Update Kotlin 1 -> 2 and support ES Modules

[SalvatoreT]

I borrowed the idea for appending the default export logic from this PR. https://github.com/cloudflare/kotlin-worker-hello-world/pull/5/files#diff-32a67597b31ada0ad6939d90a911ffc57238ecf93bd77a3fa110f7f62863c5b4R30-R51

Closes #4 #8

[StefanOltmann]

I didn't saw your PR when I created mine.
Your one looks more modern, so I just tried it.

Unfortunately wrangler dev doesn't work for me.
The resulting webpage crashes with this error:

ReferenceError {

  stack: 'ReferenceError: HelloWorker is not defined\n' +
  '    at Object.fetch (file:///C:/Users/Stefan/Downloads/kotlin-worker-hello-world-salvatoret-bump-kotlin-version/build/js/packages/kotlin-worker-hello-world/kotlin/kotlin-worker-hello-world.mjs:4:9)',
  message: 'HelloWorker is not defined',
  cause: undefined,
  name: 'ReferenceError',
}

Also, please consider removing the ./ in front of ./gradlew to make it work on Windows, too.

[SalvatoreT]

Unfortunately wrangler dev doesn't work for me.

I'm guessing yours didn't compile properly? I don't really have enough information.

It works fine for me!

❯ wrangler dev

 ⛅️ wrangler 4.33.2
───────────────────
[custom build] Running: ./gradlew :compileProductionExecutableKotlinJs
[custom build] Reusing configuration cache.
[custom build]
[custom build] > Task :checkKotlinGradlePluginConfigurationErrors SKIPPED
[custom build] > Task :jsProcessResources NO-SOURCE
[custom build] > Task :compileKotlinJs UP-TO-DATE
[custom build] > Task :jsMainClasses UP-TO-DATE
[custom build] > Task :compileProductionExecutableKotlinJs UP-TO-DATE
[custom build] > Task :jsProductionExecutableCompileSync UP-TO-DATE
[custom build]
[custom build] BUILD SUCCESSFUL in 296ms
[custom build] 3 actionable tasks: 3 up-to-date
[custom build] Configuration cache entry reused.
[custom build]
╭──────────────────────────────────────────────────────────────────────╮
│  [b] open a browser [d] open devtools [c] clear console [x] to exit  │
╰──────────────────────────────────────────────────────────────────────╯
The file src changed, restarting build...
[custom build] Running: ./gradlew :compileProductionExecutableKotlinJs
[custom build] Reusing configuration cache.
[custom build]
[custom build] > Task :checkKotlinGradlePluginConfigurationErrors SKIPPED
[custom build] > Task :jsProcessResources NO-SOURCE
[custom build] > Task :compileKotlinJs UP-TO-DATE
[custom build]
[custom build] > Task :jsMainClasses UP-TO-DATE
[custom build] > Task :compileProductionExecutableKotlinJs UP-TO-DATE
[custom build] > Task :jsProductionExecutableCompileSync UP-TO-DATE
[custom build]
[custom build] BUILD SUCCESSFUL in 363ms
[custom build] 3 actionable tasks: 3 up-to-date
[custom build]
[custom build]
[custom build] Configuration cache entry reused.
[custom build]
⎔ Starting local server...
[wrangler:info] Ready on http://localhost:8787
[wrangler:info] GET / 200 OK (3ms)
[wrangler:info] GET / 200 OK (2ms)
[wrangler:info] GET /favicon.ico 200 OK (2ms)

---

Also, please consider removing the ./ in front of ./gradlew to make it work on Windows, too.

Then it'll stop working on macOS. 😞

diff --git i/wrangler.toml w/wrangler.toml
index f8e675a..cc0129a 100644
--- i/wrangler.toml
+++ w/wrangler.toml
@@ -4,4 +4,4 @@ compatibility_date = "2025-08-24"
 main = "build/js/packages/kotlin-worker-hello-world/kotlin/kotlin-worker-hello-world.mjs"
 
 [build]
-command = "./gradlew :compileProductionExecutableKotlinJs"
\ No newline at end of file
+command = "gradlew :compileProductionExecutableKotlinJs"
\ No newline at end of file

results in

❯ wrangler dev

 ⛅️ wrangler 4.33.2
───────────────────
[custom build] Running: gradlew :compileProductionExecutableKotlinJs
[custom build] /bin/sh: gradlew: command not found
[custom build]
✘ [ERROR] Error: Command failed with exit code 127: gradlew :compileProductionExecutableKotlinJs

  /bin/sh: gradlew: command not found
      at makeError
  (/opt/homebrew/Cellar/cloudflare-wrangler/4.33.2/libexec/lib/node_modules/wrangler/wrangler-dist/cli.js:64909:18)
      at handlePromise
  (/opt/homebrew/Cellar/cloudflare-wrangler/4.33.2/libexec/lib/node_modules/wrangler/wrangler-dist/cli.js:65387:29)
      at process.processTicksAndRejections (node:internal/process/task_queues:105:5)
      at async runCustomBuild

[StefanOltmann]

Yes, the issue turned out to be that some names are hard-coded and depend on how the checkout name is.
It helps to set the root project name.

I did that now in https://github.com/StefanOltmann/cloudflare-steam-name-update-service and got it working.

Thank you.