Function resolveAssetUrlsInCss

packages/vite/src/node/plugins/css.ts:706–767

(
              chunkCSS: string,
              cssAssetName: string,
              originalFileName?: string,
            )

            // resolve asset URL placeholders to their built file URLs
            const resolveAssetUrlsInCss = (
              chunkCSS: string,
              cssAssetName: string,
              originalFileName?: string,
            ) => {
              const encodedPublicUrls = encodePublicUrlsInCSS(config)

              const relative = config.base === './' || config.base === ''
              const cssAssetDirname =
                encodedPublicUrls || relative
                  ? slash(getCssAssetDirname(cssAssetName, originalFileName))
                  : undefined

              const toRelative = (filename: string) => {
                // relative base + extracted CSS
                const relativePath = normalizePath(
                  path.relative(cssAssetDirname!, filename),
                )
                return relativePath[0] === '.'
                  ? relativePath
                  : './' + relativePath
              }

              // replace asset url references with resolved url.
              chunkCSS = chunkCSS.replace(
                assetUrlRE,
                (_, fileHash, postfix = '') => {
                  const filename = this.getFileName(fileHash) + postfix
                  chunk.viteMetadata!.importedAssets.add(cleanUrl(filename))
                  return encodeURIPath(
                    toOutputFilePathInCss(
                      filename,
                      'asset',
                      cssAssetName,
                      'css',
                      config,
                      toRelative,
                    ),
                  )
                },
              )
              // resolve public URL from CSS paths
              if (encodedPublicUrls) {
                const relativePathToPublicFromCSS = normalizePath(
                  path.relative(cssAssetDirname!, ''),
                )
                chunkCSS = chunkCSS.replace(publicAssetUrlRE, (_, hash) => {
                  const publicUrl = publicAssetUrlMap.get(hash)!.slice(1)
                  return encodeURIPath(
                    toOutputFilePathInCss(
                      publicUrl,
                      'public',
                      cssAssetName,
                      'css',
                      config,
                      () => `${relativePathToPublicFromCSS}/${publicUrl}`,
                    ),
                  )