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Merged
jasonlyu123 merged 21 commits into from
May 5, 2026
Merged

feat: typescript 6.0 support #2985

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e433559
wip
jasonlyu123 Feb 13, 2026
026cd33
Merge branch 'master' of https://github.com/sveltejs/language-tools i…
jasonlyu123 Mar 24, 2026
7e093ce
bumps
jasonlyu123 Mar 24, 2026
83f3ec2
another default change
jasonlyu123 Mar 24, 2026
9bc6cff
changeset
jasonlyu123 Mar 24, 2026
2c578bb
format
jasonlyu123 Mar 24, 2026
120ca56
fix svelte2tsx build for now
jasonlyu123 Mar 24, 2026
41bef87
more svelte2tsx migrate
jasonlyu123 Mar 24, 2026
c9b0987
add node to be explicit
jasonlyu123 Mar 24, 2026
02eadea
avoid svelteHTML.mapElementTag in perf test for now
jasonlyu123 Mar 25, 2026
4209e42
update svelte5 snapshot
jasonlyu123 Mar 25, 2026
e689a42
update svelte-check smoke test to bundler
jasonlyu123 Mar 25, 2026
c1fed4f
Merge branch 'master' of https://github.com/sveltejs/language-tools i…
jasonlyu123 Mar 26, 2026
9199b47
try fix flaky test
jasonlyu123 Mar 27, 2026
36742a6
Merge branch 'master' of https://github.com/sveltejs/language-tools i…
jasonlyu123 Mar 31, 2026
b224592
move typescript to peer in language server
jasonlyu123 Apr 2, 2026
24d9421
Merge branch 'master' of https://github.com/sveltejs/language-tools i…
jasonlyu123 Apr 10, 2026
c003ae9
another drive-by fix
jasonlyu123 Apr 10, 2026
7a659b1
Merge branch 'master' of https://github.com/sveltejs/language-tools i…
jasonlyu123 Apr 30, 2026
7d232bc
use 6.0.3
jasonlyu123 Apr 30, 2026
0f1ce0b
Merge branch 'ts-6.0' of https://github.com/jasonlyu123/language-tool…
jasonlyu123 May 5, 2026
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7 changes: 7 additions & 0 deletions .changeset/calm-birds-show.md
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@@ -0,0 +1,7 @@
---
'svelte-language-server': patch
'svelte-check': patch
'svelte2tsx': patch
---

feat: typescript 6.0 support
2 changes: 1 addition & 1 deletion package.json
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Expand Up @@ -15,7 +15,7 @@
"changeset:publish": "changeset publish"
},
"dependencies": {
"typescript": "^5.9.2"
"typescript": "^6.0.2"
},
"devDependencies": {
"@changesets/cli": "^2.29.7",
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2 changes: 1 addition & 1 deletion packages/language-server/package.json
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Expand Up @@ -62,7 +62,7 @@
"prettier-plugin-svelte": "^3.5.0",
"svelte": "^4.2.19",
"svelte2tsx": "workspace:~",
"typescript": "^5.9.2",
"typescript": "^5.9.2 || ^6.0.2",
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@teemingc teemingc Mar 24, 2026 •
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I'm not sure if the || syntax works here. Is the intention to provide support for both? It might be better to specify this as a peerDep instead 🤔 though I'm not sure how that works with VS Code extensions

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@jasonlyu123 jasonlyu123 Mar 24, 2026

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Yeah, it's meant to support both. I tested by installing a git repository, and it seems to be working as I intended: By default, it installs 6.0 and can be manually overridden to be 5.9. I think we can also move it to peerDep and mark it a breaking change?

