Enable noUncheckedSideEffectImports by default in TypeScript 6.0 #62442
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This PR enables the
noUncheckedSideEffectImports
compiler flag by default for TypeScript 6.0, as requested in the original issue.Changes Made
Updated default value: Changed
defaultValueDescription
fromfalse
totrue
insrc/compiler/commandLineParser.ts
for thenoUncheckedSideEffectImports
flag.Fixed affected tests: Updated two fourslash tests that import non-existent modules by adding
// @noUncheckedSideEffectImports: false
directive to maintain their original behavior:tests/cases/fourslash/findAllRefsUnresolvedSymbols2.ts
tests/cases/fourslash/findAllRefsUnresolvedSymbols3.ts
Updated help baseline: The compiler help output now correctly shows
default: true
for thenoUncheckedSideEffectImports
flag.Impact
With this change, TypeScript will now check side-effect imports by default, helping developers catch potentially problematic imports of non-existent modules at compile time. This aligns with the goal of improving existing TypeScript configurations and reducing the need for manual flag configuration in new projects.
The change is backward compatible - existing projects can explicitly set
noUncheckedSideEffectImports: false
in theirtsconfig.json
if they need to maintain the previous behavior.Testing
This change has been successfully adopted by Vite starter templates and is ready for wider adoption as the new default behavior.
Additional instructions:
Fixes #62421
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