Compilation Order Determination

Purpose

The compilation order determination stage takes the list of resolved dependencies and project applications and determines the correct sequence in which they must be compiled. This stage uses graph-based topological sorting to ensure that each application is compiled after all of its dependencies, preventing compilation errors due to missing dependencies. This applies to both dependency compilation and project application compilation separately.

When It Executes

This stage executes within the compile provider in two distinct contexts:

1. Dependency Compilation: During Dependency Resolution & Locking, the find_cycles/1 function determines the order for dependencies
2. Project App Compilation: In rebar_prv_compile:do/1, the compile_order/1 function determines order for project applications

Prerequisites

• Dependencies resolved with complete dependency information
• Project applications discovered with metadata
• Application dependencies extracted (both runtime applications and build-time deps)
• No circular dependencies (or detection ready to report them)

Outputs

• Topologically sorted list of applications
• Dependencies listed before dependents
• Error if circular dependencies detected
• Order ready for sequential compilation