interface RegExpMatchArray in lib.es2018.regexp.d.ts

[WesleyMConner]

lib Update Request

Configuration Check

My compilation target is es2022 and my lib is the default.

Missing / Incorrect Definition

Currently in ts > lib > lib.es2018.regexp.d.ts:

interface RegExpMatchArray {
  groups?: {
    [key: string]: string
  }
}

Per the Sample Code below, it looks like the interface should be:

interface RegExpMatchArray {
  groups?: {
    [key: string]: string | undefined
                          ^^^^^^^^^^^
  }
}

Sample Code

Sample code

const s = 'The quick brown fox'
const m = /(?<a>The).*(?<b>quick).*(?<c>red)?.*(?<d>fox)/
const x = s.match(m)           // x: RegExpMatchArray | null
if (x) {
  const y = x.groups           // const y: { [key: string]: string; } | undefined
  if (y) {
    const a = y['a']           // string | undefined
    const b = y['b']           // string | undefined
    const c = y['c']           // string | undefined
    const d = y['d']           // string | undefined  
    console.log(y)
    //  => [Object: null prototype] {
    //       a: 'The',
    //       b: 'quick',
    //       c: undefined,
    //       d: 'fox'
    //     }
  }
}  

Documentation Link

https://github.com/microsoft/TypeScript/blob/main/lib/lib.es2018.regexp.d.ts

[MartinJohns]

You should enable noUncheckedIndexedAccess. It's the intended solution.

[WesleyMConner]

I already have "noUncheckedIndexedAccess": true," in tsconfig.json.

Let's say I want to write a function that consumes named CGs produced by string.match(RegExp)

Crude Placeholder Function

const operatesOnGroups = (x: {[key: string]: string}) => console.log(x)

There is no issue passing the data produced from a match into this placeholder function.

const s = 'The quick brown fox'
const m = /(?<a>The).*(?<b>quick).*(?<c>red)?.*(?<d>fox)/
const x = s.match(m)           // x: RegExpMatchArray | null
if (x) {
  const y = x.groups           // const y: { [key: string]: string; } | undefined
  if (y) {
    operatesOnGroups(y)
      => [Object: null prototype] {
           a: 'The',
           b: 'quick',
           c: undefined,
           d: 'fox'
         }
  }
} 

There is a problem if I want to simulate match output data for testing my function.

const testData = {
  a: 'The',
  b: 'quick',
  c: undefined,  // Simulating the undefined present in the match result.
  d: 'fox'
}
operatesOnGroups(testData)
  => error TS2345: Argument of type '{ a: string; b: string; c: undefined; d: string; }'
     is not assignable to parameter of type '{ [key: string]: string; }'.
     Property 'c' is incompatible with index signature.
       Type 'undefined' is not assignable to type 'string'.

For test data (with an embedded undefined) to work, I have to alter the signature of my placeholder function away from the signature present in ts > lib > lib.es2018.regexp.d.ts.

FROM:
const operatesOnGroups = (x: {[key: string]: string}) => console.log(x)
TO:
const operatesOnGroups = (x: {[key: string]: string | undefined}) => console.log(x)

[RyanCavanaugh]

This is the intended behavior of index signatures across the board.

[WesleyMConner]

Thanks

…

On Mon, Oct 24, 2022 at 7:13 PM Ryan Cavanaugh ***@***.***> wrote: This is the intended behavior of index signatures across the board. — Reply to this email directly, view it on GitHub <#51292 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEDVV4FTC24SREARHW5NXDDWE4JYHANCNFSM6AAAAAARNKOFDQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[typescript-bot]

This issue has been marked as 'Question' and has seen no recent activity. It has been automatically closed for house-keeping purposes. If you're still waiting on a response, questions are usually better suited to stackoverflow or the TypeScript Discord community.