Strongly typed sprintf #15
Description
I just stumbled upon https://hacklewayne.com/a-truly-strongly-typed-printf-in-typescript and was wondering whether a solution like this could be considered for @tannin/sprintf.
Right now with the existing JSDoc every arg needs to be a string, when in fact the values will be cast to ints and floats anyway depending on the format. A strongly typed implementation could make this more robust.
This would also help catch issues where the number of arguments doesn't match the number of placeholders.
From that article:
type Specifiers = {
's': string,
'd': number,
'b': boolean,
'D': Date
};
type Spec = keyof Specifiers;
type Values<T extends string> =
T extends `${infer _}%${infer K}${infer Rest}`
? K extends Spec
? [ Specifiers[K], ...Values<Rest> ]
: Values<`${K}${Rest}`>
: [];
declare function printf<T extends string>(format: T, ...values: Values<T>): string;
const r = printf('this is a %s and it is %d %wyears old, right?%b %D %i %f', 'Hackle', 20, true, new Date()); // ok
printf('Hello %s', 'John'); // ok
printf('Hello %s', 'John', 'Doe'); // not ok, too many arguments
printf('Hello %s', false); // not ok, wrong typeNote: this doesn't support named arguments yet.