[New] add nvm_has_italics, to detect terminal italics support via terminfo

nvm.sh

@@ -101,6 +101,11 @@ nvm_has_colors() {
   [ -t 1 ] && [ "${NVM_NUM_COLORS:--1}" -ge 8 ] && [ "${NVM_NO_COLORS-}" != '--no-colors' ]
 }
 
+# terminals without italics may render the italic escape as reverse video instead, so check terminfo's `sitm` capability
+nvm_has_italics() {
+  nvm_has_colors && command tput -T "${TERM:-vt100}" sitm >/dev/null 2>&1
+}
+
 nvm_curl_libz_support() {
   command curl -V 2>/dev/null | nvm_grep "^Features:" | nvm_grep -q "libz"
 }
@@ -5061,7 +5066,7 @@ nvm() {
         nvm_install_lock_name nvm_acquire_install_lock nvm_release_install_lock \
         nvm_list_aliases nvm_make_alias nvm_print_alias_file nvm_print_alias_path \
         nvm_print_default_alias nvm_print_formatted_alias nvm_resolve_local_alias \
-        nvm_sanitize_path nvm_has_colors nvm_process_parameters \
+        nvm_sanitize_path nvm_has_colors nvm_has_italics nvm_process_parameters \
         nvm_node_version_has_solaris_binary nvm_iojs_version_has_solaris_binary \
         nvm_curl_libz_support nvm_command_info nvm_is_zsh nvm_stdout_is_terminal \
         nvm_npmrc_bad_news_bears nvm_sanitize_auth_header \

test/fast/Unit tests/nvm_has_italics

@@ -0,0 +1,80 @@
+#!/bin/sh
+
+WORK="${PWD}/nvm-has-italics-work.$$"
+FAKE_BIN="${WORK}/bin"
+TPUT_LOG="${WORK}/tput.log"
+
+cleanup() {
+  command rm -rf "${WORK}"
+  unset -f cleanup die nvm_has_colors
+}
+die () { echo "$@" ; cleanup ; exit 1; }
+
+: nvm.sh
+\. ../../../nvm.sh
+
+nvm_has_colors() { return 0; }
+
+command mkdir -p "${FAKE_BIN}"
+command cat > "${FAKE_BIN}/tput" <<EOF
+#!/bin/sh
+echo "\$*" > "${TPUT_LOG}"
+command printf '\033[3m'
+exit "\${FAKE_TPUT_STATUS-0}"
+EOF
+command chmod +x "${FAKE_BIN}/tput"
+
+(
+  export PATH="${FAKE_BIN}:${PATH}" TERM=xterm-256color
+  nvm_has_italics
+) || die 'nvm_has_italics should be true when terminfo has the sitm capability'
+[ "$(command cat "${TPUT_LOG}")" = '-T xterm-256color sitm' ] \
+  || die "nvm_has_italics should query sitm for the current TERM; got >$(command cat "${TPUT_LOG}")<"
+
+OUTPUT="$(
+  export PATH="${FAKE_BIN}:${PATH}" TERM=xterm-256color
+  nvm_has_italics
+)"
+[ -z "${OUTPUT}" ] \
+  || die "nvm_has_italics should not print the escape sequence; got >${OUTPUT}<"
+
+(
+  export PATH="${FAKE_BIN}:${PATH}" TERM=screen FAKE_TPUT_STATUS=1
+  ! nvm_has_italics
+) || die 'nvm_has_italics should be false when terminfo lacks the sitm capability'
+
+(
+  export PATH="${FAKE_BIN}:${PATH}" TERM=not-a-terminal FAKE_TPUT_STATUS=3
+  ! nvm_has_italics
+) || die 'nvm_has_italics should be false when the terminal is unknown'
+
+(
+  export PATH="${FAKE_BIN}:${PATH}"
+  unset TERM
+  nvm_has_italics
+) || die 'nvm_has_italics should query vt100 when TERM is unset'
+[ "$(command cat "${TPUT_LOG}")" = '-T vt100 sitm' ] \
+  || die "nvm_has_italics should fall back to vt100 when TERM is unset; got >$(command cat "${TPUT_LOG}")<"
+
+(
+  PATH="${WORK}"
+  ! nvm_has_italics
+) || die 'nvm_has_italics should be false when tput is unavailable'
+
+command rm -f "${TPUT_LOG}"
+(
+  export PATH="${FAKE_BIN}:${PATH}" TERM=xterm-256color
+  nvm_has_colors() { return 1; }
+  ! nvm_has_italics
+) || die 'nvm_has_italics should be false when colors are disabled'
+[ ! -f "${TPUT_LOG}" ] \
+  || die 'nvm_has_italics should not query terminfo when colors are disabled'
+
+if nvm_has tput; then
+  (
+    export TERM=dumb
+    ! nvm_has_italics
+  ) || die 'nvm_has_italics should be false for the dumb terminal'
+fi
+
+cleanup