dotest.py: Fail if we detect multiple tests with the same name

[labath]

Summary

Log files produced by dotest have names derived from the test name, and this produces errors in
case we have multiple tests with the same name. Additionally, it's good if the test name explains
what the test is testing (which it clearly doesn't do well if there are multiple tests with
identical names). This commit makes the presence of such tests a hard error.

[tberghammer]

LGTM

lldb/trunk/test/dotest.py

 # Test results handling globals
 results_filename = None
 results_port = None
 results_file_object = None
 results_formatter_name = None
 results_formatter_object = None
 results_formatter_options = None
 
+# The names of all tests. Used to assert we don't have two tests with the same base name.
+all_tests = set()
+
 def usage(parser):
     parser.print_help()
     if verbose > 0:
         print """
 Examples:
 
 This is an example of using the -f option to pinpoint to a specific test class
 and test method to be run:

 def visit(prefix, dir, names):
     """Visitor function for os.path.walk(path, visit, arg)."""
 
     global suite
     global regexp
     global filters
     global fs4all
     global excluded
+    global all_tests
 
     if set(dir.split(os.sep)).intersection(excluded):
         #print "Detected an excluded dir component: %s" % dir
         return
 
     for name in names:
         if os.path.isdir(os.path.join(dir, name)):
             continue
 
         if '.py' == os.path.splitext(name)[1] and name.startswith(prefix):
+
+            if name in all_tests:
+                raise Exception("Found multiple tests with the name %s" % name)
+            all_tests.add(name)
+
             # Try to match the regexp pattern, if specified.
             if regexp:
                 import re
                 if re.search(regexp, name):
                     #print "Filename: '%s' matches pattern: '%s'" % (name, regexp)
                     pass
                 else:
                     #print "Filename: '%s' does not match pattern: '%s'" % (name, regexp)