add support for Yarn PnP

fixes #168

Co-authored-by: Maël Nison <nison.mael@gmail.com>

lib/PnpPlugin.js

@@ -0,0 +1,56 @@
+/*
+	MIT License http://www.opensource.org/licenses/mit-license.php
+	Author Maël Nison @arcanis
+*/
+
+"use strict";
+
+module.exports = class PnpPlugin {
+	constructor(source, pnpApi, target) {
+		this.source = source;
+		this.pnpApi = pnpApi;
+		this.target = target;
+	}
+
+	apply(resolver) {
+		const target = resolver.ensureHook(this.target);
+		resolver
+			.getHook(this.source)
+			.tapAsync("PnpPlugin", (request, resolveContext, callback) => {
+				const req = request.request;
+
+				// The trailing slash indicates to PnP that this value is a folder rather than a file
+				const issuer = `${request.path}/`;
+
+				let resolution;
+				try {
+					resolution = this.pnpApi.resolveToUnqualified(req, issuer, {
+						considerBuiltins: false
+					});
+				} catch (error) {
+					return callback(error);
+				}
+
+				if (resolution === req) return callback();
+
+				const obj = {
+					...request,
+					path: resolution,
+					request: undefined,
+					ignoreSymlinks: true
+				};
+				resolver.doResolve(
+					target,
+					obj,
+					`resolved by pnp to ${resolution}`,
+					resolveContext,
+					(err, result) => {
+						if (err) return callback(err);
+						if (result) return callback(null, result);
+						// Skip alternatives
+						return callback(null, null);
+					}
+				);
+			});
+	}
+};

lib/ResolverFactory.js

@@ -28,6 +28,7 @@ const UseFilePlugin = require("./UseFilePlugin");
 const AppendPlugin = require("./AppendPlugin");
 const ResultPlugin = require("./ResultPlugin");
 const UnsafeCachePlugin = require("./UnsafeCachePlugin");
+const PnpPlugin = require("./PnpPlugin");
 
 exports.createResolver = function(options) {
 	//// OPTIONS ////
@@ -61,6 +62,15 @@ exports.createResolver = function(options) {
 	// A list of module alias configurations or an object which maps key to value
 	let alias = options.alias || [];
 
+	// A PnP API that should be used - null is "never", undefined is "auto"
+	const pnpApi =
+		options.pnpApi === undefined
+			? process.versions.pnp
+				? // eslint-disable-next-line node/no-missing-require
+				  require("pnpapi")
+				: null
+			: options.pnpApi;
+
 	// Resolve symlinks to their symlinked location
 	const symlinks =
 		typeof options.symlinks !== "undefined" ? options.symlinks : true;
@@ -203,6 +213,9 @@ exports.createResolver = function(options) {
 	plugins.push(new JoinRequestPlugin("after-described-resolve", "relative"));
 
 	// module
+	if (pnpApi) {
+		plugins.push(new PnpPlugin("raw-module", pnpApi, "relative"));
+	}
 	modules.forEach(item => {
 		if (Array.isArray(item))
 			plugins.push(
@@ -328,7 +341,8 @@ exports.createResolver = function(options) {
 		plugins.push(new FileExistsPlugin("file", "existing-file"));
 
 		// existing-file
-		if (symlinks) plugins.push(new SymlinkPlugin("existing-file", "relative"));
+		if (symlinks)
+			plugins.push(new SymlinkPlugin("existing-file", "existing-file"));
 		plugins.push(new NextPlugin("existing-file", "resolved"));
 	}
 

lib/SymlinkPlugin.js

@@ -20,6 +20,7 @@ module.exports = class SymlinkPlugin {
 		resolver
 			.getHook(this.source)
 			.tapAsync("SymlinkPlugin", (request, resolveContext, callback) => {
+				if (request.ignoreSymlinks) return callback();
 				const pathsResult = getPaths(request.path);
 				const pathSeqments = pathsResult.seqments;
 				const paths = pathsResult.paths;

test/fixtures/pnp/pkg/package.json

@@ -0,0 +1,7 @@
+{
+  "main": "main.js",
+  "browser": {
+    "./package-alias/index.js": "./package-alias/browser.js",
+    "module": "pkg/dir/index"
+  }
+}

