Dedupe compiler DAG edge insertion for artifacts #2850
Merged
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Issue described at https://erlangforums.com/t/rebar3-is-taking-longer-to-compile-projects/3061/13
It appears that edge insertion with a label involved messes with the bag table and continuously inflates the size of a DAG after many runs. Since changes are propagated through a graph, frequent changes to often-included header files or parse transforms risk multiplying edge counts.
This little patch ensures that before inserting an artifact edge, we first look whether it already exists; if so we don't add it any further, but keep all other semantics the same.