viteLegacyPlugin() — vite Function Reference

Source Code

packages/plugin-legacy/src/index.ts lines 145–786

function viteLegacyPlugin(options: Options = {}): Plugin[] {
  let config: ResolvedConfig
  let targets: Options['targets']
  const modernTargets: Options['modernTargets'] =
    options.modernTargets || modernTargetsBabel

  const genLegacy = options.renderLegacyChunks !== false
  const genModern = options.renderModernChunks !== false
  if (!genLegacy && !genModern) {
    throw new Error(
      '`renderLegacyChunks` and `renderModernChunks` cannot be both false',
    )
  }

  const debugFlags = (process.env.DEBUG || '').split(',')
  const isDebug =
    debugFlags.includes('vite:*') || debugFlags.includes('vite:legacy')

  const assumptions = options.assumptions || {}

  const facadeToLegacyChunkMap = new Map()
  const facadeToLegacyPolyfillMap = new Map()
  const facadeToModernPolyfillMap = new Map()
  const modernPolyfills = new Set<string>()
  const legacyPolyfills = new Set<string>()
  // When discovering polyfills in `renderChunk`, the hook may be non-deterministic, so we group the
  // modern and legacy polyfills in a sorted chunks map for each rendered outputs before merging them.
  const outputToChunkFileNameToPolyfills = new WeakMap<
    Rollup.NormalizedOutputOptions,
    Map<string, { modern: Set<string>; legacy: Set<string> }> | null
  >()

  if (Array.isArray(options.modernPolyfills) && genModern) {
    options.modernPolyfills.forEach((i) => {
      modernPolyfills.add(
        i.includes('/') ? `core-js/${i}` : `core-js/modules/${i}.js`,
      )
    })
  }
  if (Array.isArray(options.additionalModernPolyfills)) {
    options.additionalModernPolyfills.forEach((i) => {
      modernPolyfills.add(i)
    })
  }
  if (Array.isArray(options.polyfills)) {
    options.polyfills.forEach((i) => {
      if (i.startsWith(`regenerator`)) {
        legacyPolyfills.add(`regenerator-runtime/runtime.js`)
      } else {
        legacyPolyfills.add(
          i.includes('/') ? `core-js/${i}` : `core-js/modules/${i}.js`,
        )
      }
    })
  }
  if (Array.isArray(options.additionalLegacyPolyfills)) {
    options.additionalLegacyPolyfills.forEach((i) => {
      legacyPolyfills.add(i)
    })
  }

  let overriddenBuildTarget = false
  let overriddenBuildTargetOnlyModern = false
  let overriddenDefaultModernTargets = false
  const legacyConfigPlugin: Plugin = {
    name: 'vite:legacy-config',

    async config(config, env) {
      if (env.command === 'build' && !config.build?.ssr) {
        if (!config.build) {
          config.build = {}
        }

        if (genLegacy && !config.build.cssTarget) {
          // Hint for esbuild that we are targeting legacy browsers when minifying CSS.
          // Full CSS compat table available at https://github.com/evanw/esbuild/blob/78e04680228cf989bdd7d471e02bbc2c8d345dc9/internal/compat/css_table.go
          // But note that only the `HexRGBA` feature affects the minify outcome.
          // HSL & rebeccapurple values will be minified away regardless the target.
          // So targeting `chrome61` suffices to fix the compatibility issue.
          config.build.cssTarget = 'chrome61'
        }