script: Add custom logging representation for DOM interfaces. (#35416)

Signed-off-by: Josh Matthews <josh@joshmatthews.net>

components/script/dom/console.rs

@@ -3,19 +3,23 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use std::convert::TryFrom;
-use std::{io, ptr};
+use std::ptr::{self, NonNull};
+use std::{io, slice};
 
 use devtools_traits::{
     ConsoleMessage, ConsoleMessageArgument, ConsoleMessageBuilder, LogLevel,
     ScriptToDevtoolsControlMsg, StackFrame,
 };
 use js::jsapi::{self, ESClass, PropertyDescriptor};
-use js::jsval::UndefinedValue;
+use js::jsval::{Int32Value, UndefinedValue};
 use js::rust::wrappers::{
     GetBuiltinClass, GetPropertyKeys, JS_GetOwnPropertyDescriptorById, JS_GetPropertyById,
-    JS_IdToValue, JS_ValueToSource,
+    JS_IdToValue, JS_Stringify, JS_ValueToSource,
 };
-use js::rust::{describe_scripted_caller, CapturedJSStack, HandleValue, IdVector};
+use js::rust::{
+    describe_scripted_caller, CapturedJSStack, HandleObject, HandleValue, IdVector, ToString,
+};
+use script_bindings::conversions::get_dom_class;
 
 use crate::dom::bindings::codegen::Bindings::ConsoleBinding::consoleMethods;
 use crate::dom::bindings::conversions::jsstring_to_str;
@@ -147,10 +151,10 @@ fn console_argument_from_handle_value(
 
 #[allow(unsafe_code)]
 fn stringify_handle_value(message: HandleValue) -> DOMString {
-    let cx = *GlobalScope::get_cx();
+    let cx = GlobalScope::get_cx();
     unsafe {
         if message.is_string() {
-            return jsstring_to_str(cx, std::ptr::NonNull::new(message.to_string()).unwrap());
+            return jsstring_to_str(*cx, std::ptr::NonNull::new(message.to_string()).unwrap());
         }
         unsafe fn stringify_object_from_handle_value(
             cx: *mut jsapi::JSContext,
@@ -213,7 +217,8 @@ fn stringify_handle_value(message: HandleValue) -> DOMString {
                         explicit_keys = false;
                     }
                 }
-                let value_string = stringify_inner(cx, property.handle(), parents.clone());
+                let value_string =
+                    stringify_inner(JSContext::from_ptr(cx), property.handle(), parents.clone());
                 if explicit_keys {
                     let key = if id.is_string() || id.is_symbol() || id.is_int() {
                         rooted!(in(cx) let mut key_value = UndefinedValue());
@@ -239,11 +244,7 @@ fn stringify_handle_value(message: HandleValue) -> DOMString {
                 DOMString::from(format!("{{{}}}", itertools::join(props, ", ")))
             }
         }
-        unsafe fn stringify_inner(
-            cx: *mut jsapi::JSContext,
-            value: HandleValue,
-            mut parents: Vec<u64>,
-        ) -> DOMString {
+        fn stringify_inner(cx: JSContext, value: HandleValue, mut parents: Vec<u64>) -> DOMString {
             if parents.len() >= MAX_LOG_DEPTH {
                 return DOMString::from("...");
             }
@@ -255,15 +256,73 @@ fn stringify_handle_value(message: HandleValue) -> DOMString {
                 // This produces a better value than "(void 0)" from JS_ValueToSource.
                 return DOMString::from("undefined");
             } else if !value.is_object() {
-                return handle_value_to_string(cx, value);
+                return unsafe { handle_value_to_string(*cx, value) };
             }
             parents.push(value_bits);
-            stringify_object_from_handle_value(cx, value, parents)
+
+            if value.is_object() {
+                if let Some(repr) = maybe_stringify_dom_object(cx, value) {
+                    return repr;
+                }
+            }
+            unsafe { stringify_object_from_handle_value(*cx, value, parents) }
         }
         stringify_inner(cx, message, Vec::new())
     }
 }
 
+#[allow(unsafe_code)]
+fn maybe_stringify_dom_object(cx: JSContext, value: HandleValue) -> Option<DOMString> {
+    // The standard object serialization is not effective for DOM objects,
+    // since their properties generally live on the prototype object.
+    // Instead, fall back to the output of JSON.stringify combined
+    // with the class name extracted from the output of toString().
+    rooted!(in(*cx) let obj = value.to_object());
+    let is_dom_class = unsafe { get_dom_class(obj.get()).is_ok() };
+    if !is_dom_class {
+        return None;
+    }
+    rooted!(in(*cx) let class_name = unsafe { ToString(*cx, value) });
+    let Some(class_name) = NonNull::new(class_name.get()) else {
+        return Some("<error converting DOM object to string>".into());
+    };
+    let class_name = unsafe {
+        jsstring_to_str(*cx, class_name)
+            .replace("[object ", "")
+            .replace("]", "")
+    };
+    let mut repr = format!("{} ", class_name);
+    rooted!(in(*cx) let mut value = value.get());
+
+    #[allow(unsafe_code)]
+    unsafe extern "C" fn stringified(
+        string: *const u16,
+        len: u32,
+        data: *mut std::ffi::c_void,
+    ) -> bool {
+        let s = data as *mut String;
+        let string_chars = slice::from_raw_parts(string, len as usize);
+        (*s).push_str(&String::from_utf16_lossy(string_chars));
+        true
+    }
+
+    rooted!(in(*cx) let space = Int32Value(2));
+    let stringify_result = unsafe {
+        JS_Stringify(
+            *cx,
+            value.handle_mut(),
+            HandleObject::null(),
+            space.handle(),
+            Some(stringified),
+            &mut repr as *mut String as *mut _,
+        )
+    };
+    if !stringify_result {
+        return Some("<error converting DOM object to string>".into());
+    }
+    Some(repr.into())
+}
+
 fn stringify_handle_values(messages: &[HandleValue]) -> DOMString {
     DOMString::from(itertools::join(
         messages.iter().copied().map(stringify_handle_value),