Function warn

packages/runtime-core/src/warning.ts:35–79

(msg: string, ...args: any[])

let isWarning = false

export function warn(msg: string, ...args: any[]): void {
  if (isWarning) return
  isWarning = true

  // avoid props formatting or warn handler tracking deps that might be mutated
  // during patch, leading to infinite recursion.
  pauseTracking()

  const instance = stack.length ? stack[stack.length - 1].component : null
  const appWarnHandler = instance && instance.appContext.config.warnHandler
  const trace = getComponentTrace()

  if (appWarnHandler) {
    callWithErrorHandling(
      appWarnHandler,
      instance,
      ErrorCodes.APP_WARN_HANDLER,
      [
        // eslint-disable-next-line no-restricted-syntax
        msg + args.map(a => a.toString?.() ?? JSON.stringify(a)).join(''),
        instance && instance.proxy,
        trace
          .map(
            ({ vnode }) => `at <${formatComponentName(instance, vnode.type)}>`,
          )
          .join('\n'),
        trace,
      ],
    )
  } else {
    const warnArgs = [`[Vue warn]: ${msg}`, ...args]
    if (
      trace.length &&
      // avoid spamming console during tests
      !__TEST__
    ) {
      /* v8 ignore next 2 */
      warnArgs.push(`\n`, ...formatTrace(trace))
    }
    console.warn(...warnArgs)
  }

  resetTracking()
  isWarning = false
}

export function getComponentTrace(): ComponentTraceStack {
  let currentVNode: VNode | null = stack[stack.length - 1]