safeRequire returning undefined even when module is installed

[ritch]

We're running into an issue where the following setup is causing
https://github.com/strongloop/loopback/blob/master/lib/express-middleware.js#L8 to return undefined.

arc depends on loopback
arc depends on workspace
workspace depends on loopback
workspace depends on cookie-parser

Since the versions are compatible (I assume) npm installs only one loopback package in arc's node_modules directory (and nothing in workspace). This breaks the assumptions safeRequire() makes - which is that the loopback will be a dependency of the module that has the independent middleware installed (eg. serve-favicon, which is installed in workspace).

I'm not exactly sure how we can fix this with npm's behavior. Npm chooses to install only a single loopback module. Currently we just install the modules in arc. This is a bit unsettling because they are not arc's dependencies (they are workspace's).

[bajtos]

I think the correct fix is to stop using loopback.{name} shortcuts and load the middleware directly via require. See strongloop/loopback-workspace#166 for an example of such change.

It would be even better to 1) upgrade loopback-workspace to use the new 2.x project layout 2) convert it to a proper loopback component, so that strong-arc can import workspace models into the main strong-arc app.

[bajtos]

BTW I have run into the same problem when I was npm link-ing loopback to a different project. Node module lookup uses the real path (e.g. ~/src/loopback), not the symlink path (e.g. ~/src/loopback-boot/node_modules/loopback) and thus it look into ~/src/loopback-boot/node_modules when resolving require called from loopback.

We should use as much middleware as we can directly, and use loopback shortcuts only where necessary: loopback.static and loopback.favicon.

[bajtos]

I believe this issue is a duplicate of strongloop/loopback-boot#73

[bajtos]

This should be fixed as of loopback-boot@2.7.0. Please upgrade your projects to use this new version and reopen this issue if the problem still persists.