Style/ExplicitBlockArgument: do not assume the block parameter name

The autocorector would generate invalid code if the old code
already defined the block parameter with any other name than `&block`.

changelog/fix_hardcoded_block_parameter_name.md

@@ -0,0 +1 @@
+* [#10064](https://github.com/rubocop/rubocop/pull/10064): Fix `Style/ExplicitBlockArgument` corrector assuming any existing block argument was named `block`. ([@byroot][])

lib/rubocop/cop/style/explicit_block_argument.rb

@@ -67,17 +67,27 @@ def on_yield(node)
             # so this can cause crashes in haml_lint
             return unless def_node
 
+            block_name = extract_block_name(def_node)
+
             add_offense(block_node) do |corrector|
               corrector.remove(block_body_range(block_node, send_node))
 
-              add_block_argument(send_node, corrector)
-              add_block_argument(def_node, corrector) if @def_nodes.add?(def_node)
+              add_block_argument(send_node, corrector, block_name)
+              add_block_argument(def_node, corrector, block_name) if @def_nodes.add?(def_node)
             end
           end
         end
 
         private
 
+        def extract_block_name(def_node)
+          if def_node.block_argument?
+            def_node.arguments.last.name
+          else
+            'block'
+          end
+        end
+
         def yielding_arguments?(block_args, yield_args)
           yield_args = yield_args.dup.fill(
             nil,
@@ -91,15 +101,15 @@ def yielding_arguments?(block_args, yield_args)
           end
         end
 
-        def add_block_argument(node, corrector)
+        def add_block_argument(node, corrector, block_name)
           if node.arguments?
-            insert_argument(node, corrector)
+            insert_argument(node, corrector, block_name)
           elsif empty_arguments?(node)
-            corrector.replace(node.arguments, '(&block)')
+            corrector.replace(node.arguments, "(&#{block_name})")
           elsif call_like?(node)
-            correct_call_node(node, corrector)
+            correct_call_node(node, corrector, block_name)
           else
-            corrector.insert_after(node.loc.name, '(&block)')
+            corrector.insert_after(node.loc.name, "(&#{block_name})")
           end
         end
 
@@ -112,16 +122,16 @@ def call_like?(node)
           node.call_type? || node.zsuper_type? || node.super_type?
         end
 
-        def insert_argument(node, corrector)
+        def insert_argument(node, corrector, block_name)
           last_arg = node.arguments.last
           arg_range = range_with_surrounding_comma(last_arg.source_range, :right)
-          replacement = ' &block'
+          replacement = " &#{block_name}"
           replacement = ",#{replacement}" unless arg_range.source.end_with?(',')
           corrector.insert_after(arg_range, replacement) unless last_arg.blockarg_type?
         end
 
-        def correct_call_node(node, corrector)
-          corrector.insert_after(node, '(&block)')
+        def correct_call_node(node, corrector, block_name)
+          corrector.insert_after(node, "(&#{block_name})")
           return unless node.parenthesized?
 
           args_begin = Util.args_begin(node)

spec/rubocop/cop/style/explicit_block_argument_spec.rb

@@ -41,15 +41,15 @@ def m
 
   it 'correctly corrects when method already has an explicit block argument' do
     expect_offense(<<~RUBY)
-      def m(&block)
+      def m(&blk)
         items.something { |i| yield i }
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Consider using explicit block argument in the surrounding method's signature over `yield`.
       end
     RUBY
 
     expect_correction(<<~RUBY)
-      def m(&block)
-        items.something(&block)
+      def m(&blk)
+        items.something(&blk)
       end
     RUBY
   end