Minor cleanup/tuning.

The motivaiton was trying to make finding keyword handlers a bit
faster to address #4659. Didn't seem to have any measurable effect,
but I consider this code better anyway.

src/robot/libraries/BuiltIn.py

@@ -1865,23 +1865,20 @@ def run_keyword(self, name, *args):
         can be a variable and thus set dynamically, e.g. from a return value of
         another keyword or from the command line.
         """
-        ctx = self._context
-        if (is_string(name)
-                and not ctx.dry_run
-                and not self._accepts_embedded_arguments(name)):
-            name, args = self._replace_variables_in_name([name] + list(args))
         if not is_string(name):
             raise RuntimeError('Keyword name must be a string.')
+        ctx = self._context
+        if not (ctx.dry_run or self._accepts_embedded_arguments(name, ctx)):
+            name, args = self._replace_variables_in_name([name] + list(args))
         parent = ctx.steps[-1] if ctx.steps else (ctx.test or ctx.suite)
         kw = Keyword(name, args=args, parent=parent,
                      lineno=getattr(parent, 'lineno', None))
         return kw.run(ctx)
 
-    def _accepts_embedded_arguments(self, name):
+    def _accepts_embedded_arguments(self, name, ctx):
         if '{' in name:
-            runner = self._context.get_runner(name)
-            if hasattr(runner, 'embedded_args'):
-                return True
+            runner = ctx.get_runner(name)
+            return runner and hasattr(runner, 'embedded_args')
         return False
 
     def _replace_variables_in_name(self, name_and_args):
@@ -1890,6 +1887,8 @@ def _replace_variables_in_name(self, name_and_args):
         if not resolved:
             raise DataError(f'Keyword name missing: Given arguments {name_and_args} '
                             f'resolved to an empty list.')
+        if not is_string(resolved[0]):
+            raise RuntimeError('Keyword name must be a string.')
         return resolved[0], resolved[1:]
 
     @run_keyword_variant(resolve=0, dry_run=True)

src/robot/running/handlerstore.py

@@ -47,6 +47,8 @@ def __len__(self):
     def __contains__(self, name):
         if name in self._normal:
             return True
+        if not self._embedded:
+            return False
         return any(template.matches(name) for template in self._embedded)
 
     def __getitem__(self, name):

src/robot/running/namespace.py

@@ -311,10 +311,8 @@ def _get_bdd_style_runner(self, name, prefixes):
         return None
 
     def _get_implicit_runner(self, name):
-        runner = self._get_runner_from_resource_files(name)
-        if not runner:
-            runner = self._get_runner_from_libraries(name)
-        return runner
+        return (self._get_runner_from_resource_files(name) or
+                self._get_runner_from_libraries(name))
 
     def _get_runner_from_suite_file(self, name):
         if name not in self.user_keywords.handlers:
@@ -377,8 +375,8 @@ def _get_runner_from_resource_files(self, name):
                 handlers = self._select_best_matches(handlers)
                 if len(handlers) > 1:
                     handlers = self._filter_based_on_search_order(handlers)
-        if len(handlers) != 1:
-            self._raise_multiple_keywords_found(handlers, name)
+                    if len(handlers) > 1:
+                        self._raise_multiple_keywords_found(handlers, name)
         return handlers[0].create_runner(name, self.languages)
 
     def _get_runner_from_libraries(self, name):
@@ -393,8 +391,8 @@ def _get_runner_from_libraries(self, name):
                 handlers = self._filter_based_on_search_order(handlers)
                 if len(handlers) > 1:
                     handlers, pre_run_message = self._filter_stdlib_handler(handlers)
-        if len(handlers) != 1:
-            self._raise_multiple_keywords_found(handlers, name)
+                    if len(handlers) > 1:
+                        self._raise_multiple_keywords_found(handlers, name)
         runner = handlers[0].create_runner(name, self.languages)
         if pre_run_message:
             runner.pre_run_messages += (pre_run_message,)
@@ -447,11 +445,12 @@ def _custom_and_standard_keyword_conflict_warning(self, custom, standard):
         )
 
     def _get_explicit_runner(self, name):
-        handlers_and_names = [
-            (handler, kw_name)
-            for owner_name, kw_name in self._yield_owner_and_kw_names(name)
-            for handler in self._yield_handlers(owner_name, kw_name)
-        ]
+        handlers_and_names = []
+        for owner_name, kw_name in self._get_owner_and_kw_names(name):
+            for owner in chain(self.libraries.values(), self.resources.values()):
+                if eq(owner.name, owner_name) and kw_name in owner.handlers:
+                    for handler in owner.handlers.get_handlers(kw_name):
+                        handlers_and_names.append((handler, kw_name))
         if not handlers_and_names:
             return None
         if len(handlers_and_names) == 1:
@@ -464,15 +463,10 @@ def _get_explicit_runner(self, name):
             handler, kw_name = handlers_and_names[handlers.index(matches[0])]
         return handler.create_runner(kw_name, self.languages)
 
-    def _yield_owner_and_kw_names(self, full_name):
+    def _get_owner_and_kw_names(self, full_name):
         tokens = full_name.split('.')
-        for i in range(1, len(tokens)):
-            yield '.'.join(tokens[:i]), '.'.join(tokens[i:])
-
-    def _yield_handlers(self, owner_name, name):
-        for owner in chain(self.libraries.values(), self.resources.values()):
-            if eq(owner.name, owner_name) and name in owner.handlers:
-                yield from owner.handlers.get_handlers(name)
+        return [('.'.join(tokens[:index]), '.'.join(tokens[index:]))
+                for index in range(1, len(tokens))]
 
     def _raise_multiple_keywords_found(self, handlers, name, implicit=True):
         if any(hand.supports_embedded_args for hand in handlers):