Wildcard and select() not working on property matching

[moifort]

Describe the bug
Wildcard __ and select() not working on property matching. As a workaround I use __.number

Code Sandbox with a minimal reproduction case
Result on console

https://codesandbox.io/s/nervous-turing-8cffw?file=/src/index.ts:0-937

Versions

• TypeScript version: 4.2.3
• ts-pattern version: 3.2.1
• environment: node 14

Sample code

import { match, select, __ } from "ts-pattern";

type Id = { teamId: number } | { storeId: number };

const selectedId: Id = { teamId: 1 };

// Bug with wildcard
const bugWildcard = match<Id>(selectedId)
  .with({ storeId: __ }, () => "storeId")
  .with({ teamId: __ }, () => "teamId")
  .exhaustive(); // Return storeId instead of teamId

console.log(
  "WILDCARD BUG",
  "match result:",
  bugWildcard,
  "value to match:",
  selectedId
);

// Bug with select
const value = match<Id>(selectedId)
  .with({ storeId: select() }, (storeId) => storeId)
  .with({ teamId: select() }, (teamId) => teamId)
  .exhaustive(); // Return nothing

console.log(
  "SELECT BUG",
  "match result:",
  value,
  "value to match:",
  selectedId
);

// Working with __.number
const number = match<Id>(selectedId)
  .with({ storeId: __.number }, () => "storeId")
  .with({ teamId: __.number }, () => "teamId")
  .exhaustive();

console.log("WORKING", "match result:", number, "value to match:", selectedId);

[gvergnaud]

I think what's happening is that since __ and select() always match, if you try to match on a property that doesn't exist on an object, it's actually undefined which matches the pattern.

It would probably make more sense if { abc: __ } was matching only if the abc key exists on the input, though. Is this what you were expecting?

I'll have a look at the TC39 pattern matching proposal to check how they plan to handle this case

[moifort]

@gvergnaud thanks for your quick answer!

[gvergnaud]

Fixed in v3.2.2!