script: fix worklet implementation to fetch modules instead of classic scripts by niyabits · Pull Request #46856 · servo/servo

niyabits · 2026-07-29T07:48:12Z

Fix the existing Worklet implementation by adding the necessary infrastructure for fetching modules (e.g., implementing task manager on Worklet) and using our implementation of fetch a worklet/module worker script graph instead of fetching classic scripts using load_whole_resource.

Testing: Tests in tests/wpt/mozilla/tests/mozilla/worklets already cover the changes, some fixes were made to comply with the specs.

Fixes: #45306

mukilan

There are some lint failures because of spec link formats being different. You can follow the suggestion in the lint and replace it with the one in the message.
Also there are some long spec comments in the code that need to be reformatted to span multiple lines.

Taym95 · 2026-08-02T10:52:10Z

+  // global object to perform the following steps:
+  // 6.4.5.1 If pendingTasks is not −1:
+  // 6.4.5.1.1 Set pendingTasks to pendingTasks − 1.
+  // 6.4.5.1.2 If pendingTasks is 0, then resolve promise.


why spec in test ?

It's part of this note above:

// NOTE: The specification for AddModule does not use the promise returned by "run a module script",
// therefore an exception thrown when executing a module will not be propagated.
// <https://html.spec.whatwg.org/multipage/#dom-worklet-addmodule

It feels unintuitive that addModule will resolve the promise even when there is a syntax error while loading a module.

I think I initially added the steps to serve as extra context to explain the behavior the specification expects. Although looking back at it, I think maybe mentioning the step number in the NOTE comment maybe sufficient.

Relevant issue: w3c/css-houdini-drafts#407

@Taym95 I think the issue I referenced above was closed accidentally and the specification might change in the future. So it might be good to know what the spec said to justify the test in the future.

Are you okay with the steps?

Signed-off-by: Niya <niyabits@disroot.org>

…k_manager Signed-off-by: Niya <niyabits@disroot.org>

Signed-off-by: Niya <niyabits@disroot.org>

mukilan · 2026-08-05T06:46:24Z

+        // Step 6. Run the following steps in parallel:
+        // Step 6.1. If workletInstance's global scopes is empty:
+        // Step 6.1.1. Create a worklet global scope given workletInstance.
        let global_scope = self.window.as_global_scope();


The steps are still attached to this line, which makes them seem like they are related. You probably separate them by blank line and also add a note after the steps that they are implemented in those other functions. The comment block should probably include steps 6.1.2 and 6.1.3 below.

Signed-off-by: Niya <niyabits@disroot.org>

niyabits · 2026-08-05T07:39:04Z

I have moved the steps Step 6.1.2. and Step 6.1.3. above here,

        let global_scope = self.window.as_global_scope();

As I don't think there is a good reason to keep the steps after that line.

I have added a note for the steps as well:

        // Step 5. Let workletInstance be this.

        // Step 6. Run the following steps in parallel:
        // Step 6.1. If workletInstance's global scopes is empty:
        // Step 6.1.1. Create a worklet global scope given workletInstance.
        // Step 6.1.2. Optionally, create additional global scope instances given workletInstance, depending on the specific worklet in question and its specification.
        // Step 6.1.3. Wait for all steps of the creation process(es) — including those taking place within the worklet agents — to complete, before moving on.
        // NOTE: Step 6 is implemented by WorkletThread's run method.
        // Step 6.1, Step 6.1.1, and Step 6.1.3 are implemented in the `get_worklet_global_scope` method.

        let global_scope = self.window.as_global_scope();

I believe I do not need a longer explanation for the steps.

edit: I have removed space between each individual step.

