[WebDriver] Reuse "Find Elements" handler in "Find element" (#37737)

All "Find Element ..." in
[spec](https://w3c.github.io/webdriver/#find-element-from-element) has
exactly same step has "Find Elements ...", except they extract the first
element if there is any. We now reuse the handler instead of running
numerous repetitive steps, same as what we did for ["Find Element from
Shadow
Root"](https://w3c.github.io/webdriver/#find-element-from-shadow-root)
in #37578.

This reduces binary size by 98KB for Release profile in Windows and
improves maintainability.

Testing: `./mach test-wpt -r
.\tests\wpt\tests\webdriver\tests\classic\find_element* --product
servodriver`

---------

Signed-off-by: Euclid Ye <yezhizhenjiakang@gmail.com>

components/script/script_thread.rs

@@ -2247,33 +2247,6 @@ impl ScriptThread {
             WebDriverScriptCommand::DeleteCookie(name, reply) => {
                 webdriver_handlers::handle_delete_cookie(&documents, pipeline_id, name, reply)
             },
-            WebDriverScriptCommand::FindElementCSSSelector(selector, reply) => {
-                webdriver_handlers::handle_find_element_css_selector(
-                    &documents,
-                    pipeline_id,
-                    selector,
-                    reply,
-                )
-            },
-            WebDriverScriptCommand::FindElementLinkText(selector, partial, reply) => {
-                webdriver_handlers::handle_find_element_link_text(
-                    &documents,
-                    pipeline_id,
-                    selector,
-                    partial,
-                    reply,
-                    can_gc,
-                )
-            },
-            WebDriverScriptCommand::FindElementTagName(selector, reply) => {
-                webdriver_handlers::handle_find_element_tag_name(
-                    &documents,
-                    pipeline_id,
-                    selector,
-                    reply,
-                    can_gc,
-                )
-            },
             WebDriverScriptCommand::FindElementsCSSSelector(selector, reply) => {
                 webdriver_handlers::handle_find_elements_css_selector(
                     &documents,
@@ -2301,39 +2274,6 @@ impl ScriptThread {
                     can_gc,
                 )
             },
-            WebDriverScriptCommand::FindElementElementCSSSelector(selector, element_id, reply) => {
-                webdriver_handlers::handle_find_element_element_css_selector(
-                    &documents,
-                    pipeline_id,
-                    element_id,
-                    selector,
-                    reply,
-                )
-            },
-            WebDriverScriptCommand::FindElementElementLinkText(
-                selector,
-                element_id,
-                partial,
-                reply,
-            ) => webdriver_handlers::handle_find_element_element_link_text(
-                &documents,
-                pipeline_id,
-                element_id,
-                selector,
-                partial,
-                reply,
-                can_gc,
-            ),
-            WebDriverScriptCommand::FindElementElementTagName(selector, element_id, reply) => {
-                webdriver_handlers::handle_find_element_element_tag_name(
-                    &documents,
-                    pipeline_id,
-                    element_id,
-                    selector,
-                    reply,
-                    can_gc,
-                )
-            },
             WebDriverScriptCommand::FindElementElementsCSSSelector(selector, element_id, reply) => {
                 webdriver_handlers::handle_find_element_elements_css_selector(
                     &documents,

components/script/webdriver_handlers.rs

@@ -217,25 +217,6 @@ fn all_matching_links(
         .map(|nodes| matching_links(&nodes, link_text, partial, can_gc).collect())
 }
 
-fn first_matching_link(
-    root_node: &Node,
-    link_text: String,
-    partial: bool,
-    can_gc: CanGc,
-) -> Result<Option<String>, ErrorStatus> {
-    // <https://w3c.github.io/webdriver/#dfn-find>
-    // Step 7.2. If a DOMException, SyntaxError, XPathException, or other error occurs
-    // during the execution of the element location strategy, return error invalid selector.
-    root_node
-        .query_selector_all(DOMString::from("a"))
-        .map_err(|_| ErrorStatus::InvalidSelector)
-        .map(|nodes| {
-            matching_links(&nodes, link_text, partial, can_gc)
-                .take(1)
-                .next()
-        })
-}
-
 #[allow(unsafe_code)]
 unsafe fn object_has_to_json_property(
     cx: *mut JSContext,
@@ -714,65 +695,6 @@ fn retrieve_document_and_check_root_existence(
     }
 }
 