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@dummdidumm dummdidumm Apr 2, 2026

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peer dep sounds good, though we gotta do language-server package as a minor then

"typescript-auto-import-cache": "^0.3.6",
"vscode-css-languageservice": "~6.3.5",
"vscode-html-languageservice": "~5.4.0",
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34 changes: 34 additions & 0 deletions packages/language-server/src/ambient.d.ts
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@@ -0,0 +1,34 @@
declare module 'estree-walker' {
export function walk(
ast: import('estree').BaseNode,
{
enter,
leave
}: {
enter?: (
this: {
skip: () => void;
remove: () => void;
replace: (node: import('estree').BaseNode) => void;
},
node: import('estree').BaseNode,
parent: import('estree').BaseNode,
key: string,
index: number
) => void;
leave?: (
this: {
skip: () => void;
remove: () => void;
replace: (node: import('estree').BaseNode) => void;
},
node: import('estree').BaseNode,
parent: import('estree').BaseNode,
key: string,
index: number
) => void;
}
): import('estree').BaseNode;

export type BaseNode = import('estree').BaseNode;
}
7 changes: 6 additions & 1 deletion packages/language-server/src/plugins/typescript/serviceCache.ts
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Expand Up @@ -71,7 +71,12 @@ export function createProject(
return undefined;
}

const factory = minor < 3 ? createProject50 : minor < 5 ? createProject53 : createProject55;
const factory =
major === 5 && minor < 3
? createProject50
: major === 5 && minor < 5
? createProject53
: createProject55;
const project = factory(ts, host, createLanguageService, options);

const proxyMethods: (keyof typeof project)[] = [
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6 changes: 3 additions & 3 deletions ...er/test/plugins/typescript/features/diagnostics/fixtures/bind-this/expected_svelte_4.json
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Expand Up @@ -36,7 +36,7 @@
},
"severity": 1,
"source": "ts",
"message": "Type 'Component' is not assignable to type 'OtherComponent'.\n Type '{ prop: boolean; }' is not assignable to type '{ prop: string; }'.\n Types of property 'prop' are incompatible.\n Type 'boolean' is not assignable to type 'string'.",
"message": "Type 'Component' is not assignable to type 'OtherComponent'.\n The types of '$$prop_def.prop' are incompatible between these types.\n Type 'boolean' is not assignable to type 'string'.",
"code": 2322,
"tags": []
},
Expand Down Expand Up @@ -69,7 +69,7 @@
},
"severity": 1,
"source": "ts",
"message": "Type 'Component' is not assignable to type 'OtherComponent'.\n Type '{ prop: boolean; }' is not assignable to type '{ prop: string; }'.\n Types of property 'prop' are incompatible.\n Type 'boolean' is not assignable to type 'string'.",
"message": "Type 'Component' is not assignable to type 'OtherComponent'.\n The types of '$$prop_def.prop' are incompatible between these types.\n Type 'boolean' is not assignable to type 'string'.",
"code": 2322,
"tags": []
},
Expand All @@ -80,7 +80,7 @@
},
"severity": 1,
"source": "ts",
"message": "Type 'ComponentWithGeneric<boolean>' is not assignable to type 'ComponentWithGeneric<string>'.\n Type 'boolean' is not assignable to type 'string'.",
"message": "Type 'ComponentWithGeneric<boolean>' is not assignable to type 'ComponentWithGeneric<string>'.\n The types of '$$prop_def.prop' are incompatible between these types.\n Type 'boolean' is not assignable to type 'string'.",
"code": 2322,
"tags": []
},
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1 change: 1 addition & 0 deletions ...rver/test/plugins/typescript/features/diagnostics/fixtures/checkjs-nostrict/tsconfig.json
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@@ -1,6 +1,7 @@
{
"compilerOptions": {
"checkJs": true,
"strict": false,
/**
This is actually not needed, but makes the tests faster
because TS does not look up other types.
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1 change: 1 addition & 0 deletions ...e-server/test/plugins/typescript/features/diagnostics/fixtures/custom-types/tsconfig.json
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@@ -1,5 +1,6 @@
{
"compilerOptions": {
"strict": false,
/**
This is actually not needed, but makes the tests faster
because TS does not look up other types.
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4 changes: 2 additions & 2 deletions ...er/test/plugins/typescript/features/inlayHints/fixtures/component-handler/expectedv2.json
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Expand Up @@ -12,8 +12,8 @@
"value": "MouseEvent",
"location": {
"range": {
"start": { "line": 20928, "character": 10 },
"end": { "line": 20928, "character": 20 }
"start": { "line": 25013, "character": 10 },
"end": { "line": 25013, "character": 20 }
},
"uri": "<node_modules>/typescript/lib/lib.dom.d.ts"
}
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12 changes: 6 additions & 6 deletions ...rver/test/plugins/typescript/features/inlayHints/fixtures/element-handler/expectedv2.json
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Expand Up @@ -6,8 +6,8 @@
"value": "MouseEvent",
"location": {
"range": {
"start": { "line": 20928, "character": 10 },
"end": { "line": 20928, "character": 20 }
"start": { "line": 25013, "character": 10 },
"end": { "line": 25013, "character": 20 }
},
"uri": "<node_modules>/typescript/lib/lib.dom.d.ts"
}
Expand All @@ -21,8 +21,8 @@
"value": "EventTarget",
"location": {
"range": {
"start": { "line": 11562, "character": 10 },
"end": { "line": 11562, "character": 21 }
"start": { "line": 14373, "character": 10 },
"end": { "line": 14373, "character": 21 }
},
"uri": "<node_modules>/typescript/lib/lib.dom.d.ts"
}
Expand All @@ -32,8 +32,8 @@
"value": "HTMLButtonElement",
"location": {
"range": {
"start": { "line": 13261, "character": 10 },
"end": { "line": 13261, "character": 27 }
"start": { "line": 17284, "character": 10 },
"end": { "line": 17284, "character": 27 }
},
"uri": "<node_modules>/typescript/lib/lib.dom.d.ts"
}
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1 change: 1 addition & 0 deletions packages/language-server/test/plugins/typescript/service.test.ts
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Expand Up @@ -632,6 +632,7 @@ describe('service', () => {
compilerOptions: {
composite: true,
strict: true,
module: 'NodeNext',
moduleResolution: 'NodeNext'
},
files: ['index.ts']
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8 changes: 5 additions & 3 deletions packages/language-server/tsconfig.json
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Expand Up @@ -2,8 +2,8 @@
"compilerOptions": {
"lib": ["es2021"],
"target": "es2021",
"moduleResolution": "node",
"module": "CommonJS",
"moduleResolution": "node16",
"module": "node16",

