Add internal command to calculate appcast checkpoint.

Library/Homebrew/cask/lib/hbc/audit.rb

@@ -133,20 +133,19 @@ module Hbc
 
     def check_appcast_checkpoint_accuracy
       odebug "Verifying appcast checkpoint is accurate"
-      result = @command.run("/usr/bin/curl", args: ["--compressed", "--location", "--user-agent", URL::FAKE_USER_AGENT, cask.appcast], print_stderr: false)
-      if result.success?
-        processed_appcast_text = result.stdout.gsub(%r{<pubDate>[^<]*</pubDate>}, "")
-        # This step is necessary to replicate running `sed` from the command line
-        processed_appcast_text << "\n" unless processed_appcast_text.end_with?("\n")
+      result = cask.appcast.calculate_checkpoint
+
+      actual_checkpoint = result[:checkpoint]
+
+      if actual_checkpoint.nil?
+        add_warning "error retrieving appcast: #{result[:command_result].stderr}"
+      else
         expected = cask.appcast.checkpoint
-        actual = Digest::SHA2.hexdigest(processed_appcast_text)
-        add_warning <<-EOS.undent unless expected == actual
+        add_warning <<-EOS.undent unless expected == actual_checkpoint
           appcast checkpoint mismatch
           Expected: #{expected}
-          Actual: #{actual}
+          Actual: #{actual_checkpoint}
         EOS
-      else
-        add_warning "error retrieving appcast: #{result.stderr}"
       end
     end
 

Library/Homebrew/cask/lib/hbc/cli.rb

@@ -23,6 +23,7 @@ require "hbc/cli/zap"
 
 require "hbc/cli/internal_use_base"
 require "hbc/cli/internal_audit_modified_casks"
+require "hbc/cli/internal_appcast_checkpoint"
 require "hbc/cli/internal_checkurl"
 require "hbc/cli/internal_dump"
 require "hbc/cli/internal_help"

Library/Homebrew/cask/lib/hbc/cli/internal_appcast_checkpoint.rb

@@ -0,0 +1,45 @@
+module Hbc
+  class CLI
+    class InternalAppcastCheckpoint < InternalUseBase
+      def self.run(*args)
+        cask_tokens = cask_tokens_from(args)
+        raise CaskUnspecifiedError if cask_tokens.empty?
+
+        appcask_checkpoint(cask_tokens)
+      end
+
+      def self.appcask_checkpoint(cask_tokens)
+        count = 0
+
+        cask_tokens.each do |cask_token|
+          cask = Hbc.load(cask_token)
+
+          if cask.appcast.nil?
+            opoo "Cask '#{cask}' is missing an `appcast` stanza."
+          else
+            result = cask.appcast.calculate_checkpoint
+
+            checkpoint = result[:checkpoint]
+
+            if checkpoint.nil?
+              onoe "Could not retrieve `appcast` checkpoint for cask '#{cask}': #{result[:command_result].stderr}"
+            else
+              puts cask_tokens.count > 1 ? "#{checkpoint}  #{cask}": checkpoint
+              count += 1
+            end
+          end
+        end
+
+        count == cask_tokens.count
+      end
+
+      def self.help
+        "calculates a given Cask's appcast checkpoint"
+      end
+
+      def self.needs_init?
+        true
+      end
+    end
+  end
+end

Library/Homebrew/cask/lib/hbc/dsl/appcast.rb

@@ -1,3 +1,5 @@
+require "hbc/system_command"
+
 module Hbc
   class DSL
     class Appcast
@@ -9,6 +11,24 @@ module Hbc
         @checkpoint     = @parameters[:checkpoint]
       end
 
+      def calculate_checkpoint
+        result = SystemCommand.run("/usr/bin/curl", args: ["--compressed", "--location", "--user-agent", URL::FAKE_USER_AGENT, @uri], print_stderr: false)
+
+        checkpoint = if result.success?
+          processed_appcast_text = result.stdout.gsub(%r{<pubDate>[^<]*</pubDate>}, "")
+
+          # This step is necessary to replicate running `sed` from the command line
+          processed_appcast_text << "\n" unless processed_appcast_text.end_with?("\n")
+
+          Digest::SHA2.hexdigest(processed_appcast_text)
+        end
+
+        {
+          checkpoint: checkpoint,
+          command_result: result,
+        }
+      end
+
       def to_yaml
         [@uri, @parameters].to_yaml
       end

Library/Homebrew/cask/spec/cask/audit_spec.rb

@@ -162,7 +162,7 @@ describe Hbc::Audit do
 
         before do
           allow(audit).to receive(:check_appcast_http_code)
-          allow(fake_system_command).to receive(:run).and_return(fake_curl_result)
+          allow(Hbc::SystemCommand).to receive(:run).and_return(fake_curl_result)
           allow(fake_curl_result).to receive(:success?).and_return(success)
         end