Refactor Checksum cop to add autocorrect method

Library/.rubocop.yml

@@ -15,6 +15,9 @@ FormulaAudit/Caveats:
 FormulaAudit/Checksum:
   Enabled: true
 
+FormulaAudit/ChecksumCase:
+  Enabled: true
+
 FormulaAuditStrict/BottleBlock:
   Enabled: true
 

Library/Homebrew/rubocops/checksum_cop.rb

@@ -21,15 +21,6 @@ module RuboCop
           end
         end
 
-        def get_checksum_node(call)
-          return if parameters(call).empty? || parameters(call).nil?
-          if parameters(call).first.str_type?
-            parameters(call).first
-          elsif parameters(call).first.hash_type?
-            parameters(call).first.keys.first
-          end
-        end
-
         def audit_sha256(checksum)
           return if checksum.nil?
           if regex_match_group(checksum, /^$/)
@@ -41,12 +32,31 @@ module RuboCop
             problem "sha256 should be 64 characters"
           end
 
-          if regex_match_group(checksum, /[^a-f0-9]+/i)
-            problem "sha256 contains invalid characters"
-          end
+          return unless regex_match_group(checksum, /[^a-f0-9]+/i)
+          problem "sha256 contains invalid characters"
+        end
+      end
 
-          return unless regex_match_group(checksum, /[A-F]+/)
-          problem "sha256 should be lowercase"
+      class ChecksumCase < FormulaCop
+        def audit_formula(_node, _class_node, _parent_class_node, body_node)
+          return if body_node.nil?
+          sha256_calls = find_every_method_call_by_name(body_node, :sha256)
+          sha256_calls.each do |sha256_call|
+            checksum = get_checksum_node(sha256_call)
+            next if checksum.nil?
+            next unless regex_match_group(checksum, /[A-F]+/)
+            problem "sha256 should be lowercase"
+          end
+        end
+
+        private
+
+        def autocorrect(node)
+          lambda do |corrector|
+            correction = node.source.downcase
+            corrector.insert_before(node.source_range, correction)
+            corrector.remove(node.source_range)
+          end
         end
       end
     end

Library/Homebrew/rubocops/extend/formula_cop.rb

@@ -277,6 +277,17 @@ module RuboCop
         end
       end
 
+      # Returns the sha256 str node given a sha256 call node
+      def get_checksum_node(call)
+        return if parameters(call).empty? || parameters(call).nil?
+        if parameters(call).first.str_type?
+          parameters(call).first
+        # sha256 is passed as a key-value pair in bottle blocks
+        elsif parameters(call).first.hash_type?
+          parameters(call).first.keys.first
+        end
+      end
+
       # Returns the begin position of the node's line in source code
       def line_start_column(node)
         node.source_range.source_buffer.line_range(node.loc.line).begin_pos

Library/Homebrew/test/rubocops/checksum_cop_spec.rb

@@ -108,7 +108,13 @@ describe RuboCop::Cop::FormulaAudit::Checksum do
         expect_offense(expected, actual)
       end
     end
+  end
+end
 
+describe RuboCop::Cop::FormulaAudit::ChecksumCase do
+  subject(:cop) { described_class.new }
+
+  context "When auditing spec checksums" do
     it "When the checksum has upper case characters" do
       source = <<-EOS.undent
         class Foo < Formula
@@ -176,4 +182,41 @@ describe RuboCop::Cop::FormulaAudit::Checksum do
       end
     end
   end
+
+  context "When auditing checksum with autocorrect" do
+    it "When there is uppercase sha256" do
+      source = <<-EOS.undent
+        class Foo < Formula
+          url 'http://example.com/foo-1.0.tgz'
+          stable do
+            url "https://github.com/foo-lang/foo-compiler/archive/0.18.0.tar.gz"
+            sha256 "5cf6e1ae0A645b426c0a7cc7cd3f7d1605ffa1ac5756a39a8b2268ddc7ea0e9a"
+
+            resource "foo-package" do
+              url "https://github.com/foo-lang/foo-package/archive/0.18.0.tar.gz"
+              sha256 "5cf6e1Ae0a645b426b047aa4cc7cd3f7d1605ffa1ac5756a39a8b2268ddc7ea9"
+            end
+          end
+        end
+      EOS
+
+      corrected_source = <<-EOS.undent
+        class Foo < Formula
+          url 'http://example.com/foo-1.0.tgz'
+          stable do
+            url "https://github.com/foo-lang/foo-compiler/archive/0.18.0.tar.gz"
+            sha256 "5cf6e1ae0a645b426c0a7cc7cd3f7d1605ffa1ac5756a39a8b2268ddc7ea0e9a"
+
+            resource "foo-package" do
+              url "https://github.com/foo-lang/foo-package/archive/0.18.0.tar.gz"
+              sha256 "5cf6e1ae0a645b426b047aa4cc7cd3f7d1605ffa1ac5756a39a8b2268ddc7ea9"
+            end
+          end
+        end
+      EOS
+
+      new_source = autocorrect_source(cop, source)
+      expect(new_source).to eq(corrected_source)
+    end
+  end
 end