"outDir": "dist",
"strict": true,
Expand All @@ -12,6 +12,8 @@
"sourceMap": true,
"composite": true,
"skipLibCheck": true,
"forceConsistentCasingInFileNames": true
"rootDir": ".",
"forceConsistentCasingInFileNames": true,
"types": ["@types/mocha"]
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}
}
2 changes: 1 addition & 1 deletion packages/svelte-check/package.json
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Expand Up @@ -56,7 +56,7 @@
"svelte2tsx": "workspace:*",
"svelte": "^4.2.19",
"svelte-language-server": "workspace:*",
"typescript": "^5.9.2",
"typescript": "^6.0.2",
"vscode-languageserver": "8.0.2",
"vscode-languageserver-protocol": "3.17.2",
"vscode-languageserver-types": "3.17.2",
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2 changes: 1 addition & 1 deletion packages/svelte-vscode/package.json
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Expand Up @@ -760,7 +760,7 @@
"js-yaml": "^3.14.0",
"semver": "^7.7.2",
"tslib": "^2.4.0",
"typescript": "^5.9.2",
"typescript": "^6.0.2",
"vitest": "^3.2.4",
"textmate-grammar-test": "^0.6.0"
},
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2 changes: 1 addition & 1 deletion packages/svelte-vscode/test/sveltekit/utils.spec.ts
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Expand Up @@ -113,7 +113,7 @@ describe('checkProjectKind', () => {
it(name, async () => {
setupMocks(config);

const utils = await import('../../src/sveltekit/utils');
const utils = await import('../../src/sveltekit/utils.js');
const result = await utils.checkProjectKind('/test/path');

expect(result[ex]).toBe(toBe);
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4 changes: 2 additions & 2 deletions packages/svelte-vscode/tsconfig.json
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@@ -1,9 +1,9 @@
{
"compilerOptions": {
"lib": ["es2021"],
"module": "CommonJS",
"module": "node16",
"target": "es2021",
"moduleResolution": "node",
"moduleResolution": "node16",