-pub(crate) fn handle_find_element_css_selector(
-    documents: &DocumentCollection,
-    pipeline: PipelineId,
-    selector: String,
-    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
-) {
-    match retrieve_document_and_check_root_existence(documents, pipeline) {
-        Ok(document) => reply
-            .send(
-                document
-                    .QuerySelector(DOMString::from(selector))
-                    .map_err(|_| ErrorStatus::InvalidSelector)
-                    .map(|element| element.map(|x| x.upcast::<Node>().unique_id(pipeline))),
-            )
-            .unwrap(),
-        Err(error) => reply.send(Err(error)).unwrap(),
-    }
-}
-
-pub(crate) fn handle_find_element_link_text(
-    documents: &DocumentCollection,
-    pipeline: PipelineId,
-    selector: String,
-    partial: bool,
-    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
-    can_gc: CanGc,
-) {
-    match retrieve_document_and_check_root_existence(documents, pipeline) {
-        Ok(document) => reply
-            .send(first_matching_link(
-                document.upcast::<Node>(),
-                selector.clone(),
-                partial,
-                can_gc,
-            ))
-            .unwrap(),
-        Err(error) => reply.send(Err(error)).unwrap(),
-    }
-}
-
-pub(crate) fn handle_find_element_tag_name(
-    documents: &DocumentCollection,
-    pipeline: PipelineId,
-    selector: String,
-    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
-    can_gc: CanGc,
-) {
-    match retrieve_document_and_check_root_existence(documents, pipeline) {
-        Ok(document) => reply
-            .send(Ok(document
-                .GetElementsByTagName(DOMString::from(selector), can_gc)
-                .elements_iter()
-                .next()
-                .map(|element| element.upcast::<Node>().unique_id(pipeline))))
-            .unwrap(),
-        Err(error) => reply.send(Err(error)).unwrap(),
-    }
-}
-
 pub(crate) fn handle_find_elements_css_selector(
     documents: &DocumentCollection,
     pipeline: PipelineId,
@@ -837,65 +759,6 @@ pub(crate) fn handle_find_elements_tag_name(
     }
 }
 
-pub(crate) fn handle_find_element_element_css_selector(
-    documents: &DocumentCollection,
-    pipeline: PipelineId,
-    element_id: String,
-    selector: String,
-    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
-) {
-    reply
-        .send(
-            get_known_element(documents, pipeline, element_id).and_then(|element| {
-                element
-                    .upcast::<Node>()
-                    .query_selector(DOMString::from(selector))
-                    .map_err(|_| ErrorStatus::InvalidSelector)
-                    .map(|element| element.map(|x| x.upcast::<Node>().unique_id(pipeline)))
-            }),
-        )
-        .unwrap();
-}
-
-pub(crate) fn handle_find_element_element_link_text(
-    documents: &DocumentCollection,
-    pipeline: PipelineId,
-    element_id: String,
-    selector: String,
-    partial: bool,
-    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
-    can_gc: CanGc,
-) {
-    reply
-        .send(
-            get_known_element(documents, pipeline, element_id).and_then(|element| {
-                first_matching_link(element.upcast::<Node>(), selector.clone(), partial, can_gc)
-            }),
-        )
-        .unwrap();
-}
-
-pub(crate) fn handle_find_element_element_tag_name(
-    documents: &DocumentCollection,
-    pipeline: PipelineId,
-    element_id: String,
-    selector: String,
-    reply: IpcSender<Result<Option<String>, ErrorStatus>>,
-    can_gc: CanGc,
-) {
-    reply
-        .send(
-            get_known_element(documents, pipeline, element_id).map(|element| {
-                element
-                    .GetElementsByTagName(DOMString::from(selector), can_gc)
-                    .elements_iter()
-                    .next()
-                    .map(|x| x.upcast::<Node>().unique_id(pipeline))
-            }),
-        )
-        .unwrap();
-}
-
 pub(crate) fn handle_find_element_elements_css_selector(
     documents: &DocumentCollection,
     pipeline: PipelineId,

