fix: Don't panic when getting number of values

I was tempted to remove the exact-size nature.  Wouldn't be breaking
since it only panics but decided to go ahead and do this for now.

Fixes #3241

src/parse/matches/arg_matches.rs

@@ -260,6 +260,7 @@ impl ArgMatches {
  }
  let v = Values {
  iter: arg.vals_flatten().map(to_str_slice),
+ len: arg.num_vals(),
  };
  Some(v)
  }
@@ -274,6 +275,7 @@ impl ArgMatches {
  iter: arg
  .vals()
  .map(|g| g.iter().map(|x| x.to_str().expect(INVALID_UTF8)).collect()),
+ len: arg.vals().len(),
  };
  Some(v)
  }
@@ -376,6 +378,7 @@ impl ArgMatches {
  }
  let v = OsValues {
  iter: arg.vals_flatten().map(to_str_slice),
+ len: arg.num_vals(),
  };
  Some(v)
  }
@@ -863,6 +866,7 @@ impl ArgMatches {
  let arg = self.get_arg(&Id::from(id))?;
  let i = Indices {
  iter: arg.indices(),
+ len: arg.num_vals(),
  };
  Some(i)
  }
@@ -1080,6 +1084,7 @@ pub(crate) struct SubCommand {
 pub struct Values<'a> {
  #[allow(clippy::type_complexity)]
  iter: Map<Flatten<Iter<'a, Vec<OsString>>>, for<'r> fn(&'r OsString) -> &'r str>,
+ len: usize,
 }
 
 impl<'a> Iterator for Values<'a> {
@@ -1089,7 +1094,7 @@ impl<'a> Iterator for Values<'a> {
  self.iter.next()
  }
  fn size_hint(&self) -> (usize, Option<usize>) {
- self.iter.size_hint()
+ (self.len, Some(self.len))
  }
 }
 
@@ -1107,6 +1112,7 @@ impl<'a> Default for Values<'a> {
  static EMPTY: [Vec<OsString>; 0] = [];
  Values {
  iter: EMPTY[..].iter().flatten().map(|_| unreachable!()),
+ len: 0,
  }
  }
 }
@@ -1116,6 +1122,7 @@ impl<'a> Default for Values<'a> {
 pub struct GroupedValues<'a> {
  #[allow(clippy::type_complexity)]
  iter: Map<Iter<'a, Vec<OsString>>, fn(&Vec<OsString>) -> Vec<&str>>,
+ len: usize,
 }
 
 impl<'a> Iterator for GroupedValues<'a> {
@@ -1125,7 +1132,7 @@ impl<'a> Iterator for GroupedValues<'a> {
  self.iter.next()
  }
  fn size_hint(&self) -> (usize, Option<usize>) {
- self.iter.size_hint()
+ (self.len, Some(self.len))
  }
 }
 
@@ -1143,6 +1150,7 @@ impl<'a> Default for GroupedValues<'a> {
  static EMPTY: [Vec<OsString>; 0] = [];
  GroupedValues {
  iter: EMPTY[..].iter().map(|_| unreachable!()),
+ len: 0,
  }
  }
 }
@@ -1171,6 +1179,7 @@ impl<'a> Default for GroupedValues<'a> {
 pub struct OsValues<'a> {
  #[allow(clippy::type_complexity)]
  iter: Map<Flatten<Iter<'a, Vec<OsString>>>, fn(&OsString) -> &OsStr>,
+ len: usize,
 }
 
 impl<'a> Iterator for OsValues<'a> {
@@ -1180,7 +1189,7 @@ impl<'a> Iterator for OsValues<'a> {
  self.iter.next()
  }
  fn size_hint(&self) -> (usize, Option<usize>) {
- self.iter.size_hint()
+ (self.len, Some(self.len))
  }
 }
 
@@ -1198,6 +1207,7 @@ impl Default for OsValues<'_> {
  static EMPTY: [Vec<OsString>; 0] = [];
  OsValues {
  iter: EMPTY[..].iter().flatten().map(|_| unreachable!()),
+ len: 0,
  }
  }
 }
@@ -1226,6 +1236,7 @@ impl Default for OsValues<'_> {
 #[allow(missing_debug_implementations)]
 pub struct Indices<'a> {
  iter: Cloned<Iter<'a, usize>>,
+ len: usize,
 }
 
 impl<'a> Iterator for Indices<'a> {
@@ -1235,7 +1246,7 @@ impl<'a> Iterator for Indices<'a> {
  self.iter.next()
  }
  fn size_hint(&self) -> (usize, Option<usize>) {
- self.iter.size_hint()
+ (self.len, Some(self.len))
  }
 }
 
@@ -1254,6 +1265,7 @@ impl<'a> Default for Indices<'a> {
  // This is never called because the iterator is empty:
  Indices {
  iter: EMPTY[..].iter().cloned(),
+ len: 0,
  }
  }
 }
@@ -1320,4 +1332,56 @@ mod tests {
  let mut indices = matches.indices_of("").unwrap_or_default();
  assert_eq!(indices.next(), None);
  }
+
+ #[test]
+ fn values_exact_size() {
+ let l = crate::App::new("test")
+ .arg(
+ crate::Arg::new("POTATO")
+ .takes_value(true)
+ .multiple_values(true)
+ .required(true),
+ )
+ .try_get_matches_from(["test", "one"])
+ .unwrap()
+ .values_of("POTATO")
+ .expect("present")
+ .len();
+ assert_eq!(l, 1);
+ }
+
+ #[test]
+ fn os_values_exact_size() {
+ let l = crate::App::new("test")
+ .arg(
+ crate::Arg::new("POTATO")
+ .takes_value(true)
+ .multiple_values(true)
+ .allow_invalid_utf8(true)
+ .required(true),
+ )
+ .try_get_matches_from(["test", "one"])
+ .unwrap()
+ .values_of_os("POTATO")
+ .expect("present")
+ .len();
+ assert_eq!(l, 1);
+ }
+
+ #[test]
+ fn indices_exact_size() {
+ let l = crate::App::new("test")
+ .arg(
+ crate::Arg::new("POTATO")
+ .takes_value(true)
+ .multiple_values(true)
+ .required(true),
+ )
+ .try_get_matches_from(["test", "one"])
+ .unwrap()
+ .indices_of("POTATO")
+ .expect("present")
+ .len();
+ assert_eq!(l, 1);
+ }
 }