[patch] Bug 4177

[Vincent van Ravesteijn]

http://www.lyx.org/trac/ticket/4177
This patch ensures that only environment variable strings (i.e. strings 
that start with $) are replaced when the resolved environment variable 
is not an empty string.

Ok and does this also work at other platforms ?


Vincent
Index: src/support/filetools.cpp
===================================================================
--- src/support/filetools.cpp   (revision 28998)
+++ src/support/filetools.cpp   (working copy)
@@ -526,16 +526,23 @@
        static boost::regex envvar_br_re("(.*)" + envvar_br + "(.*)");
        static boost::regex envvar_re("(.*)" + envvar + "(.*)");
        boost::smatch what;
-
-       string result = path;
+       string result;
+       string remaining = path;
        while (1) {
-               regex_match(result, what, envvar_br_re);
+               regex_match(remaining, what, envvar_br_re);
                if (!what[0].matched) {
-                       regex_match(result, what, envvar_re);
-                       if (!what[0].matched)
+                       regex_match(remaining, what, envvar_re);
+                       if (!what[0].matched) {
+                               result += remaining;
                                break;
+                       }
                }
-               result = what.str(1) + getEnv(what.str(2)) + what.str(3);
+               string env_var = getEnv(what.str(2));
+               if (!env_var.empty())
+                       result += what.str(1) + env_var;
+               else
+                       result += what.str(1) + "$" + what.str(2);
+               remaining = what.str(3);
        }
        return result;
 }