Added tests and fixed display of conflicted flags

src/parse/validator.rs

@@ -170,14 +170,14 @@ impl<'b, 'c, 'z> Validator<'b, 'c, 'z> {
     fn build_conflict_err(&self, name: Id, matcher: &ArgMatcher) -> ClapResult<()> {
         debugln!("build_err!: name={}", name);
         let usg = Usage::new(self.p).create_usage_with_title(&[]);
-        if self.p.app.find(name).is_some() {
+        if let Some(other_arg) = self.p.app.find(name) {
             for &k in matcher.arg_names() {
                 if let Some(a) = self.p.app.find(k) {
                     if let Some(ref v) = a.blacklist {
                         if v.contains(&name) {
                             return Err(Error::argument_conflict(
                                 a,
-                                Some(name.to_string()),
+                                Some(other_arg.to_string()),
                                 &*usg,
                                 self.p.app.color(),
                             ));

tests/arg_conflicts.rs

@@ -0,0 +1,52 @@
+use clap::{App, Arg};
+
+#[test]
+fn two_conflicting_arguments() {
+    let a = App::new("two_conflicting_arguments")
+        .arg(
+            Arg::with_name("develop")
+                .long("develop")
+                .conflicts_with("production"),
+        )
+        .arg(
+            Arg::with_name("production")
+                .long("production")
+                .conflicts_with("develop"),
+        )
+        .try_get_matches_from(vec!["", "--develop", "--production"]);
+
+    assert!(a.is_err());
+    let a = a.unwrap_err();
+    assert_eq!(
+        a.cause,
+        "The argument \'--develop\' cannot be used with \'--production\'"
+    );
+}
+
+#[test]
+fn three_conflicting_arguments() {
+    let a = App::new("two_conflicting_arguments")
+        .arg(
+            Arg::with_name("one")
+                .long("one")
+                .conflicts_with_all(&["two", "three"]),
+        )
+        .arg(
+            Arg::with_name("two")
+                .long("two")
+                .conflicts_with_all(&["one", "three"]),
+        )
+        .arg(
+            Arg::with_name("three")
+                .long("three")
+                .conflicts_with_all(&["one", "two"]),
+        )
+        .try_get_matches_from(vec!["", "--one", "--two", "--three"]);
+
+    assert!(a.is_err());
+    let a = a.unwrap_err();
+    assert_eq!(
+        a.cause,
+        "The argument \'--one\' cannot be used with \'--two\'"
+    );
+}