Cannot boot with external node_modules

[krukid]

I'm sure that at some point there was support for node_modules that were located outside of the Ember project root, however it's not clear to me if it's a living thing anymore. This feature is poorly documented, although I've been able to piece some info based on source code, closed issues and proof-of-concept projects, i.e.:

#3735
#3771
#7401
https://github.com/ember-cli/ember-cli/blob/master/lib/models/project.js#L352
https://github.com/bantic/test-app

There seem to have been 3 separate attempts at this:

1. Elusive nodeModulesPath config key that has been deprecated (possibly addon-specific).
2. Transient EMBER_NODE_PATH that seems to have some effect when combined with NODE_PATH, short of booting the app though.
3. Some kind of module lookup refactoring intended to match native NodeJS lookup that does not seem to be working.

I have tried:

1. setting nodeModulesPath, because it seemed like a logical thing to try;
2. using Yarn with --modules-folder config in .yarnrc that Ember failed to detect;
3. moving node_modules to one of the locations that native NodeJS lookup would find;
4. using export EMBER_NODE_PATH=$HOME/.node_modules && export NODE_PATH=$EMBER_NODE_PATH, that prints:

root@112bd0501087:/app# ember s
WARNING:
WARNING: The 'package.json' file for the project at /app
WARNING:   specifies some missing dependencies:
WARNING:     @ember/jquery
WARNING:     @ember/optional-features
WARNING:     broccoli-asset-rev
WARNING:     ember-ajax
WARNING:     ember-cli
WARNING:     ember-cli-app-version
WARNING:     ember-cli-babel
WARNING:     ember-cli-eslint
WARNING:     ember-cli-htmlbars
WARNING:     ember-cli-htmlbars-inline-precompile
...
Missing template processor

So, maybe it's not supported anymore? Or broken? Or is there something I can tweak to make this work?

---

Output from ember version --verbose && npm --version && yarn --version:

ember-cli: 3.5.0
http_parser: 2.8.0
node: 10.8.0
v8: 6.7.288.49-node.19
uv: 1.22.0
zlib: 1.2.11
ares: 1.14.0
modules: 64
nghttp2: 1.32.0
napi: 3
openssl: 1.1.0h
icu: 62.1
unicode: 11.0
cldr: 33.1
tz: 2018e
os: linux x64
6.2.0
1.9.2

[krukid]

I've been able to work around this with Yarn workspaces. Some suggest using NPM with Lerna, but I haven't tried that yet.

[locks]

Thanks for filling such a detailed issue! I am closing it as a lot has happened, what with Yarn workspaces, npm workspaces, etc, etc, that I think this would need to be re-thought.