v6: `undefined` Added to Record Type

[joealden]

Bug Report

When upgrading from 5.1.0 to 6.0.0, merging two records that both have types of Record<string, string> results in a type of { [x: string]: string | undefined; }, when I'd expect it to be { [x: string]: string; }.

EDIT: I understand that Record<string, string> isn't actually accurate for a concrete object that isn't proxied (as any properties not defined won't actually exist, so will be undefined), but if foo and bar have that type, I'd expect it to be respected (like it is in 5.1.0).

Expected behavior

const foo: Record<string, string> = { fooProp: "" };
const bar: Record<string, string> = { barProp: "" };
const result = deepmerge(foo, bar);
//         ^? result: { [x: string]: string; }

Actual behavior

const foo: Record<string, string> = { fooProp: "" };
const bar: Record<string, string> = { barProp: "" };
const result = deepmerge(foo, bar);
//         ^? result: { [x: string]: string | undefined; }

[github-actions]

🎉 This issue has been resolved in version 6.0.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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