Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

improve typing for getFieldValueFromKeyString #146

Draft
wants to merge 1 commit into
base: main
Choose a base branch
from
Draft

improve typing for getFieldValueFromKeyString #146

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
44 changes: 44 additions & 0 deletions src/js/types.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -97,3 +97,47 @@ export function isValidatorStepArrayArray(dependent?: Dependent): dependent is A
export function isValidatorStep(dependent?: boolean | ValidatorStep): dependent is ValidatorStep {
return !!dependent && Array.isArray(dependent) && !Array.isArray(dependent[0]);
}


type ResultType<S extends string|number, V extends Value> =
S extends number
? V extends Array<infer A>
? A
: undefined
: S extends `${infer First}.${infer Rest}`
? V extends Record<any, any>
? ResultType<Rest, V[First]>
: never
: S extends `${infer Last}`
? V extends Record<any, any>
? V[Last]
: undefined
: never;

const getFieldValueFromKeyString = <S extends string|number, T extends Value>(
keyString: S, values: T,
): ResultType<S, T> => {
const fieldNames = String(keyString).split('.');
let dependentValue = values;
for (const fieldName of fieldNames) {
if ((dependentValue as ObjectValue)[fieldName] === undefined) {
throw new Error('Could not find value for ' + keyString);
}
dependentValue = (dependentValue as any)[fieldName];
}
return dependentValue as ResultType<S, T>;
};


// todo: the calls that result in an "unknown" type should ideally result in "undefined" instead
// todo: need to test if the calls resulting in undefined actually return undefined; if they error, type them never
const t = getFieldValueFromKeyString('test.1.str', {test: [{str: 'yay!'}]}); // string
const t2 = getFieldValueFromKeyString(0, ['3', '2']); // string
const t3 = getFieldValueFromKeyString('0', ['3', '2']); // string
const t4 = getFieldValueFromKeyString('test.1', {test: [{str: 'yay!'}]}); // {str: string}

const b = getFieldValueFromKeyString('test.1.str.5', {test: [{str: 'yay!'}]}); // undefined
const b2 = getFieldValueFromKeyString('test.1.strrrrrr', {test: [{str: 'yay!'}]}); // unknown :(
const b3 = getFieldValueFromKeyString('test.1.str.sss', {test: [{str: 'yay!'}]}); // undefined
const b5 = getFieldValueFromKeyString('02', ['3', '2']); // unknown :(
const b6 = getFieldValueFromKeyString(1, {test: [{str: 'yay!'}]}); // undefined
Loading