lukastaegert/assets.js

## assets.js
export const rollupLogo = "./logo.svg";

## index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <link rel="stylesheet" type="text/css" href="styles.css" />
    <title>Plugin demo</title>
  </head>
  <body>
    <script src="index.js" type="module"></script>
  </body>
</html>

## index.js
import { rollupLogo } from "./assets.js";

const image = document.createElement("img");
image.src = rollupLogo;
document.body.appendChild(image);

## logo.svg

      
Display the source blob

    
Display the rendered blob

    
    Raw
  

              logo.svg
            
          
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## package.json
{
  "type": "module",
  "scripts": {
    "build": "rollup -c"
  },
  "dependencies": {
    "libxmljs2": "^0.25.1",
    "rollup": "^2.6.0"
  }
}

## rollup-plugin-build-from-html.js
import * as fs from "fs";
import * as path from "path";
import libXml from "libxmljs2";

// This plugin takes the path of an HTML file, scans for script tags and emits
// those as chunks. Then it scans for stylesheets and emits those as assets. At
// last, it creates a rewritten HTML file with the paths to the new chunks and
// assets (by default containing content-hashed file names) and adds it to the
// bundle as well.
export default function buildFromHtml(htmlFile) {
  const fileName = path.resolve(htmlFile);
  const doc = libXml.parseHtml(fs.readFileSync(fileName, "utf8"));
  const scriptFileReferences = new Map();
  const styleFileReferences = new Map();

  return {
    name: "generate-html",

    buildStart() {
      for (const tag of doc.find("//script")) {
        scriptFileReferences.set(
          tag,
          this.emitFile({
            type: "chunk",
            id: tag.attr("src").value(),
          })
        );
      }
      for (const tag of doc.find("//link[@rel='stylesheet']")) {
        styleFileReferences.set(
          tag,
          this.emitFile({
            type: "asset",
            name: path.basename(tag.attr("href").value()),
            source: fs.readFileSync(
              path.resolve(path.dirname(fileName), tag.attr("href").value())
            ),
          })
        );
      }
    },

    generateBundle() {
      for (const [tag, referenceId] of scriptFileReferences) {
        tag.attr("src", this.getFileName(referenceId));
      }
      for (const [tag, referenceId] of styleFileReferences) {
        tag.attr("href", this.getFileName(referenceId));
      }
      this.emitFile({
        type: "asset",
        source: doc.toString(false),
        fileName: "index.html",
      });
    },
  };
}

## rollup-plugin-emit-assets-from-file.js
import fs from "fs";
import path from "path";
import { rollup } from "rollup";

// This plugin takes the path of a JavaScript file that exports some constants
// which are interpreted as relative paths to assets. These files are added to
// the Rollup bundle and the file is rewritten to point to the new assets (by
// default with content-hashed file names).
export default function emitAssetsFromFile(assetsFile) {
  const fileName = path.resolve(assetsFile);
  let assetFileFound = false;
  return {
    name: "emit-assets",

    async load(id) {
      if (id === fileName) {
        assetFileFound = true;
        // This will only run if you are using Node 13+ and either the fileName
        // has an .mjs extension or you have "type": "module" in your
        // package.json. Otherwise replace import with getExportsFromFile
        // below.
        // const assets = await getExportsFromFile(fileName);
        const assets = await import(fileName);
        return Object.keys(assets)
          .map((assetKey) => {
            const assetFileName = path.resolve(assets[assetKey]);
            return `export const ${assetKey} = import.meta.ROLLUP_FILE_URL_${this.emitFile(
              {
                type: "asset",
                source: fs.readFileSync(path.resolve(assetFileName)),
                name: path.basename(assetFileName),
              }
            )};`;
          })
          .join("\n");
      }
    },

    buildEnd() {
      if (assetFileFound === false) {
        throw new Error(
          `Expected assets file "${fileName}" was not part of the module graph.`
        );
      }
    },
  };
}

// Helper to convert an ESM file to CJS, turn it into a function and run it to
// get its exports.
async function getExportsFromFile(fileName) {
  const getAssets = new Function(
    "module",
    "exports",
    (
      await (await rollup({ input: fileName })).generate({ format: "cjs" })
    ).output[0].code
  );
  const module = { exports: {} };
  getAssets(module, module.exports);
  return module.exports;
}

## rollup.config.mjs
import buildFromHtml from "./rollup-plugin-build-from-html.js";
import emitAssetsFromFile from "./rollup-plugin-emit-assets-from-file.js";

// See how we do not need an `input` option here at all!
// All chunks are created from the HTML file.
export default {
  output: {
    dir: "dist",
    format: "esm",
  },
  plugins: [buildFromHtml("index.html"), emitAssetsFromFile("assets.js")],
};

## styles.css
body {
  color: blue;
}
	<!DOCTYPE html>
	<html lang="en">
	<head>
	<link rel="stylesheet" type="text/css" href="styles.css" />
	<title>Plugin demo</title>
	</head>
	<body>
	<script src="index.js" type="module"></script>
	</body>
	</html>
	import { rollupLogo } from "./assets.js";

	const image = document.createElement("img");
	image.src = rollupLogo;
	document.body.appendChild(image);
	{
	"type": "module",
	"scripts": {
	"build": "rollup -c"
	},
	"dependencies": {
	"libxmljs2": "^0.25.1",
	"rollup": "^2.6.0"
	}
	}
	import * as fs from "fs";
	import * as path from "path";
	import libXml from "libxmljs2";

	// This plugin takes the path of an HTML file, scans for script tags and emits
	// those as chunks. Then it scans for stylesheets and emits those as assets. At
	// last, it creates a rewritten HTML file with the paths to the new chunks and
	// assets (by default containing content-hashed file names) and adds it to the
	// bundle as well.
	export default function buildFromHtml(htmlFile) {
	const fileName = path.resolve(htmlFile);
	const doc = libXml.parseHtml(fs.readFileSync(fileName, "utf8"));
	const scriptFileReferences = new Map();
	const styleFileReferences = new Map();

	return {
	name: "generate-html",

	buildStart() {
	for (const tag of doc.find("//script")) {
	scriptFileReferences.set(
	tag,
	this.emitFile({
	type: "chunk",
	id: tag.attr("src").value(),
	})
	);
	}
	for (const tag of doc.find("//link[@rel='stylesheet']")) {
	styleFileReferences.set(
	tag,
	this.emitFile({
	type: "asset",
	name: path.basename(tag.attr("href").value()),
	source: fs.readFileSync(
	path.resolve(path.dirname(fileName), tag.attr("href").value())
	),
	})
	);
	}
	},

	generateBundle() {
	for (const [tag, referenceId] of scriptFileReferences) {
	tag.attr("src", this.getFileName(referenceId));
	}
	for (const [tag, referenceId] of styleFileReferences) {
	tag.attr("href", this.getFileName(referenceId));
	}
	this.emitFile({
	type: "asset",
	source: doc.toString(false),
	fileName: "index.html",
	});
	},
	};
	}
	import fs from "fs";
	import path from "path";
	import { rollup } from "rollup";

	// This plugin takes the path of a JavaScript file that exports some constants
	// which are interpreted as relative paths to assets. These files are added to
	// the Rollup bundle and the file is rewritten to point to the new assets (by
	// default with content-hashed file names).
	export default function emitAssetsFromFile(assetsFile) {
	const fileName = path.resolve(assetsFile);
	let assetFileFound = false;
	return {
	name: "emit-assets",

	async load(id) {
	if (id === fileName) {
	assetFileFound = true;
	// This will only run if you are using Node 13+ and either the fileName
	// has an .mjs extension or you have "type": "module" in your
	// package.json. Otherwise replace import with getExportsFromFile
	// below.
	// const assets = await getExportsFromFile(fileName);
	const assets = await import(fileName);
	return Object.keys(assets)
	.map((assetKey) => {
	const assetFileName = path.resolve(assets[assetKey]);
	return `export const ${assetKey} = import.meta.ROLLUP_FILE_URL_${this.emitFile(
	{
	type: "asset",
	source: fs.readFileSync(path.resolve(assetFileName)),
	name: path.basename(assetFileName),
	}
	)};`;
	})
	.join("\n");
	}
	},

	buildEnd() {
	if (assetFileFound === false) {
	throw new Error(
	`Expected assets file "${fileName}" was not part of the module graph.`
	);
	}
	},
	};
	}

	// Helper to convert an ESM file to CJS, turn it into a function and run it to
	// get its exports.
	async function getExportsFromFile(fileName) {
	const getAssets = new Function(
	"module",
	"exports",
	(
	await (await rollup({ input: fileName })).generate({ format: "cjs" })
	).output[0].code
	);
	const module = { exports: {} };
	getAssets(module, module.exports);
	return module.exports;
	}
	import buildFromHtml from "./rollup-plugin-build-from-html.js";
	import emitAssetsFromFile from "./rollup-plugin-emit-assets-from-file.js";

	// See how we do not need an `input` option here at all!
	// All chunks are created from the HTML file.
	export default {
	output: {
	dir: "dist",
	format: "esm",
	},
	plugins: [buildFromHtml("index.html"), emitAssetsFromFile("assets.js")],
	};