npm ERR! missing script: start error with Docker

Question

When running docker-compose to launch my app, I'm getting a npm ERR! missing script: start despite having a start script specified.

package.json is

{
  "name": "myapp",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "body-parser": "~1.17.1",
    "cookie-parser": "~1.4.3",
    "debug": "~2.6.3",
    "ejs": "~2.5.6",
    "express": "~4.15.2",
    "mongoose": "^4.11.1",
    "morgan": "~1.8.1",
    "serve-favicon": "~2.4.2"
  }
}

and docker-compose.yml is

version: "2"
services:
  web:
    build: .
    volumes:
      - ./:/app
    ports:
      - "3500:3500"

2 things are not making sense to me:

1. Launching the app with its Dockerfile works: if the missing start script really was the problem, shouldn't this fail as well?
2. package.json does have a start script as you can see above

Not sure if needed but the Dockerfile is

FROM node:argon

RUN mkdir /app

WORKDIR /app

COPY package.json /app

RUN npm install

COPY . /app

EXPOSE 3500

ENV PORT 3500
CMD ["npm", "start"]

EDIT: I'm using docker run -p 3500:3500 app and docker-compose up

I'm new to this so may be missing something but am a bit stuck now.

Solution

You could try removing the volumes section - ./:/app
It looks like the /app is created within the container, but then subsequently you mount a host directory to /app, thus hiding the original /app in the container.