Extract logic history_file in helper

lib/irb/history.rb

@@ -19,6 +19,32 @@ def infinite?
         save_history.negative?
       end
 
+      # Might be nil when HOME and XDG_CONFIG_HOME are not available.
+      def history_file
+        if (history_file = IRB.conf[:HISTORY_FILE])
+          File.expand_path(history_file)
+        else
+          IRB.rc_file("_history")
+        end
+      end
+
+      def history_file_present
+        history_file if history_file && File.exist?(history_file)
+      end
+
+      def folder_writable?
+        history_file && Pathname.new(history_file).dirname.writable?
+      end
+
+      def append?(history_file, loaded_mtime)
+        File.exist?(history_file) &&
+          File.mtime(history_file) != loaded_mtime
+      end
+
+      def file_encoding
+        IRB.conf[:LC_MESSAGES].encoding
+      end
+
       private
 
       def save_history_max
@@ -40,12 +66,8 @@ def reset_history_counter
     def load_history
       history = self.class::HISTORY
 
-      if history_file = IRB.conf[:HISTORY_FILE]
-        history_file = File.expand_path(history_file)
-      end
-      history_file = IRB.rc_file("_history") unless history_file
-      if history_file && File.exist?(history_file)
-        File.open(history_file, "r:#{IRB.conf[:LC_MESSAGES].encoding}") do |f|
+      if (history_file = History.history_file_present)
+        File.open(history_file, "r:#{History.file_encoding}") do |f|
           f.each { |l|
             l = l.chomp
             if self.class == RelineInputMethod and history.last&.end_with?("\\")
@@ -62,50 +84,48 @@ def load_history
     end
 
     def save_history
+      return unless History.save_history?
+      return unless (history_file = History.history_file)
+      unless History.folder_writable? && correct_permissions!(history_file)
+        warn <<~WARN
+          Can't write history to #{History.history_file.inspect} due to insufficient permissions.
+          Please verify the value of `IRB.conf[:HISTORY_FILE]`. Ensure the folder exists and that both the folder and file (if it exists) are writable.
+        WARN
+        return
+      end
+
       history = self.class::HISTORY.to_a
 
-      if History.save_history?
-        if history_file = IRB.conf[:HISTORY_FILE]
-          history_file = File.expand_path(history_file)
-        end
-        history_file = IRB.rc_file("_history") unless history_file
-
-        # When HOME and XDG_CONFIG_HOME are not available, history_file might be nil
-        return unless history_file
-
-        # Change the permission of a file that already exists[BUG #7694]
-        begin
-          if File.stat(history_file).mode & 066 != 0
-            File.chmod(0600, history_file)
-          end
-        rescue Errno::ENOENT
-        rescue Errno::EPERM
-          return
-        rescue
-          raise
-        end
+      if History.append?(history_file, @loaded_history_mtime)
+        history = history[@loaded_history_lines..-1] if @loaded_history_lines
+        append_history = true
+      end
 
-        if File.exist?(history_file) &&
-           File.mtime(history_file) != @loaded_history_mtime
-          history = history[@loaded_history_lines..-1] if @loaded_history_lines
-          append_history = true
-        end
+      File.open(history_file, (append_history ? "a" : "w"), 0o600, encoding: History.file_encoding) do |f|
+        hist = history.map { |l| l.scrub.split("\n").join("\\\n") }
 
-        pathname = Pathname.new(history_file)
-        unless Dir.exist?(pathname.dirname)
-          warn "Warning: The directory to save IRB's history file does not exist. Please double check `IRB.conf[:HISTORY_FILE]`'s value."
-          return
+        unless append_history || History.infinite?
+          hist = hist.last(History.save_history)
         end
 
-        File.open(history_file, (append_history ? 'a' : 'w'), 0o600, encoding: IRB.conf[:LC_MESSAGES]&.encoding) do |f|
-          hist = history.map{ |l| l.scrub.split("\n").join("\\\n") }
+        f.puts(hist)
+      end
+    end
+
+    private
 
-          unless append_history || History.infinite?
-            hist = hist.last(History.save_history)
-          end
+    # Ensure existing +history_file+ is owner-only-readable [BUG #7694].
+    # Yields boolean whether chmod succeeded. `true` when file is absent.
+    def correct_permissions!(history_file)
+      return true unless File.exist?(history_file)
 
-          f.puts(hist)
+      begin
+        if File.stat(history_file).mode & 0o66 != 0
+          File.chmod(0o600, history_file)
         end
+        true
+      rescue Errno::EPERM # no permissions
+        false
       end
     end
   end

test/irb/test_history.rb

@@ -181,7 +181,7 @@ def test_history_does_not_raise_when_history_file_directory_does_not_exist
       IRB.conf[:HISTORY_FILE] = "fake/fake/fake/history_file"
       io = TestInputMethodWithRelineHistory.new
 
-      assert_warn(/history file does not exist/) do
+      assert_warn(/ensure the folder exists/i) do
         io.save_history
       end