How can you get Grunt livereload to work inside Do

Question

I'm trying to use Docker as a dev environment in Windows.

The app I'm developing uses Node, NPM and Bower for setting up the dev tools, and Grunt for its task running, and includes a live reload so the app updates when the code changes. Pretty standard. It works fine outside of Docker but I keep running into the Grunt error Fatal error: Unable to find local grunt. no matter how I try to do it inside Docker.

My latest effort involves installing all the npm and bower dependencies to an app directory in the image at build time, as well as copying the app's Gruntfile.js to that directory.

Then in Docker-Compose I create a Volume that is linked to the host app, and ask Grunt to watch that volume using Grunt's --base option. It still won't work. I still get the fatal error.

Here are the Docker files in question:

Dockerfile:

# Pull base image.
FROM node:5.1

# Setup environment
ENV NODE_ENV development

# Setup build folder
RUN mkdir /app
WORKDIR /app

# Build apps
#globals
RUN npm install -g bower
RUN echo '{ "allow_root": true }' > /root/.bowerrc
RUN npm install -g grunt
RUN npm install -g grunt-cli
RUN apt-get update
RUN apt-get install ruby-compass -y
#locals
ADD package.json /app/
ADD Gruntfile.js /app/
RUN npm install
ADD bower.json /app/
RUN bower install

docker-compose.yml:

angular:
 build: .
 command: sh /host_app/startup.sh
 volumes:
   - .:/host_app
 net: "host"

startup.sh:

#!/bin/bash
grunt --base /host_app serve 

The only way I can actually get the app to run at all in Docker is to copy all the files over to the image at build time, create the dev dependencies there and then, and run Grunt against the copied files. But then I have to run a new build every time I change anything in my app.

There must be a way? My Django app is able to do a live reload in Docker no problems, as per Docker's own Django quick startup instructions. So I know live reload can work with Docker.

PS: I have tried leaving the Gruntfile on the Volume and using Grunt's --gruntfile option but it still crashes. I have also tried creating the dependencies at Docker-Compose time, in the shared Volume, but I run into npm errors to do with unpacking tars. I get the impression that the VM can't cope with the amount of data running over the shared file system and chokes, or maybe that the Windows file system can't store the Linux files properly. Or something.