[Dexter] Mutually exclusive argument group for --builder and --binary

[StephenTozer]

Summary

Dexter currently accepts two possible arguments to determine the binary used for testing; either --builder <builder> (and optionally compiler/linker flags) to build the binary, or --binary <binary> to use the provided binary directly. If both are passed, then --binary overrides --builder; if neither are passed, then an error is raised. This patch instead puts these arguments into a required mutually exclusive argument group, so that an error is automatically raised by argparse if both or neither are given.

As an additional change, the --cflags and --ldflags will now raise a warning if they are passed without the --builder flag, as they are meaningless if Dexter is using a pre-built binary.

[Orlando]

LGTM

cross-project-tests/debuginfo-tests/dexter/dex/builder/ParserOptions.py

except AttributeError:
             results[os.path.splitext(f)[0]] = os.path.abspath(
                 os.path.join(scripts_directory, f))
 
         _find_build_scripts.cached = results
         return results
 
 
 def add_builder_tool_arguments(parser):
-    parser.add_argument('--binary',
+    build_group = parser.add_mutually_exclusive_group(required=True)
+    build_group.add_argument('--binary',
                              metavar="<file>",
-                        help='provide binary file to override --builder')
+                             help='provide binary file instead of --builder')
 
-    parser.add_argument(
+    build_group.add_argument(
         '--builder',
         type=str,
         choices=sorted(_find_build_scripts().keys()),
         help='test builder to use')
     parser.add_argument(
         '--cflags', type=str, default='', help='compiler flags')
     parser.add_argument('--ldflags', type=str, default='', help='linker flags')
 
 
 def handle_builder_tool_options(context: Context) -> str:
     return _find_build_scripts()[context.options.builder]

cross-project-tests/debuginfo-tests/dexter/dex/tools/TestToolBase.py

def add_tool_arguments(self, parser, defaults):
             default=os.path.abspath(
                 os.path.join(get_root_directory(), '..', 'results',
                              datetime.now().strftime('%Y-%m-%d-%H%M-%S'))),
             help='directory to save results')
 
     def handle_options(self, defaults):
         options = self.context.options
 
-        # We accept either or both of --binary and --builder.
-        if not options.binary and not options.builder:
-            raise Error('expected --builder or --binary')
+        if not options.builder and (options.cflags or options.ldflags):
+            warn(self.context, '--cflags and --ldflags will be ignored when not'
+                               ' using --builder')
 
-        # --binary overrides --builder
         if options.binary:
-            if options.builder:
-                warn(self.context, "overriding --builder with --binary\n")
-
             options.binary = os.path.abspath(options.binary)
             if not os.path.isfile(options.binary):
                 raise Error('<d>could not find binary file</> <r>"{}"</>'
                             .format(options.binary))
         else:
             try:
                 self.build_script = handle_builder_tool_options(self.context)
             except ToolArgumentError as e: