toMatchInlineSnapshot produces invalid code when called inside a loop

[silverwind]

Describe the bug

Calling toMatchInlineSnapshot within a loop produces invalid code:

import {test, expect} from "vitest";

test("snap", () => {
  for (const str of ["foo", "bar"]) {
    expect(str).toMatchInlineSnapshot();
    // transforms to expect(str).toMatchInlineSnapshot(`"foo"``"bar"`);
  }
});

The transformed code produces a runtime error:

TypeError: "\"foo\"" is not a function

Typescript also does not like it:

src/basic.test.ts:5:39 - error TS2349: This expression is not callable.
  Type 'String' has no call signatures.

8     expect(str).toMatchInlineSnapshot(`"foo"``"bar"`);

Reproduction

https://stackblitz.com/edit/vitest-dev-vitest-r8dfgp?file=src%2Fbasic.test.ts

Validations

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[sheremet-va]

toMatchInlineSnapshot is not supported in a loop. We even throw an error when it's called in test.each.

[sheremet-va]

I guess we can try to find a way to throw an error here for a better DX, but I don't have ideas how. I will keep the issue open for now.

[hi-ogawa]

I remembered Jest throws a better error for this case. I haven't checked how they do, but made a quick repro for a reference https://stackblitz.com/edit/github-tj5mf5?file=basic.test.js

 FAIL  ./basic.test.js
  ● Test suite failed to run

    Jest: Multiple inline snapshots for the same call are not supported.

[silverwind]

Could it be supported, though? It should be possible to encode multiple values in one string, but likely it will need some creative escaping to support all possible values.

[sheremet-va]

Could it be supported, though? It should be possible to encode multiple values in one string, but likely it will need some creative escaping to support all possible values.

I don't think it could be supported or should be supported. It is much harder to support internally and it makes the result code look even less readable. Use toMatchSnapshot if you want to generate snapshots in a loop.