Repository: fastify/fastify
File: fastify.js (JavaScript)

Code before:
        mustMatchWhenDerived: true,
        storage: options.versioning.storage,
        deriveConstraint: options.versioning.deriveVersion,
        validate (value) {
          if (typeof value !== 'string') {
            throw new FST_ERR_VERSION_CONSTRAINT_NOT_STR()
          }
        }
      }
    }
  }

  // Default router
  const router = buildRouting({
    config: {
      defaultRoute,
      onBadUrl,
      constraints,
      ignoreTrailingSlash: options.ignoreTrailingSlash || defaultInitOptions.ignoreTrailingSlash,
      ignoreDuplicateSlashes: options.ignoreDuplicateSlashes || defaultInitOptions.ignoreDuplicateSlashes,
      maxParamLength: options.maxParamLength || defaultInitOptions.maxParamLength,
      caseSensitive: options.caseSensitive,
      allowUnsafeRegex: options.allowUnsafeRegex || defaultInitOptions.allowUnsafeRegex,
      buildPrettyMeta: defaultBuildPrettyMeta,
      querystringParser: options.querystringParser,
      useSemicolonDelimiter: typeof options.useSemicolonDelimiter === 'boolean' ? options.useSemicolonDelimiter : defaultInitOptions.useSemicolonDelimiter
    }
  })

  // 404 router, used for handling encapsulated 404 handlers
  const fourOhFour = build404(options)

  // HTTP server and its handler
  const httpHandler = wrapRouting(router, options)

  // we need to set this before calling createServer
  options.http2SessionTimeout = initialConfig.http2SessionTimeout
  const { server, listen } = createServer(options, httpHandler)

  const serverHasCloseAllConnections = typeof server.closeAllConnections === 'function'
  const serverHasCloseIdleConnections = typeof server.closeIdleConnections === 'function'

  let forceCloseConnections = options.forceCloseConnections
  if (forceCloseConnections === 'idle' && !serverHasCloseIdleConnections) {
    throw new FST_ERR_FORCE_CLOSE_CONNECTIONS_IDLE_NOT_AVAILABLE()
  } else if (typeof forceCloseConnections !== 'boolean') {
    /* istanbul ignore next: only one branch can be valid in a given Node.js version */
    forceCloseConnections = serverHasCloseIdleConnections ? 'idle' : false
  }

  const keepAliveConnections = !serverHasCloseAllConnections && forceCloseConnections === true ? new Set() : noopSet()

Review comment (suggestion):
I guess you wanted to use the `??` operator?

```suggestion
      useSemicolonDelimiter: options.useSemicolonDelimiter ?? defaultInitOptions.useSemicolonDelimiter
```

Code after:
        mustMatchWhenDerived: true,
        storage: options.versioning.storage,
        deriveConstraint: options.versioning.deriveVersion,
        validate (value) {
          if (typeof value !== 'string') {
            throw new FST_ERR_VERSION_CONSTRAINT_NOT_STR()
          }
        }
      }
    }
  }

  // Default router
  const router = buildRouting({
    config: {
      defaultRoute,
      onBadUrl,
      constraints,
      ignoreTrailingSlash: options.ignoreTrailingSlash || defaultInitOptions.ignoreTrailingSlash,
      ignoreDuplicateSlashes: options.ignoreDuplicateSlashes || defaultInitOptions.ignoreDuplicateSlashes,
      maxParamLength: options.maxParamLength || defaultInitOptions.maxParamLength,
      caseSensitive: options.caseSensitive,
      allowUnsafeRegex: options.allowUnsafeRegex || defaultInitOptions.allowUnsafeRegex,
      buildPrettyMeta: defaultBuildPrettyMeta,
      querystringParser: options.querystringParser,
      useSemicolonDelimiter: options.useSemicolonDelimiter ?? defaultInitOptions.useSemicolonDelimiter
    }
  })

  // 404 router, used for handling encapsulated 404 handlers
  const fourOhFour = build404(options)

  // HTTP server and its handler
  const httpHandler = wrapRouting(router, options)

  // we need to set this before calling createServer
  options.http2SessionTimeout = initialConfig.http2SessionTimeout
  const { server, listen } = createServer(options, httpHandler)

  const serverHasCloseAllConnections = typeof server.closeAllConnections === 'function'
  const serverHasCloseIdleConnections = typeof server.closeIdleConnections === 'function'

  let forceCloseConnections = options.forceCloseConnections
  if (forceCloseConnections === 'idle' && !serverHasCloseIdleConnections) {
    throw new FST_ERR_FORCE_CLOSE_CONNECTIONS_IDLE_NOT_AVAILABLE()
  } else if (typeof forceCloseConnections !== 'boolean') {
    /* istanbul ignore next: only one branch can be valid in a given Node.js version */
    forceCloseConnections = serverHasCloseIdleConnections ? 'idle' : false
  }

  const keepAliveConnections = !serverHasCloseAllConnections && forceCloseConnections === true ? new Set() : noopSet()