feat: makes it optional whether to parse runes.

[ota-meshi]

related to #423

This PR changes the parser to allow opt-in/out of Rune parsing. (However, it requires Svelte v5.)

The main changes are:

• Added a new option svelteFeatures.runes to control whether runes are parsed.
• Added a new option parserOptions.svelteConfig to specify svelte.config.js.
  If not specified, some config will be statically parsed from the svelte.config.js file.
• If there is no option in svelteFeatures.runes, it will read the compilerOptions.runes in svelte.config.js.
• If <svelte:options runes={...}> is present, it determines whether to prioritize them and parse Runes.
• Change the parser service to provide svelteParseContext, to make that information available to the eslint-plugin.
  • I think the next issue can be solved by telling the compiler whether it should parse in rune mode.
    • $page is an illegal variable name eslint-plugin-svelte#652

[changeset-bot]

🦋 Changeset detected

Latest commit: baf724a

The changes in this PR will be included in the next version bump.

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Name	Type
svelte-eslint-parser	Minor

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[coveralls]

Pull Request Test Coverage Report for Build 9534250043

Details

• 160 of 163 (98.16%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 91.501%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/globals.ts	7	8	87.5%
src/svelte-config/parser.ts	78	80	97.5%

Totals
Change from base Build 9529150497:	0.1%
Covered Lines:	2949
Relevant Lines:	3131

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9534267800

Details

• 160 of 163 (98.16%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 91.501%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/globals.ts	7	8	87.5%
src/svelte-config/parser.ts	78	80	97.5%

Totals
Change from base Build 9529150497:	0.1%
Covered Lines:	2949
Relevant Lines:	3131

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9534824834

Details

• 160 of 163 (98.16%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 91.482%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/globals.ts	7	8	87.5%
src/svelte-config/parser.ts	78	80	97.5%

Totals
Change from base Build 9529150497:	0.1%
Covered Lines:	2949
Relevant Lines:	3131

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9540091489

Details

• 196 of 215 (91.16%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.5%) to 90.864%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/globals.ts	7	8	87.5%
src/scope/index.ts	5	7	71.43%
src/svelte-config/parser.ts	116	132	87.88%

Totals
Change from base Build 9529150497:	-0.5%
Covered Lines:	2985
Relevant Lines:	3183

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💛 - Coveralls

[ota-meshi]

I realized that it would be better to have svelte.config.js specified in eslint.config.js rather than statically analyzing svelte.config.js. I will make that change.

Done

[coveralls]

Pull Request Test Coverage Report for Build 9541551900

Details

• 207 of 236 (87.71%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.0%) to 90.411%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/globals.ts	7	8	87.5%
src/scope/index.ts	5	7	71.43%
src/svelte-config/parser.ts	125	151	82.78%

Totals
Change from base Build 9529150497:	-1.0%
Covered Lines:	2996
Relevant Lines:	3204

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9541685261

Details

• 207 of 236 (87.71%) changed or added relevant lines in 10 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.0%) to 90.411%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/parser/globals.ts	7	8	87.5%
src/scope/index.ts	5	7	71.43%
src/svelte-config/parser.ts	125	151	82.78%

Totals
Change from base Build 9529150497:	-1.0%
Covered Lines:	2996
Relevant Lines:	3204

---

💛 - Coveralls

[baseballyama]

I have a question.

Both runes mode and legacy mode can use store right?
Can you tell me more details why this PR can solve below?

• $page is an illegal variable name eslint-plugin-svelte#652

https://svelte-5-preview.vercel.app/#H4sIAAAAAAAAE2VR227DIAz9FQtNaqJGvbymSaR9x9hDSsjElhgEptuE-PcJ0iaV9mRzjo3tcwIb1SQdq98Cw36WrGavxrCK0a9JD3eTE0lWMae9FQlpnLDKUMeRk5qNtgQBTP8hIcJo9Qy7w9GRtnJ3SSWTJBDaI0ELL456ksWpTAxyGj0KUhpBobBylkhFCSExnNKPB2-G1FBgCW33YDhZSd7i9uY09NTXgIcUYQ_nBxMvSxbLe7Kssm_hnIHIsTluB2EzqFuXa2oIOcbmmLA7lbaqIbzk7dKwjb56Io2gUUxKfLVhvSlmqTLq0rilsGMVm_WgRiUHVpP1MlarBVm_zYRP92zAKvq3VdRfp034xawn9VH-5Fqh0dFiUru2FQEW2U6Q5fm_0Hv8A7R7ehQfAgAA

[baseballyama]

Added a new option parserOptions.svelteConfig to specify svelte.config.js.

This is just my opinion but, in 99% of cases, compilerOptions.runs is defined statically in svelte.config.js.
So I think it's enough to parse svelte.config.js statically by default.
And we will use svelteFeatures.runes only if the value is explicitly specified in eslint config.

[ota-meshi]

Hmm... I guess I misunderstood something.
This PR doesn't solve sveltejs/eslint-plugin-svelte#652.
I thought that telling the compiler the runes mode correctly would solve the problem, but it didn't 😓

[ota-meshi]

This is just my opinion but, in 99% of cases, compilerOptions.runs is defined statically in svelte.config.js.
So I think it's enough to parse svelte.config.js statically by default.
And we will use svelteFeatures.runes only if the value is explicitly specified in eslint config.

You are right about the compilerOptions.runs.
However, we think that in the future we might want to access more than just compilerOptions.runs, so I thought it made sense to add this option now.

For example, the following issue in eslint-plugin-svelte can be easily resolved if we have access to onwarn.

sveltejs/eslint-plugin-svelte#311

For example, we can get the correct routes information even without the following settings:

https://sveltejs.github.io/eslint-plugin-svelte/user-guide/#settings-svelte-kit

Currently, the parser does not use any information other than compilerOptions.runs. However, I think that in the future it may.
Also we can also use it from parserServices to share svelte.config.js information with eslint-plugin rules.

[baseballyama]

However, we think that in the future we might want to access more than just compilerOptions.runs, so I thought it made sense to add this option now.

Agreed!

How about mimic the logic with vite-plugin-svelte?
https://github.com/sveltejs/vite-plugin-svelte/blob/main/docs/config.md#config-file

As default, user don't need to configure parserOptions.svelteConfig but automatically read the file.
If user use special file name, then user can configure parserOptions.svelteConfig or configure svelteFeatures .xxx as inline option.

It would be convenient for users if fewer settings could be made.
And svelte users may easier to understand if there are similar rules across the Svelte ecosystem.

[ota-meshi]

As default, user don't need to configure parserOptions.svelteConfig but automatically read the file.

Unfortunately, currently the eslint custom parser cannot load ESMs because it needs to run synchronously, so svelte.config.js cannot be loaded inside the parser.

See eslint/eslint#15475

[baseballyama]

Ah I forgot this😅.

[baseballyama]

Nice!

[ota-meshi]

@baseballyama
With this change, we might still be missing some features 😓

I have a question. Will the Svelte core compiler automatically parse runes as runes when they are used, even without compilerOptions.runes?
If so, this parser needs to be handled the same way.

[baseballyama]

Ahh, yeah, you are right.
If there is rune symbol in .svelte / .svelte.js file, compiler will automatically enable rune mode for the component.
If compilerOptions.runes is true, apply rune mode compulsorily. (So we can not use export let xxx anymore.)
If compilerOptions.runes is false, the compiler doesn't use runes. (So if there is $derived or some runes, $derived will be behave as normal variable.)

[baseballyama]

I'm fixing.