test/pnp.js

@@ -0,0 +1,137 @@
+const path = require("path");
+const fs = require("fs");
+require("should");
+const ResolverFactory = require("../lib/ResolverFactory");
+const CachedInputFileSystem = require("../lib/CachedInputFileSystem");
+
+const nodeFileSystem = new CachedInputFileSystem(fs, 4000);
+
+const fixture = path.resolve(__dirname, "fixtures", "pnp");
+
+let isAdmin = false;
+try {
+	fs.symlinkSync("dir", path.resolve(fixture, "pkg/symlink"), "dir");
+	isAdmin = true;
+} catch (e) {
+	// ignore
+}
+try {
+	fs.unlinkSync(path.resolve(fixture, "pkg/symlink"));
+} catch (e) {
+	isAdmin = false;
+	// ignore
+}
+
+describe("pnp", () => {
+	let pnpApi;
+	let resolver;
+	if (isAdmin) {
+		before(() => {
+			fs.symlinkSync("dir", path.resolve(fixture, "pkg/symlink"), "dir");
+		});
+		after(() => {
+			fs.unlinkSync(path.resolve(fixture, "pkg/symlink"));
+		});
+	}
+	beforeEach(() => {
+		pnpApi = {
+			mocks: new Map(),
+			resolveToUnqualified(request, issuer) {
+				if (pnpApi.mocks.has(request)) {
+					return pnpApi.mocks.get(request);
+				} else {
+					throw new Error(`No way`);
+				}
+			}
+		};
+		resolver = ResolverFactory.createResolver({
+			extensions: [".ts", ".js"],
+			aliasFields: ["browser"],
+			fileSystem: nodeFileSystem,
+			pnpApi
+		});
+	});
+	it("should resolve by going through the pnp api", done => {
+		pnpApi.mocks.set(
+			"pkg/dir/index.js",
+			path.resolve(fixture, "pkg/dir/index.js")
+		);
+		resolver.resolve({}, __dirname, "pkg/dir/index.js", {}, (err, result) => {
+			if (err) return done(err);
+			result.should.equal(path.resolve(fixture, "pkg/dir/index.js"));
+			done();
+		});
+	});
+	it("should resolve module names with package.json", done => {
+		pnpApi.mocks.set("pkg", path.resolve(fixture, "pkg"));
+		resolver.resolve({}, __dirname, "pkg", {}, (err, result) => {
+			if (err) return done(err);
+			result.should.equal(path.resolve(fixture, "pkg/main.js"));
+			done();
+		});
+	});
+	it("should resolve namespaced module names", done => {
+		pnpApi.mocks.set("@user/pkg", path.resolve(fixture, "pkg"));
+		resolver.resolve({}, __dirname, "@user/pkg", {}, (err, result) => {
+			if (err) return done(err);
+			result.should.equal(path.resolve(fixture, "pkg/main.js"));
+			done();
+		});
+	});
+	it(
+		"should not resolve symlinks",
+		isAdmin
+			? done => {
+					pnpApi.mocks.set("pkg/symlink", path.resolve(fixture, "pkg/symlink"));
+					resolver.resolve({}, __dirname, "pkg/symlink", {}, (err, result) => {
+						if (err) return done(err);
+						result.should.equal(path.resolve(fixture, "pkg/symlink/index.js"));
+						done();
+					});
+			  }
+			: undefined
+	);
+	it("should properly deal with other extensions", done => {
+		pnpApi.mocks.set(
+			"@user/pkg/typescript",
+			path.resolve(fixture, "pkg/typescript")
+		);
+		resolver.resolve(
+			{},
+			__dirname,
+			"@user/pkg/typescript",
+			{},
+			(err, result) => {
+				if (err) return done(err);
+				result.should.equal(path.resolve(fixture, "pkg/typescript/index.ts"));
+				done();
+			}
+		);
+	});
+	it("should properly deal package.json alias", done => {
+		pnpApi.mocks.set(
+			"pkg/package-alias",
+			path.resolve(fixture, "pkg/package-alias")
+		);
+		resolver.resolve({}, __dirname, "pkg/package-alias", {}, (err, result) => {
+			if (err) return done(err);
+			result.should.equal(
+				path.resolve(fixture, "pkg/package-alias/browser.js")
+			);
+			done();
+		});
+	});
+	it("should skip normal modules when pnp resolves", done => {
+		pnpApi.mocks.set("m1/a.js", path.resolve(fixture, "pkg/a.js"));
+		resolver.resolve(
+			{},
+			path.resolve(__dirname, "fixtures"),
+			"m1/a.js",
+			{},
+			(err, result) => {
+				if (!err) return done(new Error("Resolving should fail"));
+				done();
+			}
+		);
+	});
+});