Function trigger

src/ui-server/api/when.ts:199–207

(caller, site)

      return (await callArgumentsForFile(file.abs, file.language, [key])).get(siteKey(key)) ?? null;
    },
    async trigger(caller, site) {
      // Not counted against the budget: the tree is already parsed for the
      // site's guards, and a trigger lookup is a walk up from one node.
      if (!site.line || !supportsBranchGuards(caller.language)) return null;
      const file = resolve(caller);
      if (!file) return null;
      const key = { line: site.line, column: typeof site.column === 'number' ? site.column : null };
      return (await triggersForFile(file.abs, file.language, [key])).get(siteKey(key)) ?? null;
    },
    async callSite(caller, site) {
      if (!site.line || sites >= maxSites || !supportsBranchGuards(caller.language)) return null;
      const file = resolve(caller);