components/shared/embedder/webdriver.rs

@@ -131,28 +131,9 @@ pub enum WebDriverScriptCommand {
     DeleteCookie(String, IpcSender<Result<(), ErrorStatus>>),
     ExecuteScript(String, IpcSender<WebDriverJSResult>),
     ExecuteAsyncScript(String, IpcSender<WebDriverJSResult>),
-    FindElementCSSSelector(String, IpcSender<Result<Option<String>, ErrorStatus>>),
-    FindElementLinkText(String, bool, IpcSender<Result<Option<String>, ErrorStatus>>),
-    FindElementTagName(String, IpcSender<Result<Option<String>, ErrorStatus>>),
     FindElementsCSSSelector(String, IpcSender<Result<Vec<String>, ErrorStatus>>),
     FindElementsLinkText(String, bool, IpcSender<Result<Vec<String>, ErrorStatus>>),
     FindElementsTagName(String, IpcSender<Result<Vec<String>, ErrorStatus>>),
-    FindElementElementCSSSelector(
-        String,
-        String,
-        IpcSender<Result<Option<String>, ErrorStatus>>,
-    ),
-    FindElementElementLinkText(
-        String,
-        String,
-        bool,
-        IpcSender<Result<Option<String>, ErrorStatus>>,
-    ),
-    FindElementElementTagName(
-        String,
-        String,
-        IpcSender<Result<Option<String>, ErrorStatus>>,
-    ),
     FindElementElementsCSSSelector(String, String, IpcSender<Result<Vec<String>, ErrorStatus>>),
     FindElementElementsLinkText(
         String,

components/webdriver_server/lib.rs

@@ -970,53 +970,11 @@ impl Handler {
         &self,
         parameters: &LocatorParameters,
     ) -> WebDriverResult<WebDriverResponse> {
-        // Step 4. If selector is undefined, return error with error code invalid argument.
-        if parameters.value.is_empty() {
-            return Err(WebDriverError::new(ErrorStatus::InvalidArgument, ""));
-        }
-        let (sender, receiver) = ipc::channel().unwrap();
-
-        match parameters.using {
-            LocatorStrategy::CSSSelector => {
-                let cmd = WebDriverScriptCommand::FindElementCSSSelector(
-                    parameters.value.clone(),
-                    sender,
-                );
-                self.browsing_context_script_command::<true>(cmd)?;
-            },
-            LocatorStrategy::LinkText | LocatorStrategy::PartialLinkText => {
-                let cmd = WebDriverScriptCommand::FindElementLinkText(
-                    parameters.value.clone(),
-                    parameters.using == LocatorStrategy::PartialLinkText,
-                    sender,
-                );
-                self.browsing_context_script_command::<true>(cmd)?;
-            },
-            LocatorStrategy::TagName => {
-                let cmd =
-                    WebDriverScriptCommand::FindElementTagName(parameters.value.clone(), sender);
-                self.browsing_context_script_command::<true>(cmd)?;
-            },
-            _ => {
-                return Err(WebDriverError::new(
-                    ErrorStatus::UnsupportedOperation,
-                    "Unsupported locator strategy",
-                ));
-            },
-        }
-
+        // Step 1 - 9.
+        let res = self.handle_find_elements(parameters)?;
         // Step 10. If result is empty, return error with error code no such element.
         // Otherwise, return the first element of result.
-        match wait_for_script_response(receiver)? {
-            Ok(value) => match value {
-                Some(value) => {
-                    let value_resp = serde_json::to_value(WebElement(value)).unwrap();
-                    Ok(WebDriverResponse::Generic(ValueResponse(value_resp)))
-                },
-                None => Err(WebDriverError::new(ErrorStatus::NoSuchElement, "")),
-            },
-            Err(error) => Err(WebDriverError::new(error, "")),
-        }
+        unwrap_first_element_response(res)
     }
 
     /// <https://w3c.github.io/webdriver/#close-window>
@@ -1234,62 +1192,16 @@ impl Handler {
     }
 
