fix: fixes a bug that allowed options to pass parsing when no value w…

…as provided

Since options have `empty_values(true)` by default, so long as another valid flag
or option came after the option in question, clap would parse it as an empty value
incorrectly. This commit forces the user to explicitly add an empty value.

`--option "" --flag` is allowed
`--option --flag` is no longer allowed unless the user has *also* set `min_values(0)`

This commit also fixes an issue where `-o=` would be parsed as a value of `Some("=")`
instead of `Some("")`.

Closes #1105

src/app/validator.rs

@@ -139,7 +139,7 @@ impl<'a, 'b, 'z> Validator<'a, 'b, 'z> {
                 let mut c_with = find_from!($p, &$name, blacklist, &$matcher);
                 c_with = c_with.or(
                     $p.find_any_arg(&$name).map_or(None, |aa| aa.blacklist())
-                                           .map_or(None, 
+                                           .map_or(None,
                                                 |bl| bl.iter().find(|arg| $matcher.contains(arg)))
                                            .map_or(None, |an| $p.find_any_arg(an))
                                            .map_or(None, |aa| Some(format!("{}", aa)))
@@ -312,7 +312,8 @@ impl<'a, 'b, 'z> Validator<'a, 'b, 'z> {
             num == 0
         } else { false };
         // Issue 665 (https://github.com/kbknapp/clap-rs/issues/665)
-        if a.takes_value() && !(a.is_set(ArgSettings::EmptyValues) || min_vals_zero)  && ma.vals.is_empty() {
+        // Issue 1105 (https://github.com/kbknapp/clap-rs/issues/1105)
+        if a.takes_value() && !min_vals_zero && ma.vals.is_empty() {
             return Err(Error::empty_value(a,
                                           &*usage::create_error_usage(self.0, matcher, None),
                                           self.0.color()));
@@ -410,7 +411,7 @@ impl<'a, 'b, 'z> Validator<'a, 'b, 'z> {
                         }
                     })
                 })
-            }}; 
+            }};
         }
         if a.is_set(ArgSettings::RequiredUnlessAll) {
             check!(all, self.0, a, matcher)

src/osstringext.rs

@@ -56,11 +56,17 @@ impl OsStrExt2 for OsStr {
     }
 
     fn trim_left_matches(&self, byte: u8) -> &OsStr {
+        let mut found = false;
         for (i, b) in self.as_bytes().iter().enumerate() {
             if b != &byte {
                 return OsStr::from_bytes(&self.as_bytes()[i..]);
+            } else {
+                found = true;
             }
         }
+        if found {
+            return OsStr::from_bytes(&self.as_bytes()[self.len_()..]);
+        }
         &*self
     }