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Adjusts bundler output to work with Node. #20

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May 21, 2024
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Adjusts bundler output to work with Node. #20

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Adjusts bundler output to work with Node.
gunsch May 21, 2024
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gunsch May 21, 2024
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14 changes: 12 additions & 2 deletions src/bundler/compiler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -21,10 +21,20 @@ export function compile(env: tsvfs.VirtualTypeScriptEnvironment): string {
const src =
env.languageService.getEmitOutput(appEntrypointFilename).outputFiles[0]
?.text ?? ''
// Adapt bundle CommonJS output to format expected by runtime-lite.
// Adapt bundle CommonJS output to format expected by our runtimes.
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thanks for this beefy comment and PR message. I didn't understand why var specifically was needed--it's hoisted outside the block but why? some issue with @devvit/public-api? I know the code is cryptic by nature but I see it and immediately think it's safe to rewrite `"use strict"; module.exports ??= {}; const {exports} = module; }\n'. anything you can do to make this clearer would be appreciated.

the other thing I was thinking is that changing app code is hard but changing runtime-lite or the compute @devvit/public-api bundle is possible if wanted.

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When we load a cjs file into a module in node, the contents are basically wrapped like this:

(function(exports, require, module, __filename, __dirname) {
// Module code actually lives in here
});

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beefiness++

added more comment, hopefully that explains better

we could change runtime-lite and drop this src.replace call entirely, though that's a little outside the scope I wanted to dig into. we can't fix this on the compute side though without some ugly Node hackery (i.e. monkey-patching the contents of require('module').wrapper)

// This is a light hack that satisfies two different runtime needs:
// 1. runtime-lite needs `exports` to be defined and aliased to `module.exports` like so.
// 2. Node wraps the bundle's code in this function:
//
// (function(exports, require, module, __filename, __dirname) {
// // [ bundle code here ]
// });
//
// We can't overwrite `module.exports` (the resulting bundle won't actually export what
// it needs to), and we can't declare `exports` with const/let ("already been declared").
return src.replace(
/^"use strict";/,
'"use strict"; module.exports = {}; const {exports} = module;'
'"use strict"; if (!module.exports) { module.exports = {}; var exports = module.exports; }\n'
)
}

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