Use strum to iterate through enum variants and get their names (#35933)

`strum` allows us to avoid manually listing enum variant names and also
to get their names as static strings. We cannot use this for all cases
due to https://github.com/Peternator7/strum/issues/152, but we can
still use it to remove a lot of code.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>

components/script/Cargo.toml

@@ -113,6 +113,8 @@ servo_url = { path = "../url" }
 smallvec = { workspace = true, features = ["union"] }
 style_malloc_size_of = { workspace = true }
 glow = { workspace = true }
+strum = { workspace = true }
+strum_macros = { workspace = true }
 style = { workspace = true }
 stylo_dom = { workspace = true }
 style_traits = { workspace = true }

components/script/task_manager.rs

@@ -8,6 +8,7 @@ use std::cell::Ref;
 use std::collections::HashMap;
 
 use base::id::PipelineId;
+use strum::VariantArray;
 
 use crate::messaging::ScriptEventLoopSender;
 use crate::task::TaskCanceller;
@@ -36,7 +37,7 @@ impl TaskCancellers {
             Self::OnePerTaskSource(..) => {
                 // We must create the canceller if they aren't created because we want future
                 // tasks to be ignored completely.
-                for task_source_name in TaskSourceName::all() {
+                for task_source_name in TaskSourceName::VARIANTS.iter() {
                     self.get(*task_source_name)
                         .cancelled
                         .store(true, Ordering::SeqCst)

components/script/task_queue.rs

@@ -10,6 +10,7 @@ use std::default::Default;
 
 use base::id::PipelineId;
 use crossbeam_channel::{self, Receiver, Sender};
+use strum::VariantArray;
 
 use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::worker::TrustedWorkerAddress;
@@ -211,8 +212,7 @@ impl<T: QueuedTaskConversion> TaskQueue<T> {
         self.process_incoming_tasks(first_msg, &fully_active);
         let mut throttled = self.throttled.borrow_mut();
         let mut throttled_length: usize = throttled.values().map(|queue| queue.len()).sum();
-        let task_source_names = TaskSourceName::all();
-        let mut task_source_cycler = task_source_names.iter().cycle();
+        let mut task_source_cycler = TaskSourceName::VARIANTS.iter().cycle();
         // "being busy", is defined as having more than x tasks for this loop's iteration.
         // As long as we're not busy, and there are throttled tasks left:
         loop {

components/script/task_source.rs

@@ -6,6 +6,7 @@ use std::fmt;
 
 use base::id::PipelineId;
 use malloc_size_of_derive::MallocSizeOf;
+use strum_macros::VariantArray;
 use stylo_atoms::Atom;
 
 use crate::dom::bindings::refcounted::Trusted;
@@ -19,10 +20,7 @@ use crate::task_manager::TaskManager;
 /// The names of all task sources, used to differentiate TaskCancellers. Note: When adding a task
 /// source, update this enum. Note: The HistoryTraversalTaskSource is not part of this, because it
 /// doesn't implement TaskSource.
-///
-/// Note: When adding or removing a [`TaskSourceName`], be sure to also update the return value of
-/// [`TaskSourceName::all`].
-#[derive(Clone, Copy, Debug, Eq, Hash, JSTraceable, MallocSizeOf, PartialEq)]
+#[derive(Clone, Copy, Debug, Eq, Hash, JSTraceable, MallocSizeOf, PartialEq, VariantArray)]
 pub(crate) enum TaskSourceName {
     Canvas,
     DOMManipulation,
@@ -68,28 +66,6 @@ impl From<TaskSourceName> for ScriptThreadEventCategory {
     }
 }
 
-impl TaskSourceName {
-    pub(crate) fn all() -> &'static [TaskSourceName] {
-        &[
-            TaskSourceName::Canvas,
-            TaskSourceName::DOMManipulation,
-            TaskSourceName::FileReading,
-            TaskSourceName::FontLoading,
-            TaskSourceName::HistoryTraversal,
-            TaskSourceName::Networking,
-            TaskSourceName::PerformanceTimeline,
-            TaskSourceName::PortMessage,
-            TaskSourceName::UserInteraction,
-            TaskSourceName::RemoteEvent,
-            TaskSourceName::Rendering,
-            TaskSourceName::MediaElement,
-            TaskSourceName::WebSocket,
-            TaskSourceName::Timer,
-            TaskSourceName::Gamepad,
-        ]
-    }
-}
-
 pub(crate) struct TaskSource<'task_manager> {
     pub(crate) task_manager: &'task_manager TaskManager,
     pub(crate) name: TaskSourceName,