Signed-off-by: Niya <niyabits@disroot.org>

…c scripts (servo#46856) Fix the existing Worklet implementation by adding the necessary infrastructure for fetching modules (e.g., implementing task manager on Worklet) and using our implementation of `fetch a worklet/module worker script graph` instead of fetching classic scripts using `load_whole_resource`. Testing: Tests in `tests/wpt/mozilla/tests/mozilla/worklets` already cover the changes, some fixes were made to comply with the specs. Fixes: servo#45306 --------- Signed-off-by: Niya <niyabits@disroot.org>

niyabits requested a review from gterzian as a code owner July 29, 2026 07:48

servo-highfive added the S-awaiting-review There is new code that needs to be reviewed. label Jul 29, 2026

niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch from e8d9ba6 to 6b53081 Compare July 29, 2026 07:52

jdm reviewed Jul 29, 2026

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Comment thread components/script/dom/worklet/worklet.rs Outdated

mukilan reviewed Jul 29, 2026

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eerii reviewed Jul 29, 2026

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Comment thread components/script/dom/worklet/worklet.rs Outdated

Comment thread components/script/dom/worklet/worklet.rs Outdated

Comment thread components/script/dom/worklet/worklet.rs Outdated

eerii reviewed Jul 29, 2026

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Comment thread components/script/dom/worklet/worklet.rs Outdated

mukilan reviewed Jul 30, 2026

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niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch 10 times, most recently from 9448a32 to ffe3180 Compare August 2, 2026 06:33

Taym95 reviewed Aug 2, 2026

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niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch from ffe3180 to 91e5363 Compare August 3, 2026 14:29

niyabits requested a review from Taym95 August 3, 2026 14:30

niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch from 91e5363 to e05bc6c Compare August 4, 2026 11:45

niyabits added 8 commits August 5, 2026 11:52

script(wip): change addModule to fetch JS modules

22bd47e

Signed-off-by: Niya <niyabits@disroot.org>

script(wip): rebase main

1539743

Signed-off-by: Niya <niyabits@disroot.org>

script: implement task manager on workletglobalscope

6a6d7f6

Signed-off-by: Niya <niyabits@disroot.org>

script: allow downcasting globalscope to worklet when getting the tas…

7502bb8

…k_manager Signed-off-by: Niya <niyabits@disroot.org>

script(wip): try adding microtask queue

f6a786e

Signed-off-by: Niya <niyabits@disroot.org>

fix(script): fetch modules instead of classic scripts for worklets

5292722

Signed-off-by: Niya <niyabits@disroot.org>

script: cleanup and add docs comments

15823ff

Signed-off-by: Niya <niyabits@disroot.org>

script: ignore clippy lint warnings for too many args

c3ae0db

Signed-off-by: Niya <niyabits@disroot.org>

niyabits added 5 commits August 5, 2026 11:52

script: add comments referencing specs and other minor fixes

ab110ad

Signed-off-by: Niya <niyabits@disroot.org>

script: improve/fix error messages and spec comments

84cedb8

Signed-off-by: Niya <niyabits@disroot.org>

script: propogate errors, improve comments

770ed69

Signed-off-by: Niya <niyabits@disroot.org>

script: fix lint errors, update wpt manifest

a0bafb0

Signed-off-by: Niya <niyabits@disroot.org>

fix: remove .DS_Store from MANIFEST.json

eeba2ee

Signed-off-by: Niya <niyabits@disroot.org>

niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch from e05bc6c to eeba2ee Compare August 5, 2026 06:22

mukilan reviewed Aug 5, 2026

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Comment thread components/script/dom/worklet/worklet.rs Outdated

fix: improve comments for steps

5a58504

Signed-off-by: Niya <niyabits@disroot.org>

niyabits requested a review from mukilan August 5, 2026 08:02

niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch 2 times, most recently from 9625f66 to 25c4583 Compare August 5, 2026 09:58

refactor: use values instead of iter when getting global scope values

1ee5753

Signed-off-by: Niya <niyabits@disroot.org>

niyabits force-pushed the script/implement-task-manager-on-worklet-global-scope branch from 25c4583 to 1ee5753 Compare August 5, 2026 10:08

mukilan approved these changes Aug 5, 2026

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servo-highfive removed the S-awaiting-review There is new code that needs to be reviewed. label Aug 5, 2026

mukilan added this pull request to the merge queue Aug 5, 2026

servo-highfive added the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Aug 5, 2026

Merged via the queue into servo:main with commit 086a3d6 Aug 5, 2026
33 checks passed

servo-highfive removed the S-awaiting-merge The PR is in the process of compiling and running tests on the automated CI. label Aug 5, 2026

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niyabits commented Jul 29, 2026

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niyabits commented Aug 5, 2026 •

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