V2: Bump minimum supported TypeScript version to 4.9.5 (#1231)

.gitignore

@@ -2,5 +2,6 @@
 .wrangler
 node_modules
 /packages/*/dist
+/packages/typescript-compat/*/dist
 /packages/connect-web/conformance/logs/*
 packages/connect-web/local.log

README.md

@@ -88,7 +88,7 @@ be more than happy to chat!
 - [@connectrpc/connect-express](https://www.npmjs.com/package/@connectrpc/connect-express):
   Adds your services to an [Express](https://expressjs.com/) server.
 
-The libraries and the generated code are compatible with ES2017 and TypeScript 4.1.
+The libraries and the generated code are compatible with ES2017 and TypeScript 4.9.5.
 
 ## Ecosystem
 

package.json

@@ -12,7 +12,8 @@
     "packages/example",
     "packages/connect-migrate",
     "packages/connect-conformance",
-    "packages/connect-cloudflare"
+    "packages/connect-cloudflare",
+    "packages/typescript-compat/*"
   ],
   "scripts": {
     "all": "turbo run --ui tui build format test conformance bundle-size lint attw license-header",

packages/example/src/server.ts

@@ -21,7 +21,7 @@ import type {
   ConverseRequest,
 } from "./gen/eliza_pb.js";
 import * as esbuild from "esbuild";
-import http2 from "http2";
+import * as http2 from "http2";
 import { readFileSync } from "fs";
 import { stdout } from "process";
 

packages/typescript-compat/README.md

@@ -0,0 +1,47 @@
+# TypeScript compatibility tests
+
+Each package in this directory tests compatibility with a TypeScript version.
+
+Our compatibility tests use the default settings for `tsconfig.json` that are
+generated by running `tsc --init` (with a few minor exceptions).  As a result,
+for any version we support, we inherently support the default settings
+respective to that version of TypeScript.
+
+### Which versions are tested
+
+- the earliest TypeScript version we support
+- the latest patch release of all minor versions up to the current release
+
+### Adding a new version
+
+To add a new minor or major version of TypeScript to the tests, copy the directory
+with the latest version, and make the following updates:
+
+#### package.json
+
+- Set an appropriate "name" field, for example `"ts5.2.x"`.
+- Set the version constraint for the `typescript` dependency, for example `"5.2.x"`.
+- Set the version for the `@types/node` dependency. The package uses dist-tags
+  to tag releases for older TypeScript versions. You have to look up the
+  corresponding version number on https://www.npmjs.com/package/@types/node?activeTab=versions.
+
+Delete the `node_modules` directory in the package if it exists, and run `npm install`
+from the repository root.
+
+#### tsconfig.json
+
+Generate a new `tsconfig.json` with default values with `node_modules/.bin/tsc --init`,
+and merge it with the existing one:
+- We want to use the default target, module, and other settings.
+- We have to include the test sources.
+- We explicitly want to emit declaration and declaration maps, because some
+  transpilation issues only occur when emitting them.
+- We explicitly want to check libs.
+
+### Running and maintaining the tests
+
+Run `npx turbo run test -F './packages/typescript-compat/*'` to run all tests.
+
+Unfortunately, `npm` has no mechanism to pin to a dist-tag for `@types/node`,
+but the actual version is a moving target. It is necessary to manually verify
+that we still use appropriate versions.

packages/typescript-compat/v4.9.x/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "ts4.9",
+  "scripts": {
+    "test": "node_modules/.bin/tsc --outDir dist"
+  },
+  "dependencies": {
+    "@connectrpc/connect-conformance": "*",
+    "@connectrpc/example": "*",
+    "@types/node": "22.5.4",
+    "typescript": "4.9.x"
+  }
+}

packages/typescript-compat/v4.9.x/tsconfig.json

@@ -0,0 +1,24 @@
+{
+  "include": [
+    "../../connect-conformance/src/index.ts",
+    "../../example/src/**/*.ts"
+  ],
+  // These are the default compiler options for TypeScript v4.9.x, created
+  // with `tsc --init` (except where noted in comments below)
+  "compilerOptions": {
+    // By default, target is es5. For iterables, we need target 2015 or higher,
+    // or downLevelIteration.
+    "target": "es2015",
+    "module": "commonjs",
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "strict": true,
+    // To guard against regression and ensure we are remaining backwards
+    // compatible, set the skipLibCheck flag to false explicitly.
+    "skipLibCheck": false,
+    // Certain errors are only triggered by actually emitting declaration files,
+    // see https://github.com/bufbuild/protobuf-es/pull/398
+    "declaration": true,
+    "declarationMap": true
+  }
+}