warmup method

void warmup()

OPEN B.11 / U25 — Pre-builds the bridge + stdlib infrastructure so the first real execute/executeBundle call does not cold-start mid-test.

Why this exists

The first script run after a test harness' setUpAll historically flaked under host load because the interpreter infrastructure (extension finalization, the ~30 stdlib bridges, and the registered bridged-class/enum definitions) cold-started during that first build. The shipped reset API (resetScriptDeclarations) does not warm anything — it only evicts script declarations. This method pays that cold-start cost up front, before the first real build, so the first build behaves like a warm one.

What it warms

1. finalizeBridges — fires every queued extension callback (relaxers, interface proxies, generic constructors) and freezes the runner. After this the bridge surface is fully wired.
2. A throwaway global Environment built via _initEnvironment, which exercises the full Stdlib(...).register() + bridged-definition registration path that every build would otherwise pay on first run.

The runner has no Dart source parser (that lives in tom_d4rt_exec's D4rt, which warms the analyzer front-end in its own warmup), so this warms only the bridge/stdlib half — which is the portion the parser-less Flutter runtime (and the test app's /warmup endpoint) shares.

Idempotent and script-neutral: the warmup environment is discarded; it leaves no script declarations behind. The next real execute/executeBundle rebuilds a fresh environment as usual.

Implementation

void warmup() {
  finalizeBridges();
  // Step 8: build (and cache) the warm parent so the first real build does
  // not pay the stdlib + bridged-definition cost. _initEnvironment returns a
  // throwaway child chained off that parent; the next execute*/executeBundle*
  // call constructs its own fresh child off the same cached parent.
  final child = _initEnvironment();
  final parentEntries = child.enclosing?.values.length ?? 0;
  Logger.debug(
    '[D4rtRunner.warmup] Warmed bridge + stdlib infrastructure '
    '($parentEntries warm-parent baseline entries).',
  );
}