$SAVE_NVM_DIR"
+  fi
+  unset -f die cleanup
+  unset SAVE_NVM_DIR
+}
+die () { echo "$@" ; cleanup ; exit 1; }
+
+SAVE_NVM_DIR="$NVM_DIR"
+
+NVM_ENV=testing \. ../../install.sh
+
+# install_nvm_from_git is available
+type install_nvm_from_git > /dev/null 2>&1 || die 'install_nvm_from_git is not available'
+
+# install_nvm_as_script is available
+type install_nvm_as_script > /dev/null 2>&1 || die 'install_nvm_as_script is not available'
+
+# nvm_do_install is available
+type nvm_do_install > /dev/null 2>&1 || die 'nvm_do_install is not available'
+
+IMPOSSIBLE_DIR="/dev/null/impossible_path"
+
+## install_nvm_from_git: mkdir failure should exit with code 2 and print error
+OUTPUT="$(NVM_DIR="${IMPOSSIBLE_DIR}" install_nvm_from_git 2>&1)"
+EXIT_CODE=$?
+[ "${EXIT_CODE}" = '2' ] || die "install_nvm_from_git should exit 2 on mkdir failure, got ${EXIT_CODE}"
+echo "${OUTPUT}" | grep -q "Failed to create directory" || die "install_nvm_from_git should print mkdir error message, got: ${OUTPUT}"
+
+## install_nvm_as_script: mkdir failure should return 1 and print error
+OUTPUT="$(NVM_DIR="${IMPOSSIBLE_DIR}" install_nvm_as_script 2>&1)"
+EXIT_CODE=$?
+[ "${EXIT_CODE}" = '1' ] || die "install_nvm_as_script should return 1 on mkdir failure, got ${EXIT_CODE}"
+echo "${OUTPUT}" | grep -q "Failed to create directory" || die "install_nvm_as_script should print mkdir error message, got: ${OUTPUT}"
+
+## nvm_do_install: mkdir failure for default dir should exit with code 2 and print error
+# Override nvm_default_install_dir to return the impossible path so the mkdir branch is taken
+nvm_default_install_dir() {
+  printf %s "${IMPOSSIBLE_DIR}"
+}
+OUTPUT="$(NVM_DIR="${IMPOSSIBLE_DIR}" nvm_do_install 2>&1)"
+EXIT_CODE=$?
+[ "${EXIT_CODE}" = '2' ] || die "nvm_do_install should exit 2 on mkdir failure, got ${EXIT_CODE}"
+echo "${OUTPUT}" | grep -q "Failed to create directory" || die "nvm_do_install should print mkdir error message, got: ${OUTPUT}"
+
+cleanup