When a project uses other tool for build and is not rebar3 discoverable prior to compilation (E.g.: rabbitmq_common), we could use pre hooks to compile it and also to generate the .app.src, .app files.

The following rebar.config still fails though:

{deps, [{rabbit_common, {git, "https://github.com/rabbitmq/rabbitmq-common.git", {ref, "9719670db30"}}}]}.

{overrides, [{override, rabbit_common, [{pre_hooks, [{compile, "make"}]}]}]}.

with error:

===> Dependency failure: source for rabbit_common does not contain a recognizable project and can not be built

The above error is from 3.7.5.

3.6.2 fails as well:

===> Dependency failure: Application rabbit_common not found at the top level of directory ...

Fetching the dependency calls rebar_app_discover:find_app/3 here:
https://github.com/erlang/rebar3/blob/3.7.5/src/rebar_fetch.erl#L33
which expects the .app.src or .app file to be present which in this case are generated by make.

If we could tell rebar3 not fail so quickly here:
https://github.com/erlang/rebar3/blob/3.7.5/src/rebar_fetch.erl#L36
maybe by replacing the throw https://github.com/erlang/rebar3/blob/3.7.5/src/rebar_fetch.erl#L37
with rebar_app_info:is_available(AppInfo1, true) we might have a solution.

             case rebar_app_discover:find_app(AppInfo1, AppDir, all) of
                 {true, AppInfo2} ->
                     rebar_app_info:is_available(AppInfo2, true);
                 false ->
-                    throw(?PRV_ERROR({dep_app_not_found, rebar_app_info:name(AppInfo1)}))
+                    rebar_app_info:is_available(AppInfo1, true)
             end;

This solves the problem but I am unsure about the consequences. Should be a rebar_app_discover:find_app/3 call between prehook of compile and compile to double check for the "app.src" later?