Site is broken b/c of JS stack overflow

[armanbilge]

As reported by discord friends.

Linking to:

• Can't find variable: mdoc_js_run0 on iOS scalameta/mdoc#577
• mdoc.js and README.md.js scripts included twice in the page scalameta/mdoc#579

[armanbilge]

Some progress on this: I suspect the problem comes from the README.md.js file, where mdoc_js_run0 is defined:
https://http4s.github.io/http4s-dom/README.md.js
https://raw.githubusercontent.com/http4s/http4s-dom/d7a56a67ddca8b67b2e31da74d96c567b46ad898/README.md.js

Specifically, I think the maximum call stack size is being exceeded while running that file, causing it to fail, and that variable to be undefined.

To test this, I tried running that file with Node.js:

node --stack_size=500 README.md.js
vm.js:74
      super(code,
      ^

RangeError: Maximum call stack size exceeded
    at new Script (vm.js:74:7)
    at createScript (vm.js:246:10)
    at Object.runInThisContext (vm.js:298:10)
    at Module._compile (internal/modules/cjs/loader.js:657:28)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)
    at Module.load (internal/modules/cjs/loader.js:599:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)
    at startup (internal/bootstrap/node.js:236:19)

Increasing the stack size to 600 enables the file to load without problem.

So, the stack size on iOS Safari must be smaller than 600 and generally smaller than other browsers.

The remaining question is, which part of the Scala.js/mdoc.js/CE3/fs2/http4s stack is specifically to blame for this 😉

[armanbilge]

I wouldn't be shocked if MimeDB is to blame for this too ...

[armanbilge]

And here's a report from Firefox on macOS desktop ...

[armanbilge]

Here's another interesting twist: if the README.md.js is generated with fastOptJS instead of fullOptJS then I can lower the stack size to much more reasonable numbers without problem.

node --stack_size=80 mdocs/target/mdoc/README.md.js

So, the problem is specific to fullOptJS.

Next bit of trickyness, is to tease apart SJS full optimization phase from the Google Closure Compiler phase.

[armanbilge]

Next bit of trickyness, is to tease apart SJS full optimization phase from the Google Closure Compiler phase.

Following up on this, by locally publishing mdoc with https://github.com/scalameta/mdoc/blob/6a5be8cbde534662b27f1b68d2e12384a31216c9/mdoc-js/src/main/scala/mdoc/modifiers/JsModifier.scala#L80 adjusted I was able to do fullOptJS but disable GCC. Well, turns out that it is the GCC phase.