feat: support TypeScript 6#675
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teemingc
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Apr 1, 2026
closes #15372 This PR extends the SvelteKit peerDep range to include TS 6.0. It also upgrades our apps/packages using TS purely as a devDependency to use 6.0 (this excludes `kit` because we use TS to generate public types and that can be a breaking change. `package` is also excluded because it can't support TS6 until svelte2tsx does). ### TODOs - [x] update `svelte-check` sveltejs/language-tools#2988 Required for `@sveltejs/package` if we want to support TS6 in the future: - [ ] update `svelte2tsx` sveltejs/language-tools#2985 - [ ] update `svelte-preprocess` sveltejs/svelte-preprocess#675 Required for SvelteKit 3 when we switch over to TS6 completely - [x] update `@sveltejs/eslint-config` sveltejs/eslint-config#67 - [ ] update `dts-buddy` sveltejs/dts-buddy#123 --- ### Please don't delete this checklist! Before submitting the PR, please make sure you do the following: - [ ] It's really useful if your PR references an issue where it is discussed ahead of time. In many cases, features are absent for a reason. For large changes, please create an RFC: https://github.com/sveltejs/rfcs - [ ] This message body should clearly illustrate what problems it solves. - [ ] Ideally, include a test that fails without this PR but passes with it. ### Tests - [ ] Run the tests with `pnpm test` and lint the project with `pnpm lint` and `pnpm check` ### Changesets - [ ] If your PR makes a change that should be noted in one or more packages' changelogs, generate a changeset by running `pnpm changeset` and following the prompts. Changesets that add features should be `minor` and those that fix bugs should be `patch`. Please prefix changeset messages with `feat:`, `fix:`, or `chore:`. ### Edits - [ ] Please ensure that 'Allow edits from maintainers' is checked. PRs without this option may be closed.
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Thank you for this patch, I look forward to it landing and releasing to npm so it resolves the peer dependency resolution issue blocking our project's upgrade to TS 6. ❤️ |
teemingc
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May 19, 2026
teemingc
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May 21, 2026
| aliases, | ||
| markupTagName = 'template', | ||
| sourceMap = process?.env?.NODE_ENV === 'development' ?? false, | ||
| sourceMap = process?.env?.NODE_ENV === 'development' || false, |
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Fixes this TypeScript error
Right operand of ?? is unreachable because the left operand is never nullish.
teemingc
commented
May 21, 2026
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| expect(code).toBe(`<script lang="ts" context="module"></script>`); | ||
| expect(code).toBe( | ||
| `<script lang="ts" context="module">export {};\n</script>`, |
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Empty modules created with NodeNext always have export {} while ESNext simply has "use strict"
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This PR adds TS6 support by ensuring source files adhere to TS6 rules and updating one of the tests to expect the appropriate contents for a
module: NodeNextoutputBefore submitting the PR, please make sure you do the following
pnpm lint!)Tests
npm testorpnpm test