Slightly incorrect JS (breaks esbuild)

[IngwiePhoenix]

Describe the bug

Hello!

Basically:

PS C:\Users\Ingwie Phoenix\work\v-test> v -skip-unused -backend js -prod .\js_hello_world.v -o hello.js
PS C:\Users\Ingwie Phoenix\work\v-test> esbuild --minify --platform=browser --bundle hello.js --outfile=hello.min.js
✘ [ERROR] Cannot assign to "len" because it is a constant

    hello.js:3010:2:
      3010 │     len = arr.length
           ╵     ~~~

  The symbol "len" was declared a constant here:

    hello.js:3009:8:
      3009 │     const len = new int(new int(0));
           ╵           ~~~

✘ [ERROR] Could not resolve "os"

    hello.js:7:20:
      7 │ const $os = require("os");
        ╵                     ~~~~

  The package "os" wasn't found on the file system but is built into node. Are you trying to bundle
  for node? You can use "--platform=node" to do that, which will remove this error.

2 errors

Versions:

> v version
V 0.4.9 e9c2314
> esbuild --version
0.25.0

Wanted to try and use V to write my frontend instead of TypeScript and just threw some of my favorite tools at the output to see what would happen.

Reproduction Steps

1. Take examples/js_hello_world.v verbatim.
2. Compile using the js (also same for js_browser) backend to hello.js
3. Throw esbuild at it.

Commands are above in the snippet.

Expected Behavior

The browser has neither require() nor an os module. It just shouldn't be emitted, or a polyfill included.

Current Behavior

A call to require() is made although there shouldn't be one.

Also, as an aside, it attempts to modify a const, which it shouldn't. Make it let or var instead (probably the former)

Possible Solution

There should be some polyfills that you could use if you needed os support. I haven't looked at what exactly the issue is yet, though, nor which APIs are needed.

Additional Information/Context

Got none; just tried stuff out...

V version

V 0.4.9 e9c2314

Environment details (OS name and version, etc.)

Windows 10: Microsoft Windows [Version 10.0.19045.5440]

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[huly-for-github]

Connected to Huly®: V_0.6-22130

[spytheman]

Try using -b js_browser with V.

[spytheman]

-backend js / -b js generates code for Node afaik.

[JalonSolov]

From v help build-js output:

"Usage:
v -b js [-options] ['run'] <target.v|target_directory> [run options]

Note that js defaults to the node codegen backend but it's also possible to
pick another:

• js_browser - V outputs JS source code ready for the browser.
• js_node - V outputs JS source code to run with nodejs.
• js_freestanding - V outputs JS source code with no hard runtime dependency."

[IngwiePhoenix]

I did that - I mentioned that in the description. But, just in case:

PS C:\Users\Ingwie Phoenix\work\v-test> v -skip-unused -backend js_browser -prod .\js_hello_world.v -o hello.js
PS C:\Users\Ingwie Phoenix\work\v-test> esbuild --minify --platform=browser --bundle hello.js --outfile=hello.min.js
✘ [ERROR] Cannot assign to "len" because it is a constant

    hello.js:3010:2:
      3010 │     len = arr.length
           ╵     ~~~

  The symbol "len" was declared a constant here:

    hello.js:3009:8:
      3009 │     const len = new int(new int(0));
           ╵           ~~~

✘ [ERROR] Could not resolve "os"

    hello.js:7:20:
      7 │ const $os = require("os");
        ╵                     ~~~~

  The package "os" wasn't found on the file system but is built into node. Are you trying to bundle
  for node? You can use "--platform=node" to do that, which will remove this error.

2 errors

Ran v up just in case (now V 0.4.9 1274f46, timestamp: 2025-02-18 18:27:12 +0200) and got the same result.

[IngwiePhoenix]

And for completeness' sake:

PS C:\Users\Ingwie Phoenix\work\v-test> rm *.js
PS C:\Users\Ingwie Phoenix\work\v-test> v -skip-unused -backend js_freestanding -prod .\js_hello_world.v -o hello.js
PS C:\Users\Ingwie Phoenix\work\v-test> esbuild --minify --platform=browser --bundle hello.js --outfile=hello.min.js
✘ [ERROR] Cannot assign to "len" because it is a constant

    hello.js:3010:2:
      3010 │     len = arr.length
           ╵     ~~~

  The symbol "len" was declared a constant here:

    hello.js:3009:8:
      3009 │     const len = new int(new int(0));
           ╵           ~~~

✘ [ERROR] Could not resolve "os"

    hello.js:7:20:
      7 │ const $os = require("os");
        ╵                     ~~~~

  The package "os" wasn't found on the file system but is built into node. Are you trying to bundle
  for node? You can use "--platform=node" to do that, which will remove this error.

2 errors

[JalonSolov]

Perhaps the JS backend wasn't updated for the recent V change to make it invalid to have a variable shadow a const.

[IngwiePhoenix]

@JalonSolov That seems to be the case. Looking at the commits in that particular folder, I can tell it hasn't seen a whole lot of attention as of late. Rathe runfortunate, but it can't be helped I guess (unless someone goes to take care of it - for which I unfortunately don't have the time...)

I'll leave this ticket open for the case that someone wants to pick it up. ^^

[IngwiePhoenix]

I am quite late here, but I only saw the fix was implemented when I checked back manually. Re-ran the tests, and the esbuild part works now as expected, woohoo! =)

Now to go off and write HTMX/AlpineJS plugins in V... because I can