feat(socket.io-client): expose the standalone ESM bundle through the "./browser" subpath export

packages/socket.io-client/package.json

@@ -32,6 +32,10 @@
         "default": "./build/cjs/index.js"
       }
     },
+    "./browser": {
+      "types": "./build/esm/index.d.ts",
+      "default": "./dist/socket.io.esm.min.js"
+    },
     "./debug": {
       "import": {
         "types": "./build/esm/index.d.ts",

packages/socket.io-client/test/browser-export.ts

@@ -0,0 +1,34 @@
+import { existsSync, readFileSync } from "fs";
+import { createRequire } from "module";
+import { join } from "path";
+import expect = require("expect.js");
+
+// the "socket.io-client/browser" subpath export allows importing the
+// standalone ESM bundle directly (for example with Deno or in the browser),
+// without a bundler and without copying the bundle locally
+// see https://github.com/socketio/socket.io/issues/5383
+describe("browser export", () => {
+  const packageRoot = join(__dirname, "..");
+  const pkg = JSON.parse(
+    readFileSync(join(packageRoot, "package.json"), "utf8"),
+  );
+
+  it("should declare a ./browser subpath export", () => {
+    expect(pkg.exports["./browser"]).to.eql({
+      types: "./build/esm/index.d.ts",
+      default: "./dist/socket.io.esm.min.js",
+    });
+  });
+
+  it("should point to files that exist", () => {
+    const entry = pkg.exports["./browser"];
+    expect(existsSync(join(packageRoot, entry.default))).to.be(true);
+    expect(existsSync(join(packageRoot, entry.types))).to.be(true);
+  });
+
+  it("should be resolvable by its package name", () => {
+    const require = createRequire(join(packageRoot, "index.js"));
+    const resolved = require.resolve("socket.io-client/browser");
+    expect(resolved).to.be(join(packageRoot, "dist", "socket.io.esm.min.js"));
+  });
+});

packages/socket.io-client/test/index.ts

@@ -1,3 +1,4 @@
+import "./browser-export";
 import "./url";
 import "./connection";
 import "./socket";