add Document#entity_expansion_text_limit=

## Why?
See: ruby#192

lib/rexml/attribute.rb

@@ -148,8 +148,12 @@ def to_s
     # have been expanded to their values
     def value
       return @unnormalized if @unnormalized
-      @unnormalized = Text::unnormalize( @normalized, doctype )
-      @unnormalized
+
+      if @element&.document
+        @unnormalized = Text::unnormalize(@normalized, doctype, entity_expansion_text_limit: @element.document.entity_expansion_text_limit)
+      else
+        @unnormalized = Text::unnormalize(@normalized, doctype)
+      end
     end
 
     # The normalized value of this attribute.  That is, the attribute with

lib/rexml/document.rb

@@ -92,6 +92,7 @@ class Document < Element
     def initialize( source = nil, context = {} )
       @entity_expansion_count = 0
       @entity_expansion_limit = Security.entity_expansion_limit
+      @entity_expansion_text_limit = Security.entity_expansion_text_limit
       super()
       @context = context
       return if source.nil?
@@ -432,6 +433,7 @@ def Document::entity_expansion_text_limit
     end
 
     attr_reader :entity_expansion_count
+    attr_accessor :entity_expansion_text_limit
 
     def record_entity_expansion
       @entity_expansion_count += 1

lib/rexml/entity.rb

@@ -71,9 +71,14 @@ def Entity::matches? string
     # Evaluates to the unnormalized value of this entity; that is, replacing
     # &ent; entities.
     def unnormalized
-      document.record_entity_expansion unless document.nil?
       return nil if @value.nil?
-      @unnormalized = Text::unnormalize(@value, parent)
+
+      if document.nil?
+        @unnormalized = Text::unnormalize(@value, parent)
+      else
+        document.record_entity_expansion
+        @unnormalized = Text::unnormalize(@value, parent, entity_expansion_text_limit: document.entity_expansion_text_limit)
+      end
     end
 
     #once :unnormalized

lib/rexml/text.rb

@@ -268,7 +268,11 @@ def inspect
     #   u = Text.new( "sean russell", false, nil, true )
     #   u.value   #-> "sean russell"
     def value
-      @unnormalized ||= Text::unnormalize( @string, doctype )
+      if document.nil?
+        @unnormalized ||= Text::unnormalize(@string, doctype)
+      else
+        @unnormalized ||= Text::unnormalize(@string, doctype, entity_expansion_text_limit: document.entity_expansion_text_limit)
+      end
     end
 
     # Sets the contents of this text node.  This expects the text to be
@@ -411,11 +415,11 @@ def Text::normalize( input, doctype=nil, entity_filter=nil )
     end
 
     # Unescapes all possible entities
-    def Text::unnormalize( string, doctype=nil, filter=nil, illegal=nil )
+    def Text::unnormalize( string, doctype=nil, filter=nil, illegal=nil, entity_expansion_text_limit: Security.entity_expansion_text_limit )
       sum = 0
       string.gsub( /\r\n?/, "\n" ).gsub( REFERENCE ) {
         s = Text.expand($&, doctype, filter)
-        if sum + s.bytesize > Security.entity_expansion_text_limit
+        if sum + s.bytesize > entity_expansion_text_limit
           raise "entity expansion has grown too large"
         else
           sum += s.bytesize

test/test_document.rb

@@ -31,14 +31,6 @@ def test_new
     end
 
     class EntityExpansionLimitTest < Test::Unit::TestCase
-      def setup
-        @default_entity_expansion_text_limit = REXML::Security.entity_expansion_text_limit
-      end
-
-      def teardown
-        REXML::Security.entity_expansion_text_limit = @default_entity_expansion_text_limit
-      end
-
       class GeneralEntityTest < self
         def test_have_value
           xml = <<XML
@@ -138,8 +130,8 @@ def test_entity_expansion_text_limit
 <member>&a;</member>
           XML
 
-          REXML::Security.entity_expansion_text_limit = 90
           doc = REXML::Document.new(xml)
+          doc.entity_expansion_text_limit = 90
           assert_equal(90, doc.root.children.first.value.bytesize)
         end
       end