react/packages/react-server-dom-webpack/src/ReactFlightWebpackPlugin.js

/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

import {join} from 'path';
import {pathToFileURL} from 'url';

import asyncLib from 'neo-async';

import ModuleDependency from 'webpack/lib/dependencies/ModuleDependency';
import NullDependency from 'webpack/lib/dependencies/NullDependency';
import AsyncDependenciesBlock from 'webpack/lib/AsyncDependenciesBlock';
import Template from 'webpack/lib/Template';

class ClientReferenceDependency extends ModuleDependency {
  constructor(request) {
    super(request);
  }

  get type() {
    return 'client-reference';
  }
}

// This is the module that will be used to anchor all client references to.
// I.e. it will have all the client files as async deps from this point on.
// We use the Flight client implementation because you can't get to these
// without the client runtime so it's the first time in the loading sequence
// you might want them.
const clientFileName = require.resolve('../');

type ClientReferenceSearchPath = {
  directory: string,
  recursive?: boolean,
  include: RegExp,
  exclude?: RegExp,
};

type ClientReferencePath = string | ClientReferenceSearchPath;

type Options = {
  isServer: boolean,
  clientReferences?: ClientReferencePath | $ReadOnlyArray<ClientReferencePath>,
  chunkName?: string,
  manifestFilename?: string,
};

const PLUGIN_NAME = 'React Server Plugin';

export default class ReactFlightWebpackPlugin {
  clientReferences: $ReadOnlyArray<ClientReferencePath>;
  chunkName: string;
  manifestFilename: string;

  constructor(options: Options) {
    if (!options || typeof options.isServer !== 'boolean') {
      throw new Error(
        PLUGIN_NAME + ': You must specify the isServer option as a boolean.',
      );
    }
    if (options.isServer) {
      throw new Error('TODO: Implement the server compiler.');
    }
    if (!options.clientReferences) {
      this.clientReferences = [
        {
          directory: '.',
          recursive: true,
          include: /\.client\.(js|ts|jsx|tsx)$/,
        },
      ];
    } else if (
      typeof options.clientReferences === 'string' ||
      !Array.isArray(options.clientReferences)
    ) {
      this.clientReferences = [(options.clientReferences: $FlowFixMe)];
    } else {
      this.clientReferences = options.clientReferences;
    }
    if (typeof options.chunkName === 'string') {
      this.chunkName = options.chunkName;
      if (!/\[(index|request)\]/.test(this.chunkName)) {
        this.chunkName += '[index]';
      }
    } else {
      this.chunkName = 'client[index]';
    }
    this.manifestFilename =
      options.manifestFilename || 'react-client-manifest.json';
  }

  apply(compiler: any) {
    let resolvedClientReferences;
    const run = (params, callback) => {
      // First we need to find all client files on the file system. We do this early so
      // that we have them synchronously available later when we need them. This might
      // not be needed anymore since we no longer need to compile the module itself in
      // a special way. So it's probably better to do this lazily and in parallel with
      // other compilation.
      const contextResolver = compiler.resolverFactory.get('context', {});
      this.resolveAllClientFiles(
        compiler.context,
        contextResolver,
        compiler.inputFileSystem,
        compiler.createContextModuleFactory(),
        (err, resolvedClientRefs) => {
          if (err) {
            callback(err);
            return;
          }
          resolvedClientReferences = resolvedClientRefs;
          callback();
        },
      );
    };

    compiler.hooks.run.tapAsync(PLUGIN_NAME, run);
    compiler.hooks.watchRun.tapAsync(PLUGIN_NAME, run);
    compiler.hooks.compilation.tap(
      PLUGIN_NAME,
      (compilation, {normalModuleFactory}) => {
        compilation.dependencyFactories.set(
          ClientReferenceDependency,
          normalModuleFactory,
        );
        compilation.dependencyTemplates.set(
          ClientReferenceDependency,
          new NullDependency.Template(),
        );

