Fix CTE construction when passed arrays with more than 2 queries

Author: fatkodima

activerecord/lib/active_record/relation/query_methods.rb

@@ -1915,7 +1915,15 @@ def build_with_expression_from_value(value)
         when Arel::Nodes::SqlLiteral then Arel::Nodes::Grouping.new(value)
         when ActiveRecord::Relation then value.arel
         when Arel::SelectManager then value
-        when Array then value.map { |q| build_with_expression_from_value(q) }.reduce { |result, value| result.union(:all, value) }
+        when Array
+          parts = value.map do |query|
+            with_expression = build_with_expression_from_value(query)
+            with_expression.try(:ast) || with_expression
+          end
+
+          parts.reduce do |result, value|
+            Arel::Nodes::UnionAll.new(result, value)
+          end
         else
           raise ArgumentError, "Unsupported argument type: `#{value}` #{value.class}"
         end

activerecord/lib/arel/visitors/sqlite.rb

@@ -33,6 +33,31 @@ def visit_Arel_Nodes_IsDistinctFrom(o, collector)
           collector << " IS NOT "
           visit o.right, collector
         end
+
+        # Queries used in UNION should not be wrapped by parentheses,
+        # because it is an invalid syntax in SQLite.
+        def infix_value_with_paren(o, collector, value, suppress_parens = false)
+          collector << "( " unless suppress_parens
+
+          left = o.left.is_a?(Nodes::Grouping) ? o.left.expr : o.left
+          collector = if left.class == o.class
+            infix_value_with_paren(left, collector, value, true)
+          else
+            grouping_parentheses left, collector, false
+          end
+
+          collector << value
+
+          right = o.right.is_a?(Nodes::Grouping) ? o.right.expr : o.right
+          collector = if right.class == o.class
+            infix_value_with_paren(right, collector, value, true)
+          else
+            grouping_parentheses right, collector, false
+          end
+
+          collector << " )" unless suppress_parens
+          collector
+        end
     end
   end
 end

activerecord/test/cases/relation/with_test.rb

@@ -9,6 +9,7 @@ module ActiveRecord
   class WithTest < ActiveRecord::TestCase
     fixtures :comments, :posts, :companies
 
+    SPECIAL_POSTS = [2].freeze
     POSTS_WITH_TAGS = [1, 2, 7, 8, 9, 10, 11].freeze
     POSTS_WITH_COMMENTS = [1, 2, 4, 5, 7].freeze
     POSTS_WITH_MULTIPLE_COMMENTS = [1, 4, 5].freeze
@@ -63,13 +64,14 @@ def test_with_when_invalid_params_are_passed
 
       def test_with_when_passing_arrays
         relation = Post
-          .with(posts_with_tags_or_comments: [
-            Post.where("tags_count > 0"),
+          .with(posts_with_special_type_or_tags_or_comments: [
+            Post.where(type: "SpecialPost"),
+            Arel.sql("SELECT * FROM posts WHERE tags_count > 0"), # arel node on purpose
             Post.where("legacy_comments_count > 0")
           ])
-          .from("posts_with_tags_or_comments AS posts")
+          .from("posts_with_special_type_or_tags_or_comments AS posts")
 
-        assert_equal (POSTS_WITH_TAGS + POSTS_WITH_COMMENTS).sort, relation.order(:id).pluck(:id)
+        assert_equal (SPECIAL_POSTS + POSTS_WITH_TAGS + POSTS_WITH_COMMENTS).sort, relation.order(:id).pluck(:id)
       end
 
       def test_with_recursive