Serve the text-only page for non-graphical browsers. See #79.

lib/better_errors/middleware.rb

@@ -74,18 +74,25 @@ def protected_app_call(env)
       log_exception
       show_error_page(env)
     end
-    
+
     def show_error_page(env)
-      content = if @error_page
-        @error_page.render
+      type, content = if @error_page
+        if text?(env)
+          [ 'plain', @error_page.render('text') ]
+        else
+          [ 'html', @error_page.render ]
+        end
       else
-        "<h1>No errors</h1><p>No errors have been recorded yet.</p><hr>" +
-        "<code>Better Errors v#{BetterErrors::VERSION}</code>"
+        [ 'html', no_errors_page ]
       end
 
-      [500, { "Content-Type" => "text/html; charset=utf-8" }, [content]]
+      [500, { "Content-Type" => "text/#{type}; charset=utf-8" }, [content]]
     end
 
+    def text?(env)
+      env["HTTP_X_REQUESTED_WITH"] == "XMLHttpRequest" ||
+      !env["HTTP_ACCEPT"].to_s.include?('html')
+    end
 
     def log_exception
       return unless BetterErrors.logger
@@ -106,5 +113,10 @@ def internal_call(env, opts)
       response = @error_page.send("do_#{opts[:method]}", JSON.parse(env["rack.input"].read))
       [200, { "Content-Type" => "text/plain; charset=utf-8" }, [JSON.dump(response)]]
     end
+
+    def no_errors_page
+      "<h1>No errors</h1><p>No errors have been recorded yet.</p><hr>" +
+      "<code>Better Errors v#{BetterErrors::VERSION}</code>"
+    end
   end
 end

spec/better_errors/middleware_spec.rb

@@ -44,7 +44,20 @@ module BetterErrors
       it "should return UTF-8 error pages" do
         status, headers, body = app.call({})
 
-        headers["Content-Type"].should == "text/html; charset=utf-8"
+        headers["Content-Type"].should match /charset=utf-8/
+      end
+
+      it "should return text pages by default" do
+        status, headers, body = app.call({})
+
+        headers["Content-Type"].should match /text\/plain/
+      end
+
+      it "should return HTML pages by default" do
+        # Chrome's 'Accept' header looks similar this.
+        status, headers, body = app.call("HTTP_ACCEPT" => "text/html,application/xhtml+xml;q=0.9,*/*")
+
+        headers["Content-Type"].should match /text\/html/
       end
 
       it "should log the exception" do