Merge branch 'select-from-union' into 'master'

Replace direct use of Gitlab::SQL::Union with a "from_union" method

Closes #51307

See merge request gitlab-org/gitlab-ce!21672

2 files changed, 65 insertions, 0 deletions

diff --git a/spec/models/concerns/from_union_spec.rb b/spec/models/concerns/from_union_spec.rb
new file mode 100644
index 00000000000..ee427a667c6
--- /dev/null
+++ b/spec/models/concerns/from_union_spec.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe FromUnion do
+  describe '.from_union' do
+    let(:model) do
+      Class.new(ActiveRecord::Base) do
+        self.table_name = 'users'
+
+        include FromUnion
+      end
+    end
+
+    it 'selects from the results of the UNION' do
+      query = model.from_union([model.where(id: 1), model.where(id: 2)])
+
+      expect(query.to_sql).to match(/FROM \(SELECT.+UNION.+SELECT.+\) users/m)
+    end
+
+    it 'supports the use of a custom alias for the sub query' do
+      query = model.from_union(
+        [model.where(id: 1), model.where(id: 2)],
+        alias_as: 'kittens'
+      )
+
+      expect(query.to_sql).to match(/FROM \(SELECT.+UNION.+SELECT.+\) kittens/m)
+    end
+
+    it 'supports keeping duplicate rows' do
+      query = model.from_union(
+        [model.where(id: 1), model.where(id: 2)],
+        remove_duplicates: false
+      )
+
+      expect(query.to_sql)
+        .to match(/FROM \(SELECT.+UNION ALL.+SELECT.+\) users/m)
+    end
+  end
+end
diff --git a/spec/rubocop/cop/gitlab/union_spec.rb b/spec/rubocop/cop/gitlab/union_spec.rb
new file mode 100644
index 00000000000..5b06f30b25f
--- /dev/null
+++ b/spec/rubocop/cop/gitlab/union_spec.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'rubocop'
+require 'rubocop/rspec/support'
+require_relative '../../../../rubocop/cop/gitlab/union'
+
+describe RuboCop::Cop::Gitlab::Union do
+  include CopHelper
+
+  subject(:cop) { described_class.new }
+
+  it 'flags the use of Gitlab::SQL::Union.new' do
+    expect_offense(<<~SOURCE)
+    Gitlab::SQL::Union.new([foo])
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use the `FromUnion` concern, instead of using `Gitlab::SQL::Union` directly
+    SOURCE
+  end
+
+  it 'does not flag the use of Gitlab::SQL::Union in a spec' do
+    allow(cop).to receive(:in_spec?).and_return(true)
+
+    expect_no_offenses('Gitlab::SQL::Union.new([foo])')
+  end
+end