A templateUrl shared by two components only hot-updates one of them #445

Split out of a Codex review finding on #444. Pre-existing on main — not introduced by that PR.

Symptom

When two component .ts files declare the same external templateUrl, editing that template dispatches angular:component-update for only one of them. The other keeps rendering the old template.

Cause

resourceToComponent is single-valued, and the last transform wins:

// vite-plugin/index.ts:264-268
// Reverse mapping: resource file path → component file path. Multi-component
// files almost always use inline templates, so a single owner per resource is
// sufficient in practice; if a templateUrl/styleUrl is shared across multiple
// components in the same file, only one will receive the HMR event.
const resourceToComponent = new Map<string, string>()
...
// :814
resourceToComponent.set(normalizedDep, actualId)

handleHotUpdate then resolves one owner:

// :1051
const componentFile = resourceToComponent.get(normalizedFile)
if (componentFile && dispatchAllComponentsInFile(componentFile))

Which owner wins is a race — measured across 11 runs, alpha won 5 and beta won 6.

Measured

Two components, both templateUrl: './shared.html', both mounted, editing the template:

Never both. Note the reload on main in middlewareMode does not rescue the other component — Vite re-serves its .ts from the transform cache with the old template inlined.

#444 partially mitigates this: addWatchFile gives the template an importer edge to both owners, so both .ts modules are invalidated and a user-initiated refresh now fixes the stale one. On main it stayed stale until its .ts was touched or the server restarted.

Suggested fix

Mirror the shape styleComponentOwners already uses for styles — the plugin has the pattern, templates just do not use it:

1. Declare templateComponentOwners: Map<string, Set<string>> beside styleComponentOwners.
2. Prune it in transform, copying the styleComponentOwners prune.
3. Populate it inside the existing TEMPLATE_REGEX gate — no new branch.
4. Iterate the owner set in handleHotUpdate instead of resourceToComponent.get().

resourceToComponent should stay single-valued; widening it would reach into the shared style path for no gain.