Two-color reachability

Module: src/analyze/reachability.ts.

computeReachability runs a mark-and-sweep over the symbol graph twice — once in each “color” — so it can separate production-dead from truly dead.

function computeReachability(input: {
  nodes: SymbolNode[];
  edges: SymbolEdge[];
  prodEntries: Set<string>;
  testEntries: Set<string>;
  taintedFiles?: Set<string>;
}): ReachabilityResult[];

The two passes

1. Prod pass — BFS from prodEntries over prod edges only → reachedByProd.
2. Any pass — BFS from all entries over prod + test edges → reachedByAny.

Classification per node:

In reachedByProd	In reachedByAny	Result
✅	—	alive
❌	✅	test-only
❌	❌	dead

Seeds that are themselves node ids count as reached; module-file seeds reach the symbols referenced at their top level, which then chain transitively through symbol-to-symbol edges.

Taint

findTaintedFiles(sources) flags files containing dynamic dispatch that static analysis can’t follow — non-literal dynamic import(), eval, or computed member dispatch (obj[name]()). Each ReachabilityResult carries a tainted flag for nodes in those files. Taint doesn’t change reachability; it’s consumed by classification to downgrade a dead candidate to maybe.

Entries

prodEntries come from resolveProdEntries (src/engine/prod-entries.ts): package.json main/module/bin/exports plus conventional source entries (src/index.ts, etc.), kept only when they exist among scanned files. testEntries come from the framework plugins.