Fix crash on an endless method with empty parentheses

Formatting "def foo() = 1" raised Rufo::Bug. The empty-parameters branch
of visit_def_from_name wrote "()" but, unlike the other two branches, did
not skip the space after the closing parenthesis. The endless-method
check (current_token_kind == :on_op) therefore saw the space instead of
"=", skipped format_endless_method, and visiting the body then hit the
unconsumed " = 1".

Skip the space after "()" like the sibling branches do.

Fixes #361

Author: youdie006

lib/rufo/formatter.rb

@@ -2015,6 +2015,9 @@ def visit_def_from_name(name, params, body)
         check :on_rparen
         next_token
         write "()"
+        # Consume the space after `)` like the other branches do, so an endless
+        # method body (`def foo() = 1`) is detected below instead of crashing.
+        skip_space
       else
         write "("
 

spec/lib/rufo/formatter_source_specs/endless_methods.rb.spec

@@ -15,3 +15,15 @@ def foo = puts(    "a")
 
 #~# EXPECTED
 def foo = puts("a")
+
+#~# ORIGINAL format_endless_method_with_empty_params
+def foo() = 1
+
+#~# EXPECTED
+def foo() = 1
+
+#~# ORIGINAL format_endless_method_with_empty_params_and_spacing
+def foo()   =    1
+
+#~# EXPECTED
+def foo() = 1