Raise WebkitError for invalid XPath expressions

lib/capybara/driver/webkit.rb

@@ -3,6 +3,9 @@ require "capybara/driver/webkit/node"
 require "capybara/driver/webkit/browser"
 
 class Capybara::Driver::Webkit
+  class WebkitError < StandardError
+  end
+
   def initialize(app, options={})
     @app = app
     @options = options

lib/capybara/driver/webkit/browser.rb

@@ -44,7 +44,7 @@ class Capybara::Driver::Webkit
       result = @socket.gets.strip
       puts ">> #{result}"
       unless result == 'ok'
-        raise
+        raise WebkitError, read_response
       end
     end
 

spec/driver_spec.rb

@@ -18,17 +18,21 @@ describe Capybara::Driver::Webkit do
   end
 
   subject { Capybara::Driver::Webkit.new(hello_app) }
+  before { subject.visit("/hello") }
   after { subject.reset! }
 
   it "finds content after loading a URL" do
-    subject.visit("/hello")
     subject.find("//*[contains(., 'hello')]").should_not be_empty
   end
 
   it "has an empty page after reseting" do
-    subject.visit("/")
     subject.reset!
     subject.find("//*[contains(., 'hello')]").should be_empty
   end
+
+  it "raises an error for an invalid xpath query" do
+    expect { subject.find("totally invalid salad") }.
+      to raise_error(Capybara::Driver::Webkit::WebkitError, /xpath/i)
+  end
 end
 

src/Connection.cpp

@@ -64,11 +64,11 @@ void Connection::finishCommand(bool success, QString &response) {
   m_command = NULL;
   if (success) {
     m_socket->write("ok\n");
-    QString responseLength = QString::number(response.size()) + "\n";
-    m_socket->write(responseLength.toAscii());
-    m_socket->write(response.toAscii());
   } else {
     m_socket->write("failure\n");
   }
+  QString responseLength = QString::number(response.size()) + "\n";
+  m_socket->write(responseLength.toAscii());
+  m_socket->write(response.toAscii());
 }
 

src/Find.cpp

@@ -34,24 +34,29 @@ void Find::receivedArgument(const char *xpath) {
   std::cout << "<< Javascript to execute:" << std::endl;
   std::cout << javascript.toAscii().data() << std::endl;
 
+  QString response;
   QVariant result = page()->mainFrame()->evaluateJavaScript(javascript);
 
-  QVariantList nodes = result.toList();
-  QString response;
-  bool addComma = false;
+  if (result.isValid()) {
+    QVariantList nodes = result.toList();
+    bool addComma = false;
 
-  double node;
-  for (int i = 0; i < nodes.size(); i++) {
-    node = nodes[i].toDouble();
-    if (addComma)
-      response.append(",");
-    response.append(QString::number(node));
-    addComma = true;
+    double node;
+    for (int i = 0; i < nodes.size(); i++) {
+      node = nodes[i].toDouble();
+      if (addComma)
+        response.append(",");
+      response.append(QString::number(node));
+      addComma = true;
+    }
+
+    std::cout << "<< Got result:" << std::endl;
+    std::cout << response.toAscii().data() << std::endl;
+
+    emit finished(true, response);
+  } else {
+    response = "Invalid XPath expression";
+    emit finished(false, response);
   }
-
-  std::cout << "<< Got result:" << std::endl;
-  std::cout << response.toAscii().data() << std::endl;
-
-  emit finished(true, response);
 }