     /// <https://w3c.github.io/webdriver/#find-element-from-element>
-    fn handle_find_element_element(
+    fn handle_find_element_from_element(
         &self,
         element: &WebElement,
         parameters: &LocatorParameters,
     ) -> WebDriverResult<WebDriverResponse> {
-        // Step 4. If selector is undefined, return error with error code invalid argument.
-        if parameters.value.is_empty() {
-            return Err(WebDriverError::new(ErrorStatus::InvalidArgument, ""));
-        }
-        let (sender, receiver) = ipc::channel().unwrap();
-
-        match parameters.using {
-            LocatorStrategy::CSSSelector => {
-                let cmd = WebDriverScriptCommand::FindElementElementCSSSelector(
-                    parameters.value.clone(),
-                    element.to_string(),
-                    sender,
-                );
-                self.browsing_context_script_command::<true>(cmd)?;
-            },
-            LocatorStrategy::LinkText | LocatorStrategy::PartialLinkText => {
-                let cmd = WebDriverScriptCommand::FindElementElementLinkText(
-                    parameters.value.clone(),
-                    element.to_string(),
-                    parameters.using == LocatorStrategy::PartialLinkText,
-                    sender,
-                );
-                self.browsing_context_script_command::<true>(cmd)?;
-            },
-            LocatorStrategy::TagName => {
-                let cmd = WebDriverScriptCommand::FindElementElementTagName(
-                    parameters.value.clone(),
-                    element.to_string(),
-                    sender,
-                );
-                self.browsing_context_script_command::<true>(cmd)?;
-            },
-            _ => {
-                return Err(WebDriverError::new(
-                    ErrorStatus::UnsupportedOperation,
-                    "Unsupported locator strategy",
-                ));
-            },
-        }
+        // Step 1 - 8.
+        let res = self.handle_find_elements_from_element(element, parameters)?;
         // Step 9. If result is empty, return error with error code no such element.
         // Otherwise, return the first element of result.
-        match wait_for_script_response(receiver)? {
-            Ok(value) => match value {
-                Some(value) => {
-                    let value_resp = serde_json::to_value(WebElement(value))?;
-                    Ok(WebDriverResponse::Generic(ValueResponse(value_resp)))
-                },
-                None => Err(WebDriverError::new(ErrorStatus::NoSuchElement, "")),
-            },
-            Err(error) => Err(WebDriverError::new(error, "")),
-        }
+        unwrap_first_element_response(res)
     }
 
     /// <https://w3c.github.io/webdriver/#find-elements-from-element>
@@ -1418,22 +1330,11 @@ impl Handler {
         shadow_root: &ShadowRoot,
         parameters: &LocatorParameters,
     ) -> WebDriverResult<WebDriverResponse> {
+        // Step 1 - 8.
         let res = self.handle_find_elements_from_shadow_root(shadow_root, parameters)?;
         // Step 9. If result is empty, return error with error code no such element.
         // Otherwise, return the first element of result.
-        if let WebDriverResponse::Generic(ValueResponse(values)) = res {
-            let arr = values.as_array().unwrap();
-            if let Some(first) = arr.first() {
-                Ok(WebDriverResponse::Generic(ValueResponse(first.clone())))
-            } else {
-                Err(WebDriverError::new(ErrorStatus::NoSuchElement, ""))
-            }
-        } else {
-            Err(WebDriverError::new(
-                ErrorStatus::UnknownError,
-                "Unexpected response",
-            ))
-        }
+        unwrap_first_element_response(res)
     }
 
     fn handle_get_shadow_root(&self, element: WebElement) -> WebDriverResult<WebDriverResponse> {
@@ -2255,7 +2156,7 @@ impl WebDriverHandler<ServoExtensionRoute> for Handler {
             WebDriverCommand::FindElement(ref parameters) => self.handle_find_element(parameters),
             WebDriverCommand::FindElements(ref parameters) => self.handle_find_elements(parameters),
             WebDriverCommand::FindElementElement(ref element, ref parameters) => {
-                self.handle_find_element_element(element, parameters)
+                self.handle_find_element_from_element(element, parameters)
             },
             WebDriverCommand::FindElementElements(ref element, ref parameters) => {
                 self.handle_find_elements_from_element(element, parameters)
@@ -2380,3 +2281,16 @@ where
         .recv()
         .map_err(|_| WebDriverError::new(ErrorStatus::NoSuchWindow, ""))
 }
+
+fn unwrap_first_element_response(res: WebDriverResponse) -> WebDriverResult<WebDriverResponse> {
+    if let WebDriverResponse::Generic(ValueResponse(values)) = res {
+        let arr = values.as_array().unwrap();
+        if let Some(first) = arr.first() {
+            Ok(WebDriverResponse::Generic(ValueResponse(first.clone())))
+        } else {
+            Err(WebDriverError::new(ErrorStatus::NoSuchElement, ""))
+        }
+    } else {
+        unreachable!()
+    }
+}