Define the EntryExistsError message within the error class.

lib/zip/errors.rb

@@ -2,7 +2,6 @@
 
 module Zip
   class Error < StandardError; end
-  class EntryExistsError < Error; end
   class DestinationFileExistsError < Error; end
   class EntryNameError < Error; end
   class EntrySizeError < Error; end
@@ -33,6 +32,18 @@ module Zip
     end
   end
 
+  class EntryExistsError < Error
+    def initialize(source, name)
+      super()
+      @source = source
+      @name = name
+    end
+
+    def message
+      "'#{@source}' failed. Entry #{@name} already exists."
+    end
+  end
+
   class SplitArchiveError < Error
     def message
       'Rubyzip cannot extract from split archives at this time.'

lib/zip/file.rb

@@ -362,15 +362,12 @@ module Zip
     end
 
     def check_entry_exists(entry_name, continue_on_exists_proc, proc_name)
-      continue_on_exists_proc ||= proc { Zip.continue_on_exists_proc }
       return unless @cdir.include?(entry_name)
 
-      if continue_on_exists_proc.call
-        remove get_entry(entry_name)
-      else
-        raise ::Zip::EntryExistsError,
-              proc_name + " failed. Entry #{entry_name} already exists"
-      end
+      continue_on_exists_proc ||= proc { Zip.continue_on_exists_proc }
+      raise ::Zip::EntryExistsError.new proc_name, entry_name unless continue_on_exists_proc.call
+
+      remove get_entry(entry_name)
     end
 
     def check_file(path)

test/case_sensitivity_test.rb

@@ -40,9 +40,10 @@ class ZipCaseSensitivityTest < MiniTest::Test
     SRC_FILES.each { |fn, _en| assert(::File.exist?(fn)) }
     zf = ::Zip::File.new(EMPTY_FILENAME, create: true)
 
-    assert_raises Zip::EntryExistsError do
+    error = assert_raises Zip::EntryExistsError do
       SRC_FILES.each { |fn, en| zf.add(en, fn) }
     end
+    assert_match(/'add'/, error.message)
   end
 
   # Ensure that names are treated case insensitively when reading files and +case_insensitive_match = true+

test/file_test.rb

@@ -389,11 +389,12 @@ class ZipFileTest < MiniTest::Test
   end
 
   def test_add_existing_entry_name
-    assert_raises(::Zip::EntryExistsError) do
+    error = assert_raises(::Zip::EntryExistsError) do
       ::Zip::File.open(TEST_ZIP.zip_name) do |zf|
         zf.add(zf.entries.first.name, 'test/data/file2.txt')
       end
     end
+    assert_match(/'add'/, error.message)
   end
 
   def test_add_existing_entry_name_replace
@@ -538,11 +539,12 @@ class ZipFileTest < MiniTest::Test
     old_entries = nil
     ::Zip::File.open(TEST_ZIP.zip_name) { |zf| old_entries = zf.entries }
 
-    assert_raises(::Zip::EntryExistsError) do
+    error = assert_raises(::Zip::EntryExistsError) do
       ::Zip::File.open(TEST_ZIP.zip_name) do |zf|
         zf.rename(zf.entries[0], zf.entries[1].name)
       end
     end
+    assert_match(/'rename'/, error.message)
 
     ::Zip::File.open(TEST_ZIP.zip_name) do |zf|
       assert_equal(old_entries.sort.map(&:name), zf.entries.sort.map(&:name))
@@ -586,7 +588,10 @@ class ZipFileTest < MiniTest::Test
   def test_rename_entry_to_existing_entry
     entry1, entry2, * = TEST_ZIP.entry_names
     zf = ::Zip::File.new(TEST_ZIP.zip_name)
-    assert_raises(::Zip::EntryExistsError) { zf.rename(entry1, entry2) }
+    error = assert_raises(::Zip::EntryExistsError) do
+      zf.rename(entry1, entry2)
+    end
+    assert_match(/'rename'/, error.message)
   ensure
     zf.close
   end

test/settings_test.rb

@@ -46,11 +46,12 @@ class ZipSettingsTest < MiniTest::Test
   def test_false_continue_on_exists_proc
     Zip.continue_on_exists_proc = false
 
-    assert_raises(::Zip::EntryExistsError) do
+    error = assert_raises(::Zip::EntryExistsError) do
       ::Zip::File.open(TEST_ZIP.zip_name) do |zf|
         zf.add(zf.entries.first.name, 'test/data/file2.txt')
       end
     end
+    assert_match(/'add'/, error.message)
   end
 
   def test_true_continue_on_exists_proc