Scope ZIP64 disabling to save/stream instead of global config

PR #170 fixed #168 by setting Zip.write_zip64_support = false at the
top level when docx is required. That mutates global rubyzip state for
the whole host application, which can break other code that relies on
ZIP64 (flagged by Copilot review on #170).

Instead, disable ZIP64 only while writing in #save / #stream via a
with_zip64_disabled helper that restores the previous global value in
an ensure block, so other rubyzip users are unaffected. Adds regression
specs asserting the setting is not leaked after saving/streaming, and a
CHANGELOG entry.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: satoryu

lib/docx/document.rb

@@ -5,11 +5,6 @@
 require 'nokogiri'
 require 'zip'
 
-# Disable ZIP64 support to maintain compatibility with the previous default behavior
-# (before rubyzip 3.x) and ensure compatibility with all readers. Rubyzip 3.x enables
-# ZIP64 by default, but many readers (including pandoc) don't support it for small files.
-Zip.write_zip64_support = false
-
 module Docx
   # The Document class wraps around a docx file and provides methods to
   # interface with it.
@@ -133,40 +128,44 @@ def to_html
     # call-seq:
     #   save(filepath) => void
     def save(path)
-      update
-      Zip::OutputStream.open(path) do |out|
-        zip.each do |entry|
-          next unless entry.file?
+      with_zip64_disabled do
+        update
+        Zip::OutputStream.open(path) do |out|
+          zip.each do |entry|
+            next unless entry.file?
 
-          out.put_next_entry(entry.name)
-          value = @replace[entry.name] || zip.read(entry.name)
+            out.put_next_entry(entry.name)
+            value = @replace[entry.name] || zip.read(entry.name)
 
-          out.write(value)
-        end
+            out.write(value)
+          end
 
+        end
+        zip.close
       end
-      zip.close
     end
 
     # Output entire document as a StringIO object
     def stream
-      update
-      stream = Zip::OutputStream.write_buffer do |out|
-        zip.each do |entry|
-          next unless entry.file?
-
-          out.put_next_entry(entry.name)
-
-          if @replace[entry.name]
-            out.write(@replace[entry.name])
-          else
-            out.write(zip.read(entry.name))
+      with_zip64_disabled do
+        update
+        stream = Zip::OutputStream.write_buffer do |out|
+          zip.each do |entry|
+            next unless entry.file?
+
+            out.put_next_entry(entry.name)
+
+            if @replace[entry.name]
+              out.write(@replace[entry.name])
+            else
+              out.write(zip.read(entry.name))
+            end
           end
         end
-      end
 
-      stream.rewind
-      stream
+        stream.rewind
+        stream
+      end
     end
 
     alias text to_s
@@ -189,6 +188,18 @@ def styles_configuration
 
     private
 
+    # rubyzip 3.x enables ZIP64 by default, which breaks readers (e.g. pandoc)
+    # that don't support it for small files (issue #168). Disable ZIP64 only
+    # while writing, and restore the previous global value afterwards so we
+    # don't affect other rubyzip users in the consuming application.
+    def with_zip64_disabled
+      previous = Zip.write_zip64_support
+      Zip.write_zip64_support = false
+      yield
+    ensure
+      Zip.write_zip64_support = previous
+    end
+
     def load_styles
       @styles_xml = @zip.read('word/styles.xml')
       @styles = Nokogiri::XML(@styles_xml)

spec/docx/document_spec.rb

@@ -376,6 +376,31 @@
 
       after { File.delete(@new_doc_path) if File.exist?(@new_doc_path) }
     end
+
+    context 'ZIP64 global configuration' do
+      before { @doc = Docx::Document.open(@fixtures_path + '/basic.docx') }
+
+      around do |example|
+        previous = Zip.write_zip64_support
+        example.run
+        Zip.write_zip64_support = previous
+      end
+
+      it 'does not leak the disabled ZIP64 setting after saving' do
+        Zip.write_zip64_support = true
+        @new_doc_path = @fixtures_path + '/new_save.docx'
+        @doc.save(@new_doc_path)
+        expect(Zip.write_zip64_support).to eq(true)
+      end
+
+      it 'does not leak the disabled ZIP64 setting after streaming' do
+        Zip.write_zip64_support = true
+        @doc.stream
+        expect(Zip.write_zip64_support).to eq(true)
+      end
+
+      after { File.delete(@new_doc_path) if @new_doc_path && File.exist?(@new_doc_path) }
+    end
   end
 
   describe 'streaming' do