Summary

When using Prettier v2.7's --cache flag, it is possible that files may become cached in such a way that they will not be fixed. Specifically, calling Prettier with the --list-different and --cache flags in the same command will cause the state of the file to be cached, such that a subsequent run of prettier with --write and --cache will not format the file.

About this Reproduction

This reproduction contains the following files of interest:

.
├── index.js
└── package.json

index.js

this file contains a single 'hello world' console.log() statement. the statement does not have a semicolon at the end of it, which should be added according to Prettier's default settings.

package.json

this file contains the output of running npm init -y. it was then updated to add prettier v2.7.1 as a dev dependency (this can be reproduced with v2.7.0 as well)

Steps to Reproduce

After cloning this repository, open a terminal and run Prettier with both the list-different and cache flags:

npx prettier . --list-different --cache

Observe that index.js is listed in the output.

Next, run Prettier to format the code:

npx prettier . --write --cache

Observe that index.js is cached:

index.js 1ms (cached)
package-lock.json 1ms (cached)
package.json 0ms (cached)
README.md 1ms (cached)

The index.js file will not be formatted (note lack of semicolon):

$ cat index.js
// note the lack of semicolon in this file, which should be added
// by Prettier's default settings
console.log('hello world')

Considerations

It is possible that the best advice here is to not run prettier with the --list-different and --cache flags. Omitting --cache clears the cache, so a call like npx prettier . --list-different won't cause any issues in that respect.

Environment

npm: v8.3.1 Node: v16.14.0 OS: MacOS v12.3.1