Function compileToFunction

packages/vue/src/index.ts:30–102

(
  template: string | HTMLElement,
  options?: CompilerOptions,
)

const compileCache: Record<string, RenderFunction> = Object.create(null)

function compileToFunction(
  template: string | HTMLElement,
  options?: CompilerOptions,
): RenderFunction {
  if (!isString(template)) {
    if (template.nodeType) {
      template = template.innerHTML
    } else {
      __DEV__ && warn(`invalid template option: `, template)
      return NOOP
    }
  }

  const key = genCacheKey(template, options)
  const cached = compileCache[key]
  if (cached) {
    return cached
  }

  if (template[0] === '#') {
    const el = document.querySelector(template)
    if (__DEV__ && !el) {
      warn(`Template element not found or is empty: ${template}`)
    }
    // __UNSAFE__
    // Reason: potential execution of JS expressions in in-DOM template.
    // The user must make sure the in-DOM template is trusted. If it's rendered
    // by the server, the template should not contain any user data.
    template = el ? el.innerHTML : ``
  }

  const opts = extend(
    {
      hoistStatic: true,
      onError: __DEV__ ? onError : undefined,
      onWarn: __DEV__ ? e => onError(e, true) : NOOP,
    } as CompilerOptions,
    options,
  )

  if (!opts.isCustomElement && typeof customElements !== 'undefined') {
    opts.isCustomElement = tag => !!customElements.get(tag)
  }

  const { code } = compile(template, opts)

  function onError(err: CompilerError, asWarning = false) {
    const message = asWarning
      ? err.message
      : `Template compilation error: ${err.message}`
    const codeFrame =
      err.loc &&
      generateCodeFrame(
        template as string,
        err.loc.start.offset,
        err.loc.end.offset,
      )
    warn(codeFrame ? `${message}\n${codeFrame}` : message)