imp(validator): Case-insensitive required_if_eq when arg is case-insensitive

src/build/arg/mod.rs

@@ -1460,6 +1460,38 @@ impl<'help> Arg<'help> {
     /// // We did use --other=special so "cfg" had become required but was missing.
     /// assert!(res.is_err());
     /// assert_eq!(res.unwrap_err().kind, ErrorKind::MissingRequiredArgument);
+    ///
+    /// let res = App::new("prog")
+    ///     .arg(Arg::new("cfg")
+    ///         .takes_value(true)
+    ///         .required_if_eq("other", "special")
+    ///         .long("config"))
+    ///     .arg(Arg::new("other")
+    ///         .long("other")
+    ///         .takes_value(true))
+    ///     .try_get_matches_from(vec![
+    ///         "prog", "--other", "SPECIAL"
+    ///     ]);
+    ///
+    /// // By default, the comparison is case-sensitive, so "cfg" wasn't required
+    /// assert!(res.is_ok());
+    ///
+    /// let res = App::new("prog")
+    ///     .arg(Arg::new("cfg")
+    ///         .takes_value(true)
+    ///         .required_if_eq("other", "special")
+    ///         .long("config"))
+    ///     .arg(Arg::new("other")
+    ///         .long("other")
+    ///         .case_insensitive(true)
+    ///         .takes_value(true))
+    ///     .try_get_matches_from(vec![
+    ///         "prog", "--other", "SPECIAL"
+    ///     ]);
+    ///
+    /// // However, case-insensitive comparisons can be enabled.  This typically occurs when using Arg::possible_values().
+    /// assert!(res.is_err());
+    /// assert_eq!(res.unwrap_err().kind, ErrorKind::MissingRequiredArgument);
     /// ```
     /// [`Arg::requires(name)`]: Arg::requires()
     /// [Conflicting]: Arg::conflicts_with()
@@ -3700,8 +3732,15 @@ impl<'help> Arg<'help> {
         }
     }
 
-    /// When used with [`Arg::possible_values`] it allows the argument value to pass validation even
-    /// if the case differs from that of the specified `possible_value`.
+    /// When used with [`Arg::possible_values`] it allows the argument
+    /// value to pass validation even if the case differs from that of
+    /// the specified `possible_value`.
+    ///
+    /// When other arguments are conditionally required based on the
+    /// value of a case-insensitive argument, the equality check done
+    /// by [`Arg::required_if_eq`], [`Arg::required_if_eq_any`], or
+    /// [`Arg::required_if_eq_all`] is case-insensitive.
+    ///
     ///
     /// **NOTE:** Setting this requires [`ArgSettings::TakesValue`]
     ///

src/parse/arg_matcher.rs

@@ -117,10 +117,11 @@ impl ArgMatcher {
         self.0.args.iter()
     }
 
-    pub(crate) fn inc_occurrence_of(&mut self, arg: &Id) {
+    pub(crate) fn inc_occurrence_of(&mut self, arg: &Id, ci: bool) {
         debug!("ArgMatcher::inc_occurrence_of: arg={:?}", arg);
         let ma = self.entry(arg).or_insert(MatchedArg::new());
         ma.set_ty(ValueType::CommandLine);
+        ma.set_case_insensitive(ci);
         ma.occurs += 1;
     }
 

src/parse/matches/matched_arg.rs

@@ -22,6 +22,7 @@ pub(crate) struct MatchedArg {
     pub(crate) ty: ValueType,
     indices: Vec<usize>,
     vals: Vec<Vec<OsString>>,
+    case_insensitive: bool,
 }
 
 impl Default for MatchedArg {
@@ -37,6 +38,7 @@ impl MatchedArg {
             ty: ValueType::Unknown,
             indices: Vec::new(),
             vals: Vec::new(),
+            case_insensitive: false,
         }
     }
 
@@ -122,13 +124,25 @@ impl MatchedArg {
     }
 
     pub(crate) fn contains_val(&self, val: &str) -> bool {
-        self.vals_flatten()
-            .any(|v| OsString::as_os_str(v) == OsStr::new(val))
+        self.vals_flatten().any(|v| {
+            if self.case_insensitive {
+                // For rust v1.53.0 and above, can use
+                // OsString.eq_ignore_ascii_case
+                // (https://github.com/rust-lang/rust/pull/80193)
+                v.to_string_lossy().to_lowercase() == val.to_lowercase()
+            } else {
+                OsString::as_os_str(v) == OsStr::new(val)
+            }
+        })
     }
 
     pub(crate) fn set_ty(&mut self, ty: ValueType) {
         self.ty = ty;
     }
+
+    pub(crate) fn set_case_insensitive(&mut self, ci: bool) {
+        self.case_insensitive = ci;
+    }
 }
 
 #[cfg(test)]

src/parse/parser.rs

@@ -1521,10 +1521,10 @@ impl<'help, 'app> Parser<'help, 'app> {
 
     /// Increase occurrence of specific argument and the grouped arg it's in.
     fn inc_occurrence_of_arg(&self, matcher: &mut ArgMatcher, arg: &Arg<'help>) {
-        matcher.inc_occurrence_of(&arg.id);
+        matcher.inc_occurrence_of(&arg.id, arg.is_set(ArgSettings::IgnoreCase));
         // Increment or create the group "args"
         for group in self.app.groups_for_arg(&arg.id) {
-            matcher.inc_occurrence_of(&group);
+            matcher.inc_occurrence_of(&group, false);
         }
     }
 }

tests/require.rs

@@ -533,6 +533,47 @@ fn required_if_val_present_fail() {
     assert_eq!(res.unwrap_err().kind, ErrorKind::MissingRequiredArgument);
 }
 
+#[test]
+fn required_if_val_present_case_insensitive_pass() {
+    let res = App::new("ri")
+        .arg(
+            Arg::new("cfg")
+                .required_if_eq("extra", "Val")
+                .takes_value(true)
+                .long("config"),
+        )
+        .arg(
+            Arg::new("extra")
+                .takes_value(true)
+                .long("extra")
+                .case_insensitive(true),
+        )
+        .try_get_matches_from(vec!["ri", "--extra", "vaL", "--config", "my.cfg"]);
+
+    assert!(res.is_ok());
+}
+
+#[test]
+fn required_if_val_present_case_insensitive_fail() {
+    let res = App::new("ri")
+        .arg(
+            Arg::new("cfg")
+                .required_if_eq("extra", "Val")
+                .takes_value(true)
+                .long("config"),
+        )
+        .arg(
+            Arg::new("extra")
+                .takes_value(true)
+                .long("extra")
+                .case_insensitive(true),
+        )
+        .try_get_matches_from(vec!["ri", "--extra", "vaL"]);
+
+    assert!(res.is_err());
+    assert_eq!(res.unwrap_err().kind, ErrorKind::MissingRequiredArgument);
+}
+
 #[test]
 fn required_if_all_values_present_pass() {
     let res = App::new("ri")