Auto merge of #25515 - pshaughn:checkpoints, r=jdm

Add microtask checkpoints to script elements and custom elements

Servo had a microtask checkpoint at the end of running a script, but there was also supposed to be one at the end of HTML-parsing a script element before Javascript-parsing the script itself, and there were supposed to be checkpoints immediately after the call to a custom element constructor. This adds those, passing all cases of one WPT test file.

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `___` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #25016 except for the remaining not-really-about-microtasks case #25514

<!-- Either: -->
- [X] There are tests for these changes

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components/script/dom/customelementregistry.rs

@@ -20,6 +20,7 @@ use crate::dom::bindings::error::{
 use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::{Dom, DomRoot};
+use crate::dom::bindings::settings_stack::is_execution_stack_empty;
 use crate::dom::bindings::str::DOMString;
 use crate::dom::document::Document;
 use crate::dom::domexception::{DOMErrorName, DOMException};
@@ -543,6 +544,14 @@ impl CustomElementDefinition {
             }
         }
 
+        // https://heycam.github.io/webidl/#construct-a-callback-function
+        // https://html.spec.whatwg.org/multipage/#clean-up-after-running-script
+        if is_execution_stack_empty() {
+            window
+                .upcast::<GlobalScope>()
+                .perform_a_microtask_checkpoint();
+        }
+
         rooted!(in(*cx) let element_val = ObjectValue(element.get()));
         let element: DomRoot<Element> =
             match unsafe { DomRoot::from_jsval(*cx, element_val.handle(), ()) } {
@@ -690,6 +699,15 @@ fn run_upgrade_constructor(
         } {
             return Err(Error::JSFailed);
         }
+
+        // https://heycam.github.io/webidl/#construct-a-callback-function
+        // https://html.spec.whatwg.org/multipage/#clean-up-after-running-script
+        if is_execution_stack_empty() {
+            window
+                .upcast::<GlobalScope>()
+                .perform_a_microtask_checkpoint();
+        }
+
         // Step 8.3
         let mut same = false;
         rooted!(in(*cx) let construct_result_val = ObjectValue(construct_result.get()));

components/script/dom/htmlimageelement.rs

@@ -826,6 +826,8 @@ impl HTMLImageElement {
             // Step 8
             Some(data) => data,
             None => {
+                self.abort_request(State::Broken, ImageRequestPhase::Current);
+                self.abort_request(State::Broken, ImageRequestPhase::Pending);
                 // Step 9.
                 // FIXME(nox): Why are errors silenced here?
                 let _ = task_source.queue(
@@ -843,11 +845,6 @@ impl HTMLImageElement {
                         if src_present || Self::uses_srcset_or_picture(elem) {
                             this.upcast::<EventTarget>().fire_event(atom!("error"));
                         }
-                        // FIXME(nox): According to the spec, setting the current
-                        // request to the broken state is done prior to queuing a
-                        // task, why is this here?
-                        this.abort_request(State::Broken, ImageRequestPhase::Current);
-                        this.abort_request(State::Broken, ImageRequestPhase::Pending);
                     }),
                     window.upcast(),
                 );
@@ -864,6 +861,8 @@ impl HTMLImageElement {
                 self.prepare_image_request(&url, &src, pixel_density);
             },
             Err(_) => {
+                self.abort_request(State::Broken, ImageRequestPhase::Current);
+                self.abort_request(State::Broken, ImageRequestPhase::Pending);
                 // Step 12.1-12.5.
                 let src = src.0;
                 // FIXME(nox): Why are errors silenced here?
@@ -877,11 +876,6 @@ impl HTMLImageElement {
                         }
                         this.upcast::<EventTarget>().fire_event(atom!("error"));
 
-                        // FIXME(nox): According to the spec, setting the current
-                        // request to the broken state is done prior to queuing a
-                        // task, why is this here?
-                        this.abort_request(State::Broken, ImageRequestPhase::Current);
-                        this.abort_request(State::Broken, ImageRequestPhase::Pending);
                     }),
                     window.upcast(),
                 );

components/script/dom/servoparser/mod.rs

@@ -558,6 +558,19 @@ impl ServoParser {
                 Err(script) => script,
             };
 
+            // https://html.spec.whatwg.org/multipage/#parsing-main-incdata
+            // branch "An end tag whose tag name is "script"
+            // The spec says to perform the microtask checkpoint before
+            // setting the insertion mode back from Text, but this is not
+            // possible with the way servo and html5ever currently
+            // relate to each other, and hopefully it is not observable.
+            if is_execution_stack_empty() {
+                self.document
+                    .window()
+                    .upcast::<GlobalScope>()
+                    .perform_a_microtask_checkpoint();
+            }
+
             let script_nesting_level = self.script_nesting_level.get();
 
             self.script_nesting_level.set(script_nesting_level + 1);

components/script/microtask.rs

@@ -90,6 +90,8 @@ impl MicrotaskQueue {
         // Step 1
         self.performing_a_microtask_checkpoint.set(true);
 
+        debug!("Now performing a microtask checkpoint");
+
         // Steps 2
         while !self.microtask_queue.borrow().is_empty() {
             rooted_vec!(let mut pending_queue);

tests/wpt/metadata/custom-elements/microtasks-and-constructors.html.ini

@@ -1,10 +0,0 @@
-[microtasks-and-constructors.html]
-  [Microtasks evaluate immediately when the stack is empty inside the parser]
-    expected: FAIL
-
-  [Microtasks evaluate immediately when the stack is empty inside the parser, causing the checks on no attributes to fail]
-    expected: FAIL
-
-  [Microtasks evaluate afterward when the stack is not empty using createElement()]
-    expected: FAIL
-

tests/wpt/metadata/dom/nodes/MutationObserver-document.html.ini

@@ -1,11 +0,0 @@
-[MutationObserver-document.html]
-  type: testharness
-  [parser insertion mutations]
-    expected: FAIL
-
-  [parser script insertion mutation]
-    expected: FAIL
-
-  [removal of parent during parsing]
-    expected: FAIL
-