presets(vercel): allow overriding function config by route

[pi0]

Summary

Backport of 589e8ad (#4124) to v2.

Adds vercel.functionRules option for per-route serverless function configuration overrides. Routes matching functionRules get copied function directories (instead of symlinks) with merged .vc-config.json. Includes auto-derived consumer names for queue/v2beta triggers.

Usage

export default defineNitroConfig({
  vercel: {
    functionRules: {
      '/api/my-slow-routes/**': { maxDuration: 3600 },
      '/api/queues/fulfill-order': {
        experimentalTriggers: [{ type: 'queue/v2beta', topic: 'orders' }],
      },
    },
  },
})

Regression fixes

• Spread order: handler, launcherType, shouldAddHelpers, supportsResponseStreaming are now enforced after the user spread, so they can't be accidentally overridden via vercel.functions
• ISR route shadowing: functionRules patterns that overlap with ISR route rules are excluded from config.json routes, preventing ISR from being silently bypassed
• Array merge: defu merges arrays by default — overrides with array fields (e.g. experimentalTriggers) now fully replace the base config arrays instead of merging
• Leading slash normalization: functionRules pattern keys are normalized with a leading / to prevent broken output from normalizeRouteDest/normalizeRouteSrc
• ISR + functionRules: ISR function directories correctly receive merged functionRules overrides (e.g. regions) via createFunctionDirWithCustomConfig
• Observability route matching: use original route pattern (not PCRE regex) for radix3 matching, so functionRules wildcards correctly apply to dynamic observability routes
• Duplicate config.json entries: functionRules routes that already appear in observability routes are deduplicated in config.json

Test plan

• 57 vercel preset tests pass (55 existing + 2 new)
• 34 vercel-edge preset tests pass
• New tests for custom function directory creation, merged config, arbitrary fields, file copying, and base config isolation
• New test verifying ISR function directories receive functionRules overrides (regions)
• New test verifying wildcard functionRules apply to observability route directories (/api/storage/** → /api/storage/dev.func)

[vercel]

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Project	Deployment	Actions	Updated (UTC)
nitro.build	Ready	Preview, Comment	Apr 2, 2026 8:47am

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