Move transform call into printer preprocess step

This is functionally equivalent to running this during the `parse` step since it runs once before printing the whole AST.

Author: thecrypticace

src/create-plugin.ts

@@ -16,6 +16,11 @@ export function createPlugin(transforms: TransformOptions<any>[]) {
   let printers: Record<string, Init<Printer<any>>> = Object.create(null)
 
   for (let opts of transforms) {
+    // Even though we run the `transform` step during `printer.preprocess`
+    // we still have to override the parser as Prettier won't use the printer
+    // from a plugin that does not *also* define a parser:
+    //
+    // https://github.com/prettier/prettier/blob/f2cfef1ec2c20eb04d327cd70d98bd07f7d72f00/src/main/normalize-format-options.js#L66-L68
     for (let [name, meta] of Object.entries(opts.parsers)) {
       parsers[name] = async () => {
         let plugin = await loadPlugins(meta.load ?? opts.load ?? [])
@@ -34,7 +39,7 @@ export function createPlugin(transforms: TransformOptions<any>[]) {
 
     for (let [name, meta] of Object.entries(opts.printers ?? {})) {
       printers[name] = async () => {
-        let plugin = await loadPlugins(opts.load ?? [])
+        let plugin = await loadPlugins(meta.load ?? opts.load ?? [])
         let original = plugin.printers?.[name]
         if (!original) return
 
@@ -79,15 +84,7 @@ function createParser({ name, original, opts }: { name: string; original: Parser
     // for Prettier v2 but still work with v3.
     //
     // Currently only the Twig plugin requires this.
-    let ast = await original.parse(code, options, options)
-
-    await transformAst({
-      ast,
-      opts,
-      options,
-    })
-
-    return ast
+    return original.parse(code, options, options)
   }
 
   return parser
@@ -97,6 +94,25 @@ function createPrinter({ original, opts }: { original: Printer<any>; opts: Trans
   let printer: Printer<any> = { ...original }
 
   let reprint = opts.reprint
+  let transform = opts.transform
+
+  if (transform) {
+    let preprocess = original.preprocess ?? ((ast: any) => ast)
+
+    printer.preprocess = new Proxy(preprocess, {
+      async apply(target, thisArg, args) {
+        let [ast, options] = args as Parameters<NonNullable<typeof original.preprocess>>
+
+        await transformAst({
+          ast,
+          opts,
+          options,
+        })
+
+        return Reflect.apply(target, thisArg, args)
+      },
+    })
+  }
 
   // Hook into the preprocessing phase to load the config
   if (reprint) {

src/index.ts

@@ -1023,6 +1023,10 @@ let html = defineTransform<HtmlNode>({
     vue: { dynamicAttrs: [':class', 'v-bind:class'] },
   },
 
+  printers: {
+    html: {},
+  },
+
   transform: transformHtml,
 })
 
@@ -1041,6 +1045,10 @@ let glimmer = defineTransform<GlimmerNode>({
     glimmer: {},
   },
 
+  printers: {
+    glimmer: {},
+  },
+
   transform: transformGlimmer,
 })
 
@@ -1061,6 +1069,10 @@ let css = defineTransform<CssNode>({
     less: {},
   },
 
+  printers: {
+    postcss: {},
+  },
+
   transform: transformCss,
 })
 
@@ -1099,6 +1111,12 @@ let js = defineTransform<import('@babel/types').Node>({
     },
   },
 
+  printers: {
+    estree: { load: ['prettier/plugins/estree'] },
+    'estree-oxc': { load: ['@prettier/plugin-oxc'] },
+    'estree-hermes': { load: ['@prettier/plugin-hermes'] },
+  },
+
   transform: transformJavaScript,
 })
 
@@ -1161,6 +1179,10 @@ let astro = defineTransform<AstroNode>({
     astro: {},
   },
 
+  printers: {
+    astro: {},
+  },
+
   transform: transformAstro,
 })
 
@@ -1174,6 +1196,10 @@ let marko = defineTransform<MarkoNode>({
     marko: {},
   },
 
+  printers: {
+    'marko-ast': {},
+  },
+
   transform: transformMarko,
 })
 
@@ -1206,6 +1232,10 @@ let twig = defineTransform<TwigNode>({
     twig: {},
   },
 
+  printers: {
+    twig: {},
+  },
+
   transform: transformTwig,
 })
 
@@ -1222,6 +1252,10 @@ let pug = defineTransform<PugNode>({
     pug: {},
   },
 
+  printers: {
+    'pug-ast': {},
+  },
+
   transform: transformPug,
 })
 
@@ -1239,6 +1273,10 @@ let liquid = defineTransform<LiquidNode>({
 
   parsers: { 'liquid-html': {} },
 
+  printers: {
+    'liquid-html-ast': {},
+  },
+
   transform: transformLiquid,
 })
 

src/transform.ts

@@ -56,7 +56,15 @@ export interface TransformOptions<T> {
   /**
    * A list of supported parser names
    */
-  printers?: Record<string, {}>
+  printers?: Record<
+    string,
+    {
+      /**
+       * Load the given plugins for the parsers and printers
+       */
+      load?: string[]
+    }
+  >
 
   /**
    * Transform entire ASTs