Function generateImgAttrs

packages/next/src/shared/lib/get-img-props.ts:224–279

({
  config,
  src,
  unoptimized,
  width,
  quality,
  sizes,
  loader,
}: GenImgAttrsData)

}

function generateImgAttrs({
  config,
  src,
  unoptimized,
  width,
  quality,
  sizes,
  loader,
}: GenImgAttrsData): GenImgAttrsResult {
  if (unoptimized) {
    if (src.startsWith('/') && !src.startsWith('//')) {
      let deploymentId = getDeploymentId()
      if (deploymentId) {
        // We unfortunately can't easily use `new URL()` here, because it normalizes the URL which causes
        // double-encoding with the `encodeURIComponent(src)` below
        const qIndex = src.indexOf('?')
        if (qIndex !== -1) {
          const params = new URLSearchParams(src.slice(qIndex + 1))
          const srcDpl = params.get('dpl')
          if (!srcDpl) {
            // src is missing the dpl parameter, but we have a deploymentId, so add it to the src URL
            params.append('dpl', deploymentId)
            src = src.slice(0, qIndex) + '?' + params.toString()
          }
        } else {
          // src is missing the dpl parameter, but we have a deploymentId, so add it to the src URL
          src = src + `?dpl=${deploymentId}`
        }
      }
    }
    return { src, srcSet: undefined, sizes: undefined }
  }

  const { widths, kind } = getWidths(config, width, sizes)
  const last = widths.length - 1

  return {
    sizes: !sizes && kind === 'w' ? '100vw' : sizes,
    srcSet: widths
      .map(
        (w, i) =>
          `${loader({ config, src, quality, width: w })} ${
            kind === 'w' ? w : i + 1
          }${kind}`
      )
      .join(', '),

    // It's intended to keep `src` the last attribute because React updates
    // attributes in order. If we keep `src` the first one, Safari will
    // immediately start to fetch `src`, before `sizes` and `srcSet` are even
    // updated by React. That causes multiple unnecessary requests if `srcSet`
    // and `sizes` are defined.
    // This bug cannot be reproduced in Chrome or Firefox.
    src: loader({ config, src, quality, width: widths[last] }),
  }
}

/**