How to proxy with Gatsby and custom Webpack config (netlify-lambda) - webpack-dev-server

Question

I'm using Gatsby with netlify-lambda which creates a server for functions on the 9000 ports:
http://localhost:9000/myFunctionName
In production the address of the functions is:
/.netlify/functions/myFunctionName
So I would like to have a dev mode proxy that serves http://localhost:9000/ when I call /.netlify/functions.
My custom Webpack config in gatsby-node.js:
exports.modifyWebpackConfig = ({ config, stage }) => {
if (stage === 'develop') {
config.merge({
devServer: {
proxy: {
'/.netlify/functions': {
target: 'http://localhost:9000',
pathRewrite: {
'^/\\.netlify/functions': ''
}
}
}
}
})
}
}
Does not work.
I tried this too https://www.gatsbyjs.org/docs/api-proxy/#api-proxy but I need to rewrite the url and not just prefix.
What's the best way to use netlify-lambda with Gatsby ?
Thanks

Answer 1

Update: Gatsby now does support Express middleware, in this merged PR. This will not support the Webpack Dev Server proxy configuration, but will allow using ordinary Express proxy middleware.
To use with netlify-lambda just add this to your gatsby-config.js :
const proxy = require("http-proxy-middleware")
module.exports = {
developMiddleware: app => {
app.use(
"/.netlify/functions/",
proxy({
target: "http://localhost:9000",
pathRewrite: {
"/.netlify/functions/": "",
}
})
)
}
}
https://www.gatsbyjs.org/docs/api-proxy/#advanced-proxying
Unfortunately, the Gatsby development proxy configuration is not at all extensible. Since Gatsby does not use the webpack dev server, its proxy options are not available. See https://github.com/gatsbyjs/gatsby/issues/2869#issuecomment-378935446
I achieve this use case by putting an nginx proxy in front of both my Gatsby development server and the netlify-lambda server. This is a very simplified version of the proxy server config (trailing slash is important):
server {
listen 8001;
location /.netlify/functions {
proxy_pass http://0.0.0.0:9000/;
}
location / {
proxy_pass http://0.0.0.0:8000;
}
}
I'm using an nginx proxy anyhow, so that's not an undesirable amount of extra dev setup, but it would certainly be better if Gatsby supported this common case.