"outDir": "dist",
"strict": true,
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4 changes: 2 additions & 2 deletions packages/svelte2tsx/package.json
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Expand Up @@ -40,11 +40,11 @@
"svelte": "~4.2.19",
"tiny-glob": "^0.2.6",
"tslib": "^2.4.0",
"typescript": "^5.9.2"
"typescript": "^6.0.2"
},
"peerDependencies": {
"svelte": "^3.55 || ^4.0.0-next.0 || ^4.0 || ^5.0.0-next.0",
"typescript": "^4.9.4 || ^5.0.0"
"typescript": "^4.9.4 || ^5.0.0 || ^6.0.0"
},
"scripts": {
"build": "rollup -c",
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1 change: 1 addition & 0 deletions packages/svelte2tsx/test/emitDts/samples/javascript/jsconfig.json
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@@ -1,5 +1,6 @@
{
"compilerOptions": {
"strict": false,
"checkJs": true
},
"include": ["./src/**/*.d.ts", "./src/**/*.js", "./src/**/*.ts", "./src/**/*.svelte"]
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7 changes: 4 additions & 3 deletions packages/svelte2tsx/test/tsconfig.json
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Expand Up @@ -2,9 +2,10 @@
"compilerOptions": {
"types": ["@types/node", "@types/mocha"],
"target": "es6",
"module": "commonjs",
"moduleResolution": "node",
"esModuleInterop": true
"module": "nodenext",
"moduleResolution": "nodenext",
"esModuleInterop": true,
"rootDir": "."
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},
"exclude": ["samples/**"],
"include": ["*.ts"]
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8 changes: 7 additions & 1 deletion packages/svelte2tsx/tsconfig.json
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@@ -1,5 +1,6 @@
{
"compilerOptions": {
"strict": false,
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@dummdidumm dummdidumm Apr 2, 2026

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one day we will mark this strict and fight all the errors that come from it 😆

"target": "es2018",
"lib": ["ES2018"],
"rootDir": "src",
Expand All @@ -12,14 +13,19 @@
//let rollup handle these
"module": "esnext",
"moduleResolution": "node",

// rollup typescript plugin currently override moduleResolution to node
"ignoreDeprecations": "6.0",
"resolveJsonModule": true,
"allowSyntheticDefaultImports": true,
"forceConsistentCasingInFileNames": true,

"noImplicitThis": true,
"noUnusedLocals": true,
"noUnusedParameters": true
"noUnusedParameters": true,
"types": ["node"]
},
"include": ["src/*"],
"paths": {
"@/*": ["src/*"]
},
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2 changes: 1 addition & 1 deletion packages/typescript-plugin/package.json
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Expand Up @@ -25,7 +25,7 @@
"devDependencies": {
"@types/node": "^18.0.0",
"svelte": "^4.2.19",
"typescript": "^5.9.2"
"typescript": "^6.0.2"
},
"dependencies": {
"@jridgewell/sourcemap-codec": "^1.5.0",
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4 changes: 2 additions & 2 deletions packages/typescript-plugin/tsconfig.json
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Expand Up @@ -2,8 +2,8 @@
"compilerOptions": {
"lib": ["es2021"],
"target": "es2021",
"moduleResolution": "node",
"module": "CommonJS",
"moduleResolution": "node16",
"module": "node16",

"outDir": "dist",
"esModuleInterop": true,
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