[Ruby] Fix remove of prefix from method name

The prefix is now only removed at the start.

Fixes https://sourceforge.net/p/swig/bugs/1136/

CHANGES.current

@@ -7,6 +7,10 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
 Version 4.1.0 (in progress)
 ===========================
 
+2022-02-02: olly
+	    [Ruby] https://sourceforge.net/p/swig/bugs/1136/ Fix remove of prefix
+	    from method name to only remove it at the start.
+
 2022-02-01: olly
 	    #231 Handle returning an object by reference in a C++ trailing
 	    return type.

Examples/test-suite/ruby/ruby_naming_bugs_runme.rb

@@ -0,0 +1,16 @@
+#!/usr/bin/env ruby
+#
+# Regression tests for Ruby naming bugs
+#
+
+require 'swig_assert'
+
+require 'ruby_naming_bugs'
+
+# Prior to SWIG 4.1.0 the "Cool_" here was overzealously removed
+# while trying to remove a class name prefix, so this method would be
+# named "somethingFast" in Ruby instead.
+c = Ruby_naming_bugs::Cool.new()
+if c.somethingCool_Fast != 42
+  raise RuntimeError, "Incorrect value for somethingCool_Fast"
+end

Examples/test-suite/ruby_naming_bugs.i

@@ -0,0 +1,9 @@
+%module ruby_naming_bugs
+
+%inline %{
+  // Prior to SWIG 4.1.0 the "Cool_" here was overzealously removed while
+  // trying to remove a class name prefix.
+  struct Cool {
+    int somethingCool_Fast() { return 42; }
+  };
+%}

Source/Modules/ruby.cxx

@@ -106,9 +106,10 @@ public:
 
   char *strip(const_String_or_char_ptr s) {
     Clear(temp);
-    Append(temp, s);
     if (Strncmp(s, prefix, Len(prefix)) == 0) {
-      Replaceall(temp, prefix, "");
+      Append(temp, Char(s) + Len(prefix));
+    } else {
+      Append(temp, s);
     }
     return Char(temp);
   }