        compilation.hooks.buildModule.tap(PLUGIN_NAME, module => {
          // We need to add all client references as dependency of something in the graph so
          // Webpack knows which entries need to know about the relevant chunks and include the
          // map in their runtime. The things that actually resolves the dependency is the Flight
          // client runtime. So we add them as a dependency of the Flight client runtime.
          // Anything that imports the runtime will be made aware of these chunks.
          // TODO: Warn if we don't find this file anywhere in the compilation.
          if (module.resource !== clientFileName) {
            return;
          }
          if (resolvedClientReferences) {
            for (let i = 0; i < resolvedClientReferences.length; i++) {
              const dep = resolvedClientReferences[i];
              const chunkName = this.chunkName
                .replace(/\[index\]/g, '' + i)
                .replace(/\[request\]/g, Template.toPath(dep.userRequest));

              const block = new AsyncDependenciesBlock(
                {
                  name: chunkName,
                },
                module,
                null,
                dep.require,
              );
              block.addDependency(dep);
              module.addBlock(block);
            }
          }
        });
      },
    );

    compiler.hooks.emit.tap(PLUGIN_NAME, compilation => {
      const json = {};
      compilation.chunkGroups.forEach(chunkGroup => {
        const chunkIds = chunkGroup.chunks.map(c => c.id);

        function recordModule(id, mod) {
          // TODO: Hook into deps instead of the target module.
          // That way we know by the type of dep whether to include.
          // It also resolves conflicts when the same module is in multiple chunks.
          if (!/\.client\.js$/.test(mod.resource)) {
            return;
          }
          const moduleExports = {};
          ['', '*'].concat(mod.buildMeta.providedExports).forEach(name => {
            moduleExports[name] = {
              id: id,
              chunks: chunkIds,
              name: name,
            };
          });
          const href = pathToFileURL(mod.resource).href;
          if (href !== undefined) {
            json[href] = moduleExports;
          }
        }

        chunkGroup.chunks.forEach(chunk => {
          chunk.getModules().forEach(mod => {
            recordModule(mod.id, mod);
            // If this is a concatenation, register each child to the parent ID.
            if (mod.modules) {
              mod.modules.forEach(concatenatedMod => {
                recordModule(mod.id, concatenatedMod);
              });
            }
          });
        });
      });
      const output = JSON.stringify(json, null, 2);
      compilation.assets[this.manifestFilename] = {
        source() {
          return output;
        },
        size() {
          return output.length;
        },
      };
    });
  }

  // This attempts to replicate the dynamic file path resolution used for other wildcard
  // resolution in Webpack is using.
  resolveAllClientFiles(
    context: string,
    contextResolver: any,
    fs: any,
    contextModuleFactory: any,
    callback: (
      err: null | Error,
      result?: $ReadOnlyArray<ClientReferenceDependency>,
    ) => void,
  ) {
    asyncLib.map(
      this.clientReferences,
      (
        clientReferencePath: string | ClientReferenceSearchPath,
        cb: (
          err: null | Error,
          result?: $ReadOnlyArray<ClientReferenceDependency>,
        ) => void,
      ): void => {
        if (typeof clientReferencePath === 'string') {
          cb(null, [new ClientReferenceDependency(clientReferencePath)]);
          return;
        }
        const clientReferenceSearch: ClientReferenceSearchPath = clientReferencePath;
        contextResolver.resolve(
          {},
          context,
          clientReferencePath.directory,
          {},
          (err, resolvedDirectory) => {
            if (err) return cb(err);
            const options = {
              resource: resolvedDirectory,
              resourceQuery: '',
              recursive:
                clientReferenceSearch.recursive === undefined
                  ? true
                  : clientReferenceSearch.recursive,
              regExp: clientReferenceSearch.include,
              include: undefined,
              exclude: clientReferenceSearch.exclude,
            };
            contextModuleFactory.resolveDependencies(
              fs,
              options,
              (err2: null | Error, deps: Array<ModuleDependency>) => {
                if (err2) return cb(err2);
                const clientRefDeps = deps.map(dep => {
                  const request = join(resolvedDirectory, dep.request);
                  const clientRefDep = new ClientReferenceDependency(request);
                  clientRefDep.userRequest = dep.userRequest;
                  return clientRefDep;
                });
                cb(null, clientRefDeps);
              },
            );
          },
        );
      },
      (
        err: null | Error,
        result: $ReadOnlyArray<$ReadOnlyArray<ClientReferenceDependency>>,
      ): void => {
        if (err) return callback(err);
        const flat = [];
        for (let i = 0; i < result.length; i++) {
          flat.push.apply(flat, result[i]);
        }
        callback(null, flat);
      },
    );
  }
}