Add --experimental-vm-modules flag to bin/harper

[cb1kenobi]

When running harper dev from an app, it throws the following:

Error: node_vm_1.SourceTextModule is not a constructor
    at createModule (/Users/chris/projects/harper/security/jsLoader.ts:285:14)
    at async getOrCreateModule (/Users/chris/projects/harper/security/jsLoader.ts:235:18)
    at async loadModuleWithCache (/Users/chris/projects/harper/security/jsLoader.ts:245:18)
    at async loadModuleWithVM (/Users/chris/projects/harper/security/jsLoader.ts:349:22)
    at async scopedImport (/Users/chris/projects/harper/security/jsLoader.ts:93:11)
    at async loadComponent (/Users/chris/projects/harper/components/componentLoader.ts:498:28)
    at async loadComponent (/Users/chris/projects/harper/components/componentLoader.ts:337:26)
    at async Promise.all (index 0)
    at async loadRootComponents (/Users/chris/projects/harper/server/loadRootComponents.js:36:3)
    at async startHTTPThreads (/Users/chris/projects/harper/server/threads/socketRouter.ts:49:4)

The problem is vm.SourceTextModule is only available when --experimental-vm-modules is set. This flag is set when the worker is started, however the components (e.g. my app) is loaded on the main thread before start worker is called.

[kriszyp]

I am really curious how to reproduce this? resources.isWorker is supposed to be false on the main thread on line 392 here: https://github.com/HarperFast/harper/blob/main/components/componentLoader.ts#L392
Which is supposed to prevent any application code from running on the main thread. In fact, if you can get application code running on the main thread, that is real bug. That should only happen if you set the worker thread count to zero, which is supposed to enter a special "lite" mode (https://github.com/HarperFast/harper/blob/main/server/threads/socketRouter.ts#L45), which isn't really supported (other than for unit tests).

[cb1kenobi]

I ran npm create harper@latest, choose to NOT start harper after installing npm deps, cd into the project. Make sure your harper points to v5. I nuked my ~/harper dir. Run harper dev.

P.S. I'm working on fixing the tests.

[kriszyp]

Oh, I see, this is because extension modules are running on the main thread. I think this is root issue, and we should look at preventing this altogether.
And I thought you couldn't pass in node args in the header like this?
And can you file a ticket for the issue?

[kriszyp]

I think the correct syntax is:
#!/usr/bin/env -S node --experimental-vm-modules
But I have no idea if that is really cross-platform/OS safe.

[cb1kenobi]

-S isn't strictly necessary if there's only a single argument.

[kriszyp]

I think we want to disable VM loading in jsLoader.ts when this condition occurs, not exit.

[cb1kenobi]

I hear you. This is a toughy. If you run node dist/bin/harper.js, then it will have different behavior than if you run harper via npm or global link.

[cb1kenobi]

I will update this PR to:

• add the -S to the shebang
• remove the exit if --experimental-vm-modules flag is not set
• use the non-sandboxed js loader if vm modules are not available (which is what v4 does)