quick hack: hijacks the predicate RDoc::Parser.binary? so that it does not consider a handful of ordinary Ruby files in the Rails tree as binary (and thus excluded from the API)

Rakefile

@@ -5,6 +5,31 @@ require 'rake'
 require 'rdoc/task'
 require 'rake/gempackagetask'
 
+# RDoc skips some files in the Rails tree due to its binary? predicate. This is a quick
+# hack for edge docs, until we decide which is the correct way to address this issue.
+# If not fixed in RDoc itself, via an option or something, we should probably move this
+# to railties and use it also in doc:rails.
+def hijack_rdoc!
+  require "rdoc/parser"
+  class << RDoc::Parser
+    def binary?(file)
+      s = File.read(file, 1024) or return false
+
+      if s[0, 2] == Marshal.dump('')[0, 2] then
+        true
+      elsif file =~ /\.erb\.rb$/ then # ORIGINAL is file =~ /erb\.rb$/
+        false
+      elsif s.index("\x00") then # ORIGINAL is s.scan(/<%|%>/).length >= 4 || s.index("\x00")
+        true
+      elsif 0.respond_to? :fdiv then
+        s.count("^ -~\t\r\n").fdiv(s.size) > 0.3
+      else # HACK 1.8.6
+        (s.count("^ -~\t\r\n").to_f / s.size) > 0.3
+      end
+    end
+  end
+end
+
 PROJECTS = %w(activesupport activemodel actionpack actionmailer activeresource activerecord railties)
 
 desc 'Run all tests by default'
@@ -63,6 +88,8 @@ end
 
 desc "Generate documentation for the Rails framework"
 RDoc::Task.new do |rdoc|
+  hijack_rdoc!
+
   rdoc.rdoc_dir = 'doc/rdoc'
   rdoc.title    = "Ruby on Rails Documentation"