fix(types): allow global.Netlify declaration merging
#494
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This fixes a TypeScript error that occurs when both `@netlify/[email protected]` and `@netlify/functions` are installed in a project (with `skipLibCheck: false`). It would fail with: ``` Error: TS2451: Cannot redeclare block-scoped variable 'Netlify' ``` See for example #489. You would think it wouldn't be valid to use both those packages at once, but TypeScript global module augmentation is truly _global_ - it doesn't care where you import a package that performs global module augmentation; your whole TS project is compiled/typechecked as one program, unless you explicitly configure things completely separately for your `./netlify/functions` vs. `./netlify/edge-functions` vs. `src/`... which pretty much no one does. TypeScript allows multiple `var` declarations in a scope to merge, but `const` declarations are cannot be redeclared. When both packages declare `global.Netlify`, they must both use `var` for the declarations to merge successfully. We were actually already doing this correctly, but unfortunately there was a comment that was lying about _why_ (and there was no type test covering this). This led me to change it to `const` in #434. I went down a rabbit hole trying to add a regression type test for this but I had to cut my losses after running into some issues.
JakeChampion
approved these changes
Oct 22, 2025
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This fixes a TypeScript error that occurs when both
@netlify/[email protected]and@netlify/functionsare installed in a project (withskipLibCheck: false).It would fail with:
See for example #489.
You might think it wouldn't be valid to use both those packages at once, but TypeScript global module augmentation is truly global - it doesn't care where you import a package that performs global module augmentation; your whole TS project is compiled/typechecked as one program, unless you explicitly configure things completely separately for your
./netlify/functionsvs../netlify/edge-functionsvs.src/... which pretty much no one does.TypeScript allows multiple
vardeclarations in a scope to merge, butconstdeclarations are cannot be redeclared. When both packages declareglobal.Netlify, they must both usevarfor the declarations to merge successfully.We were actually already doing this correctly, but unfortunately there was a comment (copypasta from here, where it was accurate) that was lying about why (and there was no type test covering this). This led me to change it to
constin #434.I went down a rabbit hole trying to add a regression type test for this but I had to cut my losses after running into some issues. 😢