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Make the react-native entry point Jest compatible #6012

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merged 1 commit into from
Jul 31, 2023
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Make the react-native entry point Jest compatible #6012

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2 changes: 1 addition & 1 deletion CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
* None

### Fixed
* <How to hit and notice issue? what was the impact?> ([#????](https://github.com/realm/realm-js/issues/????), since v?.?.?)
* Fix Jest issues when testing against