fix(zsh): Use _default as zsh completion fallback

That is for a ValueHint of Unknown. This is consistent with bash where
compgen -f is used in such cases. In long experience with completions
distributed with zsh, the worst thing you can do is break filename
completion as that's the minimum most user's expect.

clap_complete/src/aot/shells/zsh.rs

@@ -396,10 +396,8 @@ fn value_completion(arg: &Arg) -> Option<String> {
         // NB! If you change this, please also update the table in `ValueHint` documentation.
         Some(
             match arg.get_value_hint() {
-                ValueHint::Unknown => {
-                    return None;
-                }
-                ValueHint::Other => "( )",
+                ValueHint::Unknown => "_default",
+                ValueHint::Other => "",
                 ValueHint::AnyPath => "_files",
                 ValueHint::FilePath => "_files",
                 ValueHint::DirPath => "_files -/",

clap_complete/tests/snapshots/aliases.zsh

@@ -15,10 +15,10 @@ _my-app() {
 
     local context curcontext="$curcontext" state line
     _arguments "${_arguments_options[@]}" : \
-'-o+[cmd option]: : ' \
-'-O+[cmd option]: : ' \
-'--option=[cmd option]: : ' \
-'--opt=[cmd option]: : ' \
+'-o+[cmd option]: :_default' \
+'-O+[cmd option]: :_default' \
+'--option=[cmd option]: :_default' \
+'--opt=[cmd option]: :_default' \
 '-f[cmd flag]' \
 '-F[cmd flag]' \
 '--flag[cmd flag]' \
@@ -27,7 +27,7 @@ _my-app() {
 '--help[Print help]' \
 '-V[Print version]' \
 '--version[Print version]' \
-'::positional:' \
+'::positional:_default' \
 && ret=0
 }
 

clap_complete/tests/snapshots/feature_sample.zsh

@@ -36,7 +36,7 @@ _my-app() {
         case $line[3] in
             (test)
 _arguments "${_arguments_options[@]}" : \
-'--case=[the case to test]: : ' \
+'--case=[the case to test]: :_default' \
 '-h[Print help]' \
 '--help[Print help]' \
 '-V[Print version]' \

clap_complete/tests/snapshots/home/static/exhaustive/zsh/zsh/_exhaustive

@@ -32,7 +32,7 @@ _exhaustive() {
         case $line[1] in
             (action)
 _arguments "${_arguments_options[@]}" : \
-'--set=[value]: : ' \
+'--set=[value]: :_default' \
 '--choice=[enum]: :(first second)' \
 '--set-true[bool]' \
 '*--count[number]' \
@@ -187,15 +187,15 @@ esac
 ;;
 (value)
 _arguments "${_arguments_options[@]}" : \
-'--delim=[]: : ' \
-'--tuple=[]: : : : ' \
-'--require-eq=[]: : ' \
+'--delim=[]: :_default' \
+'--tuple=[]: :_default: :_default' \
+'--require-eq=[]: :_default' \
 '--global[everywhere]' \
 '-h[Print help]' \
 '--help[Print help]' \
 '-V[Print version]' \
 '--version[Print version]' \
-'*;::term:' \
+'*;::term:_default' \
 && ret=0
 ;;
 (pacman)
@@ -272,16 +272,16 @@ _arguments "${_arguments_options[@]}" : \
 '--help[Print help]' \
 '-V[Print version]' \
 '--version[Print version]' \
-'::first:' \
-'::free:' \
+'::first:_default' \
+'::free:_default' \
 && ret=0
 ;;
 (alias)
 _arguments "${_arguments_options[@]}" : \
-'-o+[cmd option]: : ' \
-'-O+[cmd option]: : ' \
-'--option=[cmd option]: : ' \
-'--opt=[cmd option]: : ' \
+'-o+[cmd option]: :_default' \
+'-O+[cmd option]: :_default' \
+'--option=[cmd option]: :_default' \
+'--opt=[cmd option]: :_default' \
 '-f[cmd flag]' \
 '-F[cmd flag]' \
 '--flag[cmd flag]' \
@@ -291,14 +291,14 @@ _arguments "${_arguments_options[@]}" : \
 '--help[Print help]' \
 '-V[Print version]' \
 '--version[Print version]' \
-'::positional:' \
+'::positional:_default' \
 && ret=0
 ;;
 (hint)
 _arguments "${_arguments_options[@]}" : \
 '--choice=[]: :(bash fish zsh)' \
-'--unknown=[]: : ' \
-'--other=[]: :( )' \
+'--unknown=[]: :_default' \
+'--other=[]: :' \
 '-p+[]: :_files' \
 '--path=[]: :_files' \
 '-f+[]: :_files' \

clap_complete/tests/snapshots/special_commands.zsh

@@ -36,7 +36,7 @@ _my-app() {
         case $line[3] in
             (test)
 _arguments "${_arguments_options[@]}" : \
-'--case=[the case to test]: : ' \
+'--case=[the case to test]: :_default' \
 '-h[Print help]' \
 '--help[Print help]' \
 '-V[Print version]' \
@@ -45,12 +45,12 @@ _arguments "${_arguments_options[@]}" : \
 ;;
 (some_cmd)
 _arguments "${_arguments_options[@]}" : \
-'--config=[the other case to test]: : ' \
+'--config=[the other case to test]: :_default' \
 '-h[Print help]' \
 '--help[Print help]' \
 '-V[Print version]' \
 '--version[Print version]' \
-'*::path:' \
+'*::path:_default' \
 && ret=0
 ;;
 (some-cmd-with-hyphens)

clap_complete/tests/snapshots/sub_subcommands.zsh

@@ -36,7 +36,7 @@ _my-app() {
         case $line[3] in
             (test)
 _arguments "${_arguments_options[@]}" : \
-'--case=[the case to test]: : ' \
+'--case=[the case to test]: :_default' \
 '-h[Print help]' \
 '--help[Print help]' \
 '-V[Print version]' \

clap_complete/tests/snapshots/subcommand_last.zsh

@@ -17,7 +17,7 @@ _my-app() {
     _arguments "${_arguments_options[@]}" : \
 '-h[Print help]' \
 '--help[Print help]' \
-'::free:' \
+'::free:_default' \
 ":: :_my-app_commands" \
 "*::: :->my-app" \
 && ret=0

clap_complete/tests/snapshots/two_multi_valued_arguments.zsh

@@ -17,7 +17,7 @@ _my-app() {
     _arguments "${_arguments_options[@]}" : \
 '-h[Print help]' \
 '--help[Print help]' \
-'*::first -- first multi-valued argument:' \
+'*::first -- first multi-valued argument:_default' \
 && ret=0
 }
 

clap_complete/tests/snapshots/value_hint.zsh

@@ -16,8 +16,8 @@ _my-app() {
     local context curcontext="$curcontext" state line
     _arguments "${_arguments_options[@]}" : \
 '--choice=[]: :(bash fish zsh)' \
-'--unknown=[]: : ' \
-'--other=[]: :( )' \
+'--unknown=[]: :_default' \
+'--other=[]: :' \
 '-p+[]: :_files' \
 '--path=[]: :_files' \
 '-f+[]: :_files' \

clap_complete/tests/snapshots/value_terminator.zsh

@@ -17,7 +17,7 @@ _my-app() {
     _arguments "${_arguments_options[@]}" : \
 '-h[Print help]' \
 '--help[Print help]' \
-'*;::arguments -- multi-valued argument with a value terminator:' \
+'*;::arguments -- multi-valued argument with a value terminator:_default' \
 && ret=0
 }