Check nesting for blocks with one child

Library/Homebrew/rubocops/components_order.rb

@@ -116,6 +116,15 @@ module RuboCop
         end
 
         def check_on_system_block_content(component_precedence_list, on_system_block)
+          if on_system_block.body.block_type? && !on_system_methods.include?(on_system_block.body.method_name)
+            offending_node(on_system_block)
+            problem "Nest `#{on_system_block.method_name}` blocks inside `#{on_system_block.body.method_name}` " \
+                    "blocks when there is only one inner block." do |corrector|
+              original_source = on_system_block.source.split("\n")
+              new_source = [original_source.second, original_source.first, *original_source.drop(2)]
+              corrector.replace(on_system_block.source_range, new_source.join("\n"))
+            end
+          end
           on_system_allowed_methods = %w[
             depends_on
             patch

Library/Homebrew/test/rubocops/components_order_spec.rb

@@ -679,6 +679,130 @@ describe RuboCop::Cop::FormulaAudit::ComponentsOrder do
       RUBY
     end
 
+    it "reports an offense when a single `patch` block is inside the `on_arm` block" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+          on_arm do
+          ^^^^^^^^^ Nest `on_arm` blocks inside `patch` blocks when there is only one inner block.
+            patch do
+              url "https://brew.sh/patch1.tar.gz"
+              sha256 "2c39089f64d9d4c3e632f120894b36b68dcc8ae8c6f5130c0c2e6f5bb7aebf2f"
+            end
+          end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+              patch do
+        on_arm do
+              url "https://brew.sh/patch1.tar.gz"
+              sha256 "2c39089f64d9d4c3e632f120894b36b68dcc8ae8c6f5130c0c2e6f5bb7aebf2f"
+            end
+          end
+        end
+      RUBY
+    end
+
+    it "reports an offense when a single `resource` block is inside the `on_linux` block" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+          on_linux do
+          ^^^^^^^^^^^ Nest `on_linux` blocks inside `resource` blocks when there is only one inner block.
+            resource do
+              url "https://brew.sh/resource1.tar.gz"
+              sha256 "586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35"
+            end
+          end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+              resource do
+        on_linux do
+              url "https://brew.sh/resource1.tar.gz"
+              sha256 "586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35"
+            end
+          end
+        end
+      RUBY
+    end
+
+    it "reports an offense when a single `patch` block is inside the `on_monterey :or_newer` block" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+          on_monterey :or_newer do
+          ^^^^^^^^^^^^^^^^^^^^^^^^ Nest `on_monterey` blocks inside `patch` blocks when there is only one inner block.
+            patch do
+              url "https://brew.sh/patch1.tar.gz"
+              sha256 "2c39089f64d9d4c3e632f120894b36b68dcc8ae8c6f5130c0c2e6f5bb7aebf2f"
+            end
+          end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+              patch do
+        on_monterey :or_newer do
+              url "https://brew.sh/patch1.tar.gz"
+              sha256 "2c39089f64d9d4c3e632f120894b36b68dcc8ae8c6f5130c0c2e6f5bb7aebf2f"
+            end
+          end
+        end
+      RUBY
+    end
+
+    it "reports an offense when a single `resource` block is inside the `on_system` block" do
+      expect_offense(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+          on_system :linux, macos: :monterey_or_older do
+          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Nest `on_system` blocks inside `resource` blocks when there is only one inner block.
+            resource do
+              url "https://brew.sh/resource1.tar.gz"
+              sha256 "586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35"
+            end
+          end
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+              resource do
+        on_system :linux, macos: :monterey_or_older do
+              url "https://brew.sh/resource1.tar.gz"
+              sha256 "586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35"
+            end
+          end
+        end
+      RUBY
+    end
+
+    it "reports no offenses when a single `on_arm` block is inside the `on_macos` block" do
+      expect_no_offenses(<<~RUBY)
+        class Foo < Formula
+          url "https://brew.sh/foo-1.0.tgz"
+          on_macos do
+            on_arm do
+              resource do
+                url "https://brew.sh/resource1.tar.gz"
+                sha256 "586372eb92059873e29eba4f9dec8381541b4d3834660707faf8ba59146dfc35"
+              end
+            end
+          end
+        end
+      RUBY
+    end
+
     context "when in a resource block" do
       it "reports no offenses for a valid `on_macos` and `on_linux` block" do
         expect_no_offenses(<<~RUBY)