refactor(builder): Be more explicit in how takes_values is used

Author: epage

clap_builder/src/builder/action.rs

@@ -1,6 +1,8 @@
 #[cfg(debug_assertions)]
 use crate::util::AnyValueId;
 
+use crate::builder::ValueRange;
+
 /// Behavior of arguments when they are encountered while parsing
 ///
 /// # Examples
@@ -369,6 +371,20 @@ impl ArgAction {
         }
     }
 
+    pub(crate) fn default_num_args(&self) -> ValueRange {
+        match self {
+            Self::Set => ValueRange::SINGLE,
+            Self::Append => ValueRange::SINGLE,
+            Self::SetTrue => ValueRange::EMPTY,
+            Self::SetFalse => ValueRange::EMPTY,
+            Self::Count => ValueRange::EMPTY,
+            Self::Help => ValueRange::EMPTY,
+            Self::HelpShort => ValueRange::EMPTY,
+            Self::HelpLong => ValueRange::EMPTY,
+            Self::Version => ValueRange::EMPTY,
+        }
+    }
+
     pub(crate) fn default_value(&self) -> Option<&'static std::ffi::OsStr> {
         match self {
             Self::Set => None,

clap_builder/src/builder/arg.rs

@@ -4546,11 +4546,7 @@ impl Arg {
         if val_names_len > 1 {
             self.num_vals.get_or_insert(val_names_len.into());
         } else {
-            let nargs = if self.get_action().takes_values() {
-                ValueRange::SINGLE
-            } else {
-                ValueRange::EMPTY
-            };
+            let nargs = self.get_action().default_num_args();
             self.num_vals.get_or_insert(nargs);
         }
     }