relx can't find app

[rlipscombe]

See ninenines/cowboy#1593.

The working directory has to match the application name. A dash followed by a version may be present. Without this, you get a hard-to-understand error:

init terminating in do_boot ({{error,{rlx_resolve,{app_not_found,middleware,undefined}}},
[{rlx_resolve,find_app_in_code_path,2,[{_},{_}]},{rlx_resolve,subset,6,[{_},{_}]},{rlx_resolve,solve_release,2, 

(wrapped for "readability"; the app is called middleware)

The important bit is {error,{rlx_resolve,{app_not_found,APPLICATION_NAME,undefined}}}.

This is particularly a problem if you're building inside a container (because it's common to use WORKDIR /build, and that's not gonna match).

[FrancescoRestelli]

this really needs some attention, i went and patched my own version of rlx_resolve.erl to solve this in the past, however that broke now with otp26 :)

please add a nice print

[pavel-baturko-sb]

this is an annoying issue, especially in CI environments

[essen]

Best I can do is a nicer error message. This is an expectation of OTP that the folder name matches the application name (with an optional dash followed by anything you want). A PR implementing the nicer error message is welcome.