Is there a way to use AVA with TypeScript + ESM without compile it?

[wellwelwel]

I'm trying to perform a simple error test:

npm i -D ava tsx

test/index.test.ts

import test from "ava";

test("Number should not be a text", (t) => {
  t.deepEqual("1", 1);
});

package.json

{
  "type": "module",
  "ava": {
    "files": [
      "test/**/*.test.ts"
    ],
    "extensions": {
      "ts": "module"
    },
    "nodeArguments": [
      "--import=tsx"
    ]
  },
  "devDependencies": {
    "ava": "^6.1.1",
    "tsx": "^4.7.1"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "target": "ESNext",
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "esModuleInterop": true
  }
}

---

The above test works if I change from:

- "ts": "module"

To:

+ "ts": "commonjs"

But, naturally, running it as CJS instead.

---

❌ Here's the error when running it as "module":

npx ava

  Uncaught exception in test/index.test.ts

  TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for ***/test/index.test.ts

  TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for ***/test/index.test.ts
      at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:160:9)
      at defaultGetFormat (node:internal/modules/esm/get_format:203:36)
      at defaultLoad (node:internal/modules/esm/load:143:22)
      at async ModuleLoader.load (node:internal/modules/esm/loader:403:7)
      at async ModuleLoader.moduleProvider (node:internal/modules/esm/loader:285:45)
      at async link (node:internal/modules/esm/module_job:76:21)

  ✘ test/index.test.ts exited with a non-zero exit code: 1
  ─

  1 uncaught exception

---

✅ And here's the file running successfully as "commonjs":

npx ava

  ✘ [fail]: Number should not be a text
  ─

  Number should not be a text

  test/index.test.ts:2

   1: import test from "ava";                     
   2:                                             
   3: test("Number should not be a text", (t) => {

  Difference (- actual, + expected):

  - '1'
  + 1

  › test/index.test.ts:2:847

  ─

  1 test failed

[wellwelwel]

I found a similar issue (not necessarily related), but it looks was closed without a conclusion, despite the PR #3192:

• Update TypeScript recipe for ESM support #2593

[novemberborn]

  TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for ***/test/index.test.ts

  TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for ***/test/index.test.ts
      at Object.getFileProtocolModuleFormat [as file:] (node:internal/modules/esm/get_format:160:9)
      at defaultGetFormat (node:internal/modules/esm/get_format:203:36)
      at defaultLoad (node:internal/modules/esm/load:143:22)
      at async ModuleLoader.load (node:internal/modules/esm/loader:403:7)
      at async ModuleLoader.moduleProvider (node:internal/modules/esm/loader:285:45)
      at async link (node:internal/modules/esm/module_job:76:21)

This stacktrace is internal to Node.js. My guess would be that the tsx loader isn't active. It may work for commonjs since AVA uses require() in that scenario, and maybe the loader does work there.

[wellwelwel]

Thanks, @novemberborn!

---

By removing tsx and keeping it as "commonjs", it stop to work and returns a common error of a "non-compiled" ts file:

  Uncaught exception in test/index.test.ts

  ***/test/index.test.ts:1
  import test from 'ava';
  ^^^^^^

  SyntaxError: Cannot use import statement outside a module

  ✘ test/index.test.ts exited with a non-zero exit code: 1
  ─

  1 uncaught exception

---

Do you think there is a way to reach out it (AVA with TypeScript + ESM without compile) using other loader or a different approach?

Seeing the discussions in PR #2593, I saw that the recommendation was to use tsx, but I also tried ts-node, without success.

[novemberborn]

I intentionally avoid this mess myself, using @ava/typescript and always running the compiler in a split tab in my terminal.

[wellwelwel]

By using @ava/typescript (independent of using tsx or not), it causes this error:

  Uncaught exception in test/index.test.ts

  TypeError: Cannot destructure property 'negotiateProtocol' of 'undefined' as it is undefined.

  TypeError: Cannot destructure property 'negotiateProtocol' of 'undefined' as it is undefined.
      at typescriptProvider (***/node_modules/@ava/typescript/index.js:77:45)
      at run (***/node_modules/ava/lib/worker/base.js:227:11)
      at async ***/node_modules/ava/lib/worker/base.js:281:2

  ✘ test/index.test.ts exited with a non-zero exit code: 1
  ─

  1 uncaught exception

---

I tried using the recommendations from README.md:

{
  "devDependencies": {
    "@ava/typescript": "^4.1.0",
    "ava": "^6.1.1"
  },
  "ava": {
    "files": [
      "test/**/*.test.ts"
    ],
    "require": [
      "@ava/typescript"
    ],
    "typescript": {
      "extensions": [
        "ts"
      ],
      "rewritePaths": {
        "test/": "build/"
      },
      "compile": false
    }
  }
}

---

@novemberborn, maybe should I open an Issue on https://github.com/avajs/typescript?

[wellwelwel]

For a better context, I was creating examples for the most popular Test Runners and how to reach out in the same result using them, including AVA:

# Comparing Test Runners

**Comparison using **Node.js**, **TypeScript** (_no compile_) and **ESM** to show a simple error test:**

- Let's starting from installation 🔬

• Then, the examples.

[novemberborn]

It's misconfigured. Don't add the require block, and you don't need to specify extensions either.

[wellwelwel]

I get it now, @ava/typescript is compiling it before to run.

I'll keep the AVA example as "commonjs", since the main idea is not to compile, and relate this discussion on it.

Thanks again, @novemberborn! 🚀

[wellwelwel]

I intentionally avoid this mess myself, using @ava/typescript and always running the compiler in a split tab in my terminal.

Regardless, I will mark it as the answer, since this problem does not belong to this repository.

@novemberborn, sorry for the inconvenience (and also, thanks!) 🙋🏻‍♂️

[tommy-mitchell]

I use tsimp with this exact configuration (from the recipes):

"ava": {
	"extensions": {
		"ts": "module"
	},
	"nodeArguments": [
		"--import=tsimp"
	]
}

[wellwelwel]

Thanks @tommy-mitchell 🩵

In fact now it works for both "commonjs" and "module" skipping extra configs 🧑🏻‍🎓✨

---

Note

• In a first moment, tsimp is compiling TypeScript to .tsimp dir even including noEmit to true, then I just followed the tsimp documentation:

Also, the following fields are always hard-coded by tsimp:

• outDir Because tsimp isn't a build tool, but rather a module
  importer, it doesn't actually write the emitted JavaScript to
  disk. (Ok, technically it does, but only as a cache.) So, the
  outDir is hard-coded to .tsimp-compiled, but this is never
  used.
• [...]
• noEmit is always set false, because the entire point is to
  get the JavaScript code for Node to run. That said, the "emit"
  is fully virtual, and nothing is written to disk (except to
  avoid compiling the same code multiple times).