Unclear error for missing "source"

[JasonEtco]

Current Behavior

Tried dropping TSDX into an existing library, and got this:

> [email protected] build /Users/jasonetco/dev/actions-toolkit
> tsdx build

TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received type undefined

    at assertPath (path.js:39:11)
    at Object.resolve (path.js:1088:7)
    at Object.exports.resolveApp (/Users/jasonetco/dev/actions-toolkit/node_modules/tsdx/dist/utils.js:19:27)
    at Object.createRollupConfig (/Users/jasonetco/dev/actions-toolkit/node_modules/tsdx/dist/createRollupConfig.js:29:24)
    at createBuildConfigs (/Users/jasonetco/dev/actions-toolkit/node_modules/tsdx/dist/index.js:30:30)
    at prog.command.describe.action (/Users/jasonetco/dev/actions-toolkit/node_modules/tsdx/dist/index.js:130:37)
    at Sade.parse (/Users/jasonetco/dev/actions-toolkit/node_modules/sade/lib/index.js:153:56)
    at Object.<anonymous> (/Users/jasonetco/dev/actions-toolkit/node_modules/tsdx/dist/index.js:168:6)
    at Module._compile (internal/modules/cjs/loader.js:688:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:699:10)

After some 🤔, turns out it was expecting a "source" property in my package.json.

Expected behavior

A handy-dandy error like:

Hey you need a `source` property in your package.json, pointing to the entrypoint of your library

Your environment

Software	Version(s)
TSDX	v0.0.25

[jaredpalmer]

Yep.

[jaredpalmer]

Source is now the fallback. The default is src/index.ts or src/index.tsx. You can override this by passing --entry src/foo.tsx flag in build or watch