Improve offense message for RSpec/IndexedLet

Ran into this offense and thought:
> Where exactly does my name contain "index"?

I believe this message format is more clear.

CHANGELOG.md

@@ -3,6 +3,7 @@
 ## Master (Unreleased)
 
 - Fix false-negative and error for `RSpec/MetadataStyle` when non-literal args are used in metadata in `EnforceStyle: hash`. ([@cbliard])
+- Improve offense message for `RSpec/IndexedLet`. ([@earlopain])
 
 ## 3.0.4 (2024-08-05)
 

lib/rubocop/cop/rspec/indexed_let.rb

@@ -48,8 +48,8 @@ class IndexedLet < Base
         include AllowedIdentifiers
         include AllowedPattern
 
-        MSG = 'This `let` statement uses index in its name. Please give it ' \
-              'a meaningful name.'
+        MSG = 'This `let` statement uses `%<index>s` in its name. ' \
+              'Please give it a meaningful name.'
 
         # @!method let_name(node)
         def_node_matcher :let_name, <<~PATTERN
@@ -66,7 +66,8 @@ def on_block(node) # rubocop:disable InternalAffairs/NumblockHandler
           return unless children
 
           filter_indexed_lets(children).each do |let_node|
-            add_offense(let_node)
+            index = let_name(let_node)[INDEX_REGEX]
+            add_offense(let_node, message: format(MSG, index: index))
           end
         end
 

spec/rubocop/cli/run_spec.rb

@@ -39,9 +39,9 @@
         == spec/example.rb ==
         C:  2:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
         C:  3:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
-        C:  6:  3: RSpec/IndexedLet: This let statement uses index in its name. Please give it a meaningful name.
+        C:  6:  3: RSpec/IndexedLet: This let statement uses 1 in its name. Please give it a meaningful name.
         C:  6:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
-        C:  7:  3: RSpec/IndexedLet: This let statement uses index in its name. Please give it a meaningful name.
+        C:  7:  3: RSpec/IndexedLet: This let statement uses 2 in its name. Please give it a meaningful name.
         C:  7:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
 
         1 file inspected, 6 offenses detected
@@ -82,9 +82,9 @@
         == spec/example.rb ==
         C:  2:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
         C:  3:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
-        C:  6:  3: RSpec/IndexedLet: This let statement uses index in its name. Please give it a meaningful name.
+        C:  6:  3: RSpec/IndexedLet: This let statement uses 1 in its name. Please give it a meaningful name.
         C:  6:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
-        C:  7:  3: RSpec/IndexedLet: This let statement uses index in its name. Please give it a meaningful name.
+        C:  7:  3: RSpec/IndexedLet: This let statement uses 2 in its name. Please give it a meaningful name.
         C:  7:  7: Naming/VariableNumber: Use normalcase for symbol numbers.
 
         1 file inspected, 6 offenses detected

spec/rubocop/cop/rspec/indexed_let_spec.rb

@@ -16,9 +16,9 @@
     expect_offense(<<~RUBY)
       describe SomeService do
         let(:item_1) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let(:item_2) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `2` in its name. Please give it a meaningful name.
       end
     RUBY
   end
@@ -27,9 +27,9 @@
     expect_offense(<<~RUBY)
       describe SomeService do
         let("item_1") { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let("item_2") { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `2` in its name. Please give it a meaningful name.
       end
     RUBY
   end
@@ -38,9 +38,9 @@
     expect_offense(<<~RUBY)
       describe SomeService do
         let(:item1) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let(:item2) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `2` in its name. Please give it a meaningful name.
       end
     RUBY
   end
@@ -49,9 +49,9 @@
     expect_offense(<<~RUBY)
       describe SomeService do
         let(:item_1, &block)
-        ^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let(:item_2, &block)
-        ^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `2` in its name. Please give it a meaningful name.
       end
     RUBY
   end
@@ -72,11 +72,11 @@
     expect_offense(<<~RUBY)
       context SomeService do
         let(:user_1_item_1) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let(:user_1_item_2) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let(:user_2_item_1) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `2` in its name. Please give it a meaningful name.
       end
     RUBY
   end
@@ -112,9 +112,9 @@
     expect_offense(<<~RUBY)
       describe SomeService do
         let(:item_1) { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `1` in its name. Please give it a meaningful name.
         let("item_2") { create(:item) }
-        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses index in its name. Please give it a meaningful name.
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This `let` statement uses `2` in its name. Please give it a meaningful name.
       end
     RUBY
   end