Example Scenarios

Scenario 1: Single-App Project

Structure:

my_app/
├── rebar.config
└── src/
    ├── my_app.app.src
    └── my_app.erl

Discovery:

1. Scan root directory
2. Find src/my_app.app.src
3. Parse app resource
4. App dir = root directory
5. define_root_app returns <<"my_app">>
6. Single-app project detected

Result: One application in project_apps

Scenario 2: Umbrella Project

Structure:

my_project/
├── rebar.config
└── apps/
    ├── web/
    │   └── src/web.app.src
    └── db/
        └── src/db.app.src

Discovery:

1. Scan apps/ directory (from lib_dirs)
2. Find apps/web/src/web.app.src
3. Find apps/db/src/db.app.src
4. Parse both app resources
5. define_root_app returns root (no app at root)
6. Umbrella project detected

Result: Two applications in project_apps

Scenario 3: Custom Source Directories

rebar.config:

{src_dirs, ["src", "lib", "core"]}.

Structure:

my_app/
├── src/my_app.app.src
├── lib/helper.erl
└── core/engine.erl

Discovery:

1. Search src/, lib/, core/ for app resources
2. Find src/my_app.app.src
3. Associate all three directories with this app

Result: App discovered with multiple source directories

Scenario 4: Mix.exs Compatibility

Structure:

my_elixir_app/
├── mix.exs
└── lib/
    └── my_elixir_app.ex

Discovery:

1. Find mix.exs
2. Parse Elixir project configuration
3. Extract application metadata
4. Create app info compatible with rebar3

Result: Elixir app discoverable by rebar3

Scenario 5: Application-Specific Dependencies

apps/web/rebar.config:

{deps, [cowboy]}.

apps/db/rebar.config:

{deps, [epgsql]}.

Discovery:

1. Discover both apps
2. Read each app's rebar.config
3. Merge deps: web gets cowboy, db gets epgsql
4. Top-level deps also added to both

Result: Each app has appropriate dependencies