Add Node#loc? to determine if a node has a given location

changelog/new_add_nodeloc_to_determine_if_a_node_has_a.md

@@ -0,0 +1 @@
+* [#346](https://github.com/rubocop/rubocop-ast/pull/346): Add `Node#loc?` to determine if a node has a given location. ([@dvandersluis][])

lib/rubocop/ast/node.rb

@@ -538,15 +538,20 @@ def guard_clause?
         node.match_guard_clause?
       end
 
+      # Shortcut to safely check if a location is present
+      # @return [Boolean]
+      def loc?(which_loc)
+        return false unless loc.respond_to?(which_loc)
+
+        !loc.public_send(which_loc).nil?
+      end
+
       # Shortcut to safely test a particular location, even if
       # this location does not exist or is `nil`
       def loc_is?(which_loc, str)
-        return false unless loc.respond_to?(which_loc)
-
-        location = loc.public_send(which_loc)
-        return false unless location
+        return false unless loc?(which_loc)
 
-        location.is?(str)
+        loc.public_send(which_loc).is?(str)
       end
 
       # @!method match_guard_clause?(node = self)

spec/rubocop/ast/node_spec.rb

@@ -1110,6 +1110,28 @@ class << expr
     end
   end
 
+  describe '#loc?' do
+    let(:src) { '%i[>> sym << sym2]' }
+
+    before(:all) { RSpec::Matchers.alias_matcher :have_loc, :be_loc }
+
+    context 'when loc exists' do
+      let(:src) { ':sym' }
+
+      it 'returns true when the location exists' do
+        expect(node).to have_loc(:begin)
+      end
+    end
+
+    it 'returns false when requested loc is `nil`' do
+      expect(node).not_to have_loc(:begin)
+    end
+
+    it 'returns false when requested loc does not exist' do
+      expect(node).not_to have_loc(:foo)
+    end
+  end
+
   describe '#loc_is?' do
     let(:src) { '%i[>> sym << sym2]' }