From 2ae1403d5c57388edc4d587b1511804ef5413662 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Mon, 13 Dec 2021 01:26:06 +0900
Subject: [PATCH] Add `value_omission` method to `AST::PairNode`

Follow up to https://github.com/whitequark/parser/pull/818

This PR adds `value_omission` method to `AST::PairNode` for Ruby 3.1's
hash value omission.
It can replace string match with that named API.
---
 changelog/new_add_value_omission_to_pair_node.md |  1 +
 lib/rubocop/ast/node/pair_node.rb                |  7 +++++++
 spec/rubocop/ast/pair_node_spec.rb               | 14 ++++++++++++++
 3 files changed, 22 insertions(+)
 create mode 100644 changelog/new_add_value_omission_to_pair_node.md

diff --git a/changelog/new_add_value_omission_to_pair_node.md b/changelog/new_add_value_omission_to_pair_node.md
new file mode 100644
index 000000000..756d32a3d
--- /dev/null
+++ b/changelog/new_add_value_omission_to_pair_node.md
@@ -0,0 +1 @@
+* [#10219](https://github.com/rubocop/rubocop/pull/10219): Add `value_omission` method to `AST::PairNode` for Ruby 3.1's hash value omission. ([@koic][])
diff --git a/lib/rubocop/ast/node/pair_node.rb b/lib/rubocop/ast/node/pair_node.rb
index af65dfa12..4a04590d3 100644
--- a/lib/rubocop/ast/node/pair_node.rb
+++ b/lib/rubocop/ast/node/pair_node.rb
@@ -62,6 +62,13 @@ def inverse_delimiter(*deprecated, with_spacing: deprecated.first)
       def value_on_new_line?
         key.loc.line != value.loc.line
       end
+
+      # Checks whether the `pair` uses hash value omission.
+      #
+      # @return [Boolean] whether this `pair` uses hash value omission
+      def value_omission?
+        source.end_with?(':')
+      end
     end
   end
 end
diff --git a/spec/rubocop/ast/pair_node_spec.rb b/spec/rubocop/ast/pair_node_spec.rb
index 7168faa8b..ec2029a99 100644
--- a/spec/rubocop/ast/pair_node_spec.rb
+++ b/spec/rubocop/ast/pair_node_spec.rb
@@ -711,4 +711,18 @@
       end
     end
   end
+
+  describe '#value_omission?' do
+    context 'when using hash value omission', :ruby31 do
+      let(:source) { '{ x: }' }
+
+      it { expect(pair_node).to be_value_omission }
+    end
+
+    context 'when not using hash value omission' do
+      let(:source) { '{ x: x }' }
+
+      it { expect(pair_node).not_to be_value_omission }
+    end
+  end
 end