CLI with config option throws "cannot read property 'sync' of undefined" since 1.14.0

[alexandernanberg]

Environments:

• Prettier Version: 1.14.2
• Running Prettier via: CLI
• Runtime: Node 8.11.3
• Operating System: MacOS 10.13.6

Steps to reproduce:
Run the following (this expects that you have a .prettierrc.examples file and a examples dir with code in it)

prettier --config .prettierrc.examples --write \"examples/**/*.js\"

Expected behavior:
Prettier should format my files inside the examples dir without any errors

Actual behavior:
Throws this error

Invalid configuration file: Cannot read property 'sync' of undefined

This worked prior to 1.14.1. Is there some workaround to this?

[ikatyang]

We updated cosmiconfig to v5 in #4899 (1.14.1), which should probably be the cause. But a config file with .examples extension is not something we supported, we only support config files with no extension (written in JSON/YAML) or one of the supported extensions.

I think the issue here is that the error message needs to be improved, we should open an issue there.

Edit: tracked in cosmiconfig/cosmiconfig#153

[alexandernanberg]

I see, in my case simply renaming the file to .prettierrc and moving it the examples dir solved the problem.

Thanks!