Error Conditions

DAG Restoration Failure

Condition: Corrupted or incompatible DAG file

Handling:

• Log warning
• Delete corrupt file
• Create new empty DAG
• Full rebuild triggered

Not Fatal: Compilation continues

Version Mismatch

Condition: DAG file has different version number

Handling:

• DAG discarded
• Full rebuild

Common Cause: rebar3 upgrade

Critical Metadata Mismatch

Condition: Compiler version or important options changed

Example: Erlang/OTP upgraded from 24 to 25

Handling:

• DAG discarded
• Full rebuild

Ensures: Artifacts always match current environment

Circular Dependencies (File-Level)

Condition: Files depend on each other in cycle

Detection: digraph_utils:topsort/1 fails during timestamp propagation

Handling:

• Timestamps may not propagate correctly
• Compilation may fail later
• Not specifically caught at DAG level