Follow main file in package.json

[StarpTech]

It is good practice to follow at first the package.json main file instead to load the default file.
This can avoid relative path issues.

e.g
build: ./herkules node-conpose should looking for the main file in the package section. If no package.json exists fallback to default behaviour 'index.js'

[platdesign]

Good idea, but not the most "docker-compose"-approach.

After the next patch-release node-compose determines the start command based on the following steps:

1. command attribute in image config (node-compose.yml). Thats the most "docker-compose"-way.
2. start-scriptattribute in package.json. The most "nodejs/npm"-way. Also best practice in most node-docker-base-images.
3. otherwise it will use node . The most opinionated way.

There might an additional way - maybe step 2.5 - to look for a start script in the bin directory of the image. Expressjs recommended a bin directory with a start-script. But i think three options are more than enough. ;)

[StarpTech]

This project has nothing in common with docker. Your features should reach the nodejs developer, that just said. Don't follow too much the "docker-compose" way. But your three approaches are good.

If you want to follow the "docker-compose" way I prefer to support only the first approach (configuration over convention).

[platdesign]

This project has nothing in common with docker.

Who claims sth else? It only should be configurable the same way as docker-compose.

Your features should reach the nodejs developer, that just said.

I'll hope they do! But the main-attribute from package.json is used to resolve the main-file during requiring. If you have a package which should be executable and loadable (microservice and its loadable client) the main-attribute will target at the client.

An additional idea is to check if the image has a dockerfile in CWD, parse it and read the CMD. This could be step 1.5.

Step 2 is for raw nodejs-devs only ;) The last one is only a "pre-fallback" before erroring.