Fix an error for Style/WhereEquals when the second argument is not yet typed

changelog/fix_where_equals_error.md

@@ -0,0 +1 @@
+* [#1321](https://github.com/rubocop/rubocop-rails/pull/1321): Fix an error for `Rails/WhereEquals` when the second argument is not yet typed (`where("foo = ?", )`). ([@earlopain][])

lib/rubocop/cop/rails/where_equals.rb

@@ -44,10 +44,10 @@ def on_send(node)
 
             range = offense_range(node)
 
-            column_and_value = extract_column_and_value(template_node, value_node)
-            return unless column_and_value
+            column, value = extract_column_and_value(template_node, value_node)
+            return unless value
 
-            good_method = build_good_method(*column_and_value)
+            good_method = build_good_method(column, value)
             message = format(MSG, good_method: good_method)
 
             add_offense(range, message: message) do |corrector|
@@ -73,7 +73,7 @@ def extract_column_and_value(template_node, value_node)
           value =
             case template_node.value
             when EQ_ANONYMOUS_RE, IN_ANONYMOUS_RE
-              value_node.source
+              value_node&.source
             when EQ_NAMED_RE, IN_NAMED_RE
               return unless value_node&.hash_type?
 

spec/rubocop/cop/rails/where_equals_spec.rb

@@ -188,4 +188,16 @@
       User.where("id IN (#{sql})", name: 'Lastname').first
     RUBY
   end
+
+  it 'does not register an offense when using `=` and the second argument has no content' do
+    expect_no_offenses(<<~RUBY)
+      User.where('name = ?', )
+    RUBY
+  end
+
+  it 'does not register an offense when using `IN` and the second argument has no content' do
+    expect_no_offenses(<<~RUBY)
+      User.where("name IN (:names)", )
+    RUBY
+  end
 end