plugin.js

const {
  spawn
} = require('child_process');
const fs = require('fs');
const path = require('path');
const commandExistsSync = require('command-exists').sync;
const chalk = require('chalk');
const Watchpack = require('watchpack');

const error = msg => console.log(chalk.bold.red(msg));
const info = msg => console.log(chalk.bold.blue(msg));
// https://github.com/wasm-tool/wasm-pack-plugin/issues/58
const wasmPackPath = process.env["WASM_PACK_PATH"];

class WasmPackPlugin {
  constructor(options) {
    /**
     * In some cases Webpack will require the pkg entrypoint before it actually
     * exists. To mitigate that we are forcing a first compilation.
     *
     * See https://github.com/wasm-tool/wasm-pack-plugin/issues/15
     */
    this._ranInitialCompilation = false;
    this.crateDirectory = options.crateDirectory;
    this.forceWatch = options.forceWatch;
    this.forceMode = options.forceMode;
    this.extraArgs = (options.extraArgs || '').trim().split(' ').filter(x => x);
    this.outDir = options.outDir || "pkg";
    this.outName = options.outName || "index";
    this.watchDirectories = (options.watchDirectories || [])
      .concat(path.resolve(this.crateDirectory, 'src'));
    this.watchFiles = [path.resolve(this.crateDirectory, 'Cargo.toml')];

    this.wp = new Watchpack();
    this.isDebug = true;
    this.error = null;
  }

  apply(compiler) {
    this.isDebug = this.forceMode ? this.forceMode === "development" : compiler.options.mode === "development";

    // This fixes an error in Webpack where it cannot find
    // the `pkg/index.js` file if Rust compilation errors.
    this._makeEmpty();

    // force first compilation
    compiler.hooks.beforeCompile.tapPromise('WasmPackPlugin', () => {
      if (this._ranInitialCompilation === true) {
        return Promise.resolve();
      }

      this._ranInitialCompilation = true;

      return this._checkWasmPack()
        .then(() => {
          const shouldWatch = this.forceWatch || (this.forceWatch === undefined && compiler.watchMode);

          if (shouldWatch) {
            this.wp.watch(this.watchFiles, this.watchDirectories, Date.now() - 10000);

            this.wp.on('change', () => {
              this._compile(true);
            });
          }

          return this._compile(false);
        });
    });

    let first = true;

    compiler.hooks.thisCompilation.tap('WasmPackPlugin', (compilation) => {
      // Super hacky, needed to workaround a bug in Webpack which causes
      // thisCompilation to be triggered twice on the first compilation.
      if (first) {
        first = false;

      } else {
        // This is needed in order to gracefully handle errors in Webpack,
        // since Webpack has its own custom error system.
        if (this.error != null) {
          compilation.errors.push(this.error);
        }
      }
    });
  }

  _makeEmpty() {
    try {
      fs.mkdirSync(this.outDir);
    } catch (e) {
      if (e.code !== "EEXIST") {
        throw e;
      }
    }

    fs.writeFileSync(path.join(this.outDir, this.outName + ".js"), "");
  }

  _checkWasmPack() {
    info('🧐  Checking for wasm-pack...\n');

    if (wasmPackPath !== undefined) {
      info('✅  wasm-pack is installed; managed by another tool. \n');
      return Promise.resolve();
    } else if (commandExistsSync('wasm-pack')) {
      info('✅  wasm-pack is installed. \n');

      return Promise.resolve();
    } else {
      info('ℹ️  Installing wasm-pack \n');

      return runProcess('cargo', ['install', 'wasm-pack'], {});
    }
  }

  _compile(watching) {
    info(`ℹ️  Compiling your crate in ${this.isDebug ? 'development' : 'release'} mode...\n`);

    return fs.promises.stat(this.crateDirectory).then(stats => {
      if (!stats.isDirectory()) {
        throw new Error(`${this.crateDirectory} is not a directory`);
      }
    }).then(() => {
      return spawnWasmPack({
        outDir: this.outDir,
        outName: this.outName,
        isDebug: this.isDebug,
        cwd: this.crateDirectory,
        extraArgs: this.extraArgs,
      });
    }).then((detail) => {
      // This clears out the error when the compilation succeeds.
      this.error = null;

      if (detail) {
        info(detail);
      }

      info('✅  Your crate has been correctly compiled\n');
    })
    .catch((e) => {
      // Webpack has a custom error system, so we cannot return an
      // error directly, instead we need to trigger it later.
      this.error = e;

      if (watching) {
        // This is to trigger a recompilation so it displays the error message
        this._makeEmpty();
      }
    });
  }
}

function spawnWasmPack({
  outDir,
  outName,
  isDebug,
  cwd,
  extraArgs
}) {
  const bin = wasmPackPath || 'wasm-pack';

  const args = [
    '--verbose',
    'build',
    '--out-dir', outDir,
    '--out-name', outName,
    ...(isDebug ? ['--dev'] : []),
    ...extraArgs
  ];

  const options = {
    cwd,
    stdio: "inherit"
  };

  return runProcess(bin, args, options);
}

function runProcess(bin, args, options) {
  return new Promise((resolve, reject) => {
    const p = spawn(bin, args, options);

    p.on('close', code => {
      if (code === 0) {
        resolve();

      } else {
        reject(new Error("Rust compilation."));
      }
    });

    p.on('error', reject);
  });
}

module.exports = WasmPackPlugin;