webdriver_server: allow script timeout to be optional

The script timeout duration may be set to null, indicating that an
injected script should run indefinitely without getting interrupted.
This change fixes the internal data structure, but does not address the
parsing of the input arguments to handle_set_timeouts.

components/webdriver_server/lib.rs

@@ -101,8 +101,9 @@ struct WebDriverSession {
     id: Uuid,
     frame_id: Option<FrameId>,
 
-    /// Time to wait for injected scripts to run before interrupting them.
-    script_timeout: u32,
+    /// Time to wait for injected scripts to run before interrupting them.  A [`None`] value
+    /// specifies that the script should run indefinitely.
+    script_timeout: Option<u32>,
 
     /// Time to wait for a page to finish loading upon navigation.
     load_timeout: u32,
@@ -118,7 +119,7 @@ impl WebDriverSession {
             id: Uuid::new_v4(),
             frame_id: None,
 
-            script_timeout: 30_000,
+            script_timeout: Some(30_000),
             load_timeout: 300_000,
             implicit_wait_timeout: 0,
         }
@@ -705,11 +706,10 @@ impl Handler {
             .as_mut()
             .ok_or(WebDriverError::new(ErrorStatus::SessionNotCreated, "")));
 
-        // TODO(ato): Conversation is wrong. The script timeout can be null, and the numeric
-        // values should be limited to u32 in the standard.
+        // TODO: this conversion is crazy, spec should limit these to u32 and check upstream
         let value = parameters.ms as u32;
         match &parameters.type_[..] {
-            "script" => session.script_timeout = value,
+            "script" => session.script_timeout = Some(value),
             "page load" => session.load_timeout = value,
             "implicit" => session.implicit_wait_timeout = value,
             x => {
@@ -745,10 +745,15 @@ impl Handler {
         let func_body = &parameters.script;
         let args_string = "window.webdriverCallback";
 
-        let script = format!("setTimeout(webdriverTimeout, {}); (function(callback) {{ {} }})({})",
-                             session.script_timeout,
-                             func_body,
-                             args_string);
+        let script = match session.script_timeout {
+            Some(timeout) => {
+                format!("setTimeout(webdriverTimeout, {}); (function(callback) {{ {} }})({})",
+                        timeout,
+                        func_body,
+                        args_string)
+            }
+            None => format!("(function(callback) {{ {} }})({})", func_body, args_string),
+        };
 
         let (sender, receiver) = ipc::channel().unwrap();
         let command = WebDriverScriptCommand::ExecuteAsyncScript(script, sender);