Better error message when requiring AVA from a REPL

[novemberborn]

This output isn't useful at all:

❯ node -p "require('ava')"
path.js:39
    throw new ERR_INVALID_ARG_TYPE('path', 'string', path);
    ^

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined
    at assertPath (path.js:39:11)
    at Object.relative (path.js:1173:5)
    at Object.<anonymous> (/private/var/folders/2_/qczp184x76b2nl034sq5hvxw0000gn/T/tmp.x2ORUONLHR/node_modules/ava/lib/worker/ensure-forked.js:8:18)
    at Module._compile (internal/modules/cjs/loader.js:689:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Module.require (internal/modules/cjs/loader.js:637:17)
    at require (internal/modules/cjs/helpers.js:20:18)

The problem is in this line:

ava/lib/worker/ensure-forked.js

Line 8 in fd73358

const fp = path.relative('.', process.argv[1]);

When using the REPL, process.argv[1] is empty. We should detect this and have a better error message.

[sanchitbansal10]

I would like to fix this..Thanks

[novemberborn]

Hi @sanchitbansal10, there's already a PR for this: #1871. Hopefully you'll find another issue you'd like to work on 👍