Application.compile_env-exclamation-mark

You're seeing just the macro compile_env-exclamation-mark, go back to Application module for more information.

compile_env!(app, key_or_path)

(macro) (since 1.10.0)

compile_env!(app(), key() | list()) :: value()

Reads the application environment at compilation time or raises.

This is the same as compile_env/3 but it raises an ArgumentError if the configuration is not available.