jest: Prettier is used by `toMatchInlineSnapshot`, but it is not a dependency of `jest`

🐛 Bug Report

Prettier is used by jest for toMatchInlineSnapshot, but since it’s not a dependency of jest, toMatchInlineSnapshot only works if some other package depends on prettier (or it’s in the user’s package.json).

To Reproduce

Steps to reproduce the behavior:

Make a new directory and run yarn init --yes inside it
Run yarn add jest
Create a test using the toMatchInlineSnapshot matcher, eg:
```
expect(2 + 2).toMatchInlineSnapshot()
```
Notice that the test fails with an error indicating that prettier cannot be found.

Expected behavior

Test passes with no issues

`npx envinfo --preset jest`

  System:
    OS: macOS 10.14.4
    CPU: x64 Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
  Binaries:
    Node: 12.1.0 - /usr/local/bin/node
    Yarn: 1.13.0 - /usr/local/bin/yarn
    npm: 6.9.0 - /usr/local/bin/npm
  npmPackages:
    jest: 24.8.0 => 24.8.0

About this issue

Original URL
State: closed
Created 5 years ago
Reactions: 34
Comments: 16 (9 by maintainers)

Commits related to this issue

Install prettier, but only to support 'toMatchInlineSnapshot' in jest tests https://github.com/facebook/jest/issues/8467#issuecomment-617459378 — committed to johnnyoshika/prisma-nexus-postgres by johnnyoshika 3 years ago
create snapshot test case & add prettier for using 'toMatchInlineSnapshot' ref: https://github.com/facebook/jest/issues/8467 — committed to linnefromice/graphql_practice by linnefromice 3 years ago

Most upvoted comments

looks like it is supposed to throw a descriptive error message:

https://github.com/facebook/jest/blob/fa4cbbf87cb3c97fe44f1fee30663715a9dbba71/packages/jest-snapshot/src/inline_snapshots.ts#L33-L35

The error message that I get with jest-cli@25.4.0 is:

Cannot find module 'prettier' from 'setup_jest_globals.js'

+12

UziTech on Apr 21, 2020

Oh, nice!

A descriptive error message saying “you need to install prettier” might be good enough, too

yeah, we should definitely to that as a first step regardless. #7744

SimenB on May 15, 2019

Hmm. Not sure; thanks for the context.

Maybe it should be listed as a peerdep? A descriptive error message saying “you need to install prettier” might be good enough, too. It’s unexpected to get a “could not find prettier” error the first time you use .toMatchInlineSnapshot.

Not sure if this makes sense for jest, but prettier could be replaced with babel + recast here, and it could use prettier for printing (instead of recast) as an optimization, when it’s available.

suchipi on May 14, 2019

I just ran into this as well.

kevinbarabash on Jul 6, 2019

Maybe the error message should at least state that prettier must be installed to use toMatchInlineSnapshot. I just spent way too long wondering what was throwing the error. I definitely did not think jest was using a package without requiring it as a dependency. That seems like an obvious code smell.

UziTech on Apr 21, 2020

Would you expect jest to bundle some version and defer to a local one? Related #7792

SimenB on May 14, 2019