Robustify disambiguation of full/approximate matches.

Fixes #3942.


[SVN r59744]

Author: vprus

src/options_description.cpp

@@ -306,6 +306,7 @@ namespace boost { namespace program_options {
                                       bool short_ignore_case) const
     {
         shared_ptr<option_description> found;
+        bool had_full_match = false;
         vector<string> approximate_matches;
         vector<string> full_matches;
 
@@ -323,15 +324,17 @@ namespace boost { namespace program_options {
             if (r == option_description::full_match)
             {                
                 full_matches.push_back(m_options[i]->key(name));
+                found = m_options[i];
+                had_full_match = true;
             } 
             else 
             {                        
                 // FIXME: the use of 'key' here might not
                 // be the best approach.
                 approximate_matches.push_back(m_options[i]->key(name));
+                if (!had_full_match)
+                    found = m_options[i];
             }
-
-            found = m_options[i];
         }
         if (full_matches.size() > 1) 
             boost::throw_exception(

test/options_description_test.cpp

@@ -53,6 +53,17 @@ void test_approximation()
     BOOST_CHECK_EQUAL(desc.find("all", true).long_name(), "all");
     BOOST_CHECK_EQUAL(desc.find("all-ch", true).long_name(), "all-chroots");
 
+    options_description desc2;
+    desc2.add_options()
+        ("help", "display this message")
+        ("config", value<string>(), "config file name")
+        ("config-value", value<string>(), "single config value")
+        ;
+
+    BOOST_CHECK_EQUAL(desc2.find("config", true).long_name(), "config");
+    BOOST_CHECK_EQUAL(desc2.find("config-value", true).long_name(), 
+                      "config-value");
+
 
 //    BOOST_CHECK(desc.count_approx("foo") == 1);
 //    set<string> a = desc.approximations("f");