Make Jest configs runnable scripts

Getting Jest to work with ESM modules has been painful, and the guide at https://jestjs.io/docs/ecmascript-modules doesn't seem to work when the Jest config is in a TypeScript file.

Since I'm stubborn, I decided to try to find a workaround, and I found this one! We make the config a runnable script that runs the Jest command, rather than relying on the Jest command to read the config. This is a bit funny, but it seems to work, because Jest requires configuration to be JSON-serializable: https://jestjs.io/docs/configuration and the command-line config option (https://jestjs.io/docs/cli#--configpath) accepts a JSON string!

Author: miorel

workspaces/adventure-pack/jest.config.js

@@ -0,0 +1,44 @@
+import type { Config } from "jest";
+
+const config: Config = {
+  preset: "ts-jest",
+  testEnvironment: "node",
+};
+
+export default config;
+
+// Hack to make this config runnable as a script, since the combination of
+// Jest, ESM, and a TypeScript config has been painful to get working otherwise.
+import("node:process").then(async ({ default: process }) => {
+  if (import.meta.filename !== process.argv[1]) {
+    return;
+  }
+
+  try {
+    const { spawnWithSafeStdio } = await import(
+      "@code-chronicles/util/spawnWithSafeStdio"
+    );
+    await spawnWithSafeStdio(
+      "jest",
+      ["--color", "-c", JSON.stringify(config), ...process.argv.slice(2)],
+      {
+        stdio: "inherit",
+        env: {
+          ...process.env,
+          NODE_OPTIONS: [
+            "--experimental-vm-modules",
+            process.env.NODE_OPTIONS?.trim(),
+          ]
+            .filter(Boolean)
+            .join(" "),
+        },
+      },
+    );
+  } catch (err) {
+    console.error(
+      (err as Record<string, unknown> | null | undefined)?.message ?? err,
+    );
+    // eslint-disable-next-line require-atomic-updates -- Updating `process.exitCode` on error is logical.
+    process.exitCode = 1;
+  }
+});

workspaces/adventure-pack/jest.config.ts

@@ -47,10 +47,10 @@
     "goodies:python3:test": "bash goodies/python3/test.sh",
     "goodies:typescript:format": "prettier --color --write goodies/typescript",
     "goodies:typescript:install": "yarn",
-    "goodies:typescript:test": "jest --color \"/goodies/typescript/\"",
+    "goodies:typescript:test": "tsx ./jest.config.ts \"/goodies/typescript/\"",
     "build-app": "tsx src/scripts/build/main.ts",
     "build-chrome-extension": "tsx src/scripts/build/buildChromeExtension.ts",
-    "package-goodies:test": "cross-env NODE_OPTIONS=\"--experimental-vm-modules\" jest --color --testPathIgnorePatterns=\"<rootDir>/goodies/\"",
+    "package-goodies:test": "tsx ./jest.config.ts --testPathIgnorePatterns=\"<rootDir>/goodies/\"",
     "format": "yarn goodies:java:format && yarn goodies:kotlin:format && yarn goodies:python3:format && yarn goodies:typescript:format && prettier --color --write .",
     "lint": "eslint --color --max-warnings=0 .",
     "postinstall": "yarn goodies:java:install && yarn goodies:kotlin:install && yarn goodies:python3:install",

workspaces/adventure-pack/package.json

@@ -0,0 +1,44 @@
+import type { Config } from "jest";
+
+const config: Config = {
+  preset: "ts-jest",
+  testEnvironment: "node",
+};
+
+export default config;
+
+// Hack to make this config runnable as a script, since the combination of
+// Jest, ESM, and a TypeScript config has been painful to get working otherwise.
+import("node:process").then(async ({ default: process }) => {
+  if (import.meta.filename !== process.argv[1]) {
+    return;
+  }
+
+  try {
+    const { spawnWithSafeStdio } = await import(
+      "@code-chronicles/util/spawnWithSafeStdio"
+    );
+    await spawnWithSafeStdio(
+      "jest",
+      ["--color", "-c", JSON.stringify(config), ...process.argv.slice(2)],
+      {
+        stdio: "inherit",
+        env: {
+          ...process.env,
+          NODE_OPTIONS: [
+            "--experimental-vm-modules",
+            process.env.NODE_OPTIONS?.trim(),
+          ]
+            .filter(Boolean)
+            .join(" "),
+        },
+      },
+    );
+  } catch (err) {
+    console.error(
+      (err as Record<string, unknown> | null | undefined)?.message ?? err,
+    );
+    // eslint-disable-next-line require-atomic-updates -- Updating `process.exitCode` on error is logical.
+    process.exitCode = 1;
+  }
+});

workspaces/util/jest.config.mts

@@ -19,7 +19,7 @@
   "scripts": {
     "format": "prettier --color --write .",
     "lint": "eslint --color --max-warnings=0 .",
-    "test": "jest --color .",
+    "test": "tsx ./jest.config.mts",
     "typecheck": "tsc --pretty --project ."
   },
   "dependencies": {
@@ -35,7 +35,7 @@
     "jest": "29.7.0",
     "prettier": "3.3.3",
     "ts-jest": "29.2.5",
-    "ts-node": "10.9.2",
+    "tsx": "4.19.1",
     "type-fest": "4.26.1",
     "typescript": "5.6.2"
   }

workspaces/util/jest.config.ts

@@ -1,27 +1,29 @@
 import process from "node:process";
 import { spawn, type SpawnOptions } from "node:child_process";
 
+// TODO: audit callsites since the behavior is changing
+
 export function spawnWithSafeStdio(
   command: string,
   args: readonly string[],
-  options?: Omit<SpawnOptions, "stdio">,
+  options?: SpawnOptions,
 ): Promise<void> {
   return new Promise((resolve, reject) => {
     const childProcess = spawn(command, args, {
-      ...options,
+      // When using "inherit" mode, it sometimes broke the interaction with
+      // the actions/github-script@v7 GitHub Action, so we default to piping.
+      stdio: ["ignore", "pipe", "pipe"],
 
       // Without a shell specified, many comands seem to fail to spawn on
       // Windows. I verified that it's not a PATH issue. It seems like it's
       // probably https://github.com/nodejs/node-v0.x-archive/issues/5841
       ...(process.platform === "win32" && { shell: options?.shell ?? "bash" }),
 
-      // When using "inherit" mode, it sometimes broke the interaction with
-      // the actions/github-script@v7 GitHub Action...
-      stdio: ["ignore", "pipe", "pipe"],
+      ...options,
     });
 
-    childProcess.stdout.pipe(process.stdout);
-    childProcess.stderr.pipe(process.stderr);
+    childProcess.stdout?.pipe(process.stdout);
+    childProcess.stderr?.pipe(process.stderr);
 
     childProcess.on("error", reject);
     childProcess.on("exit", (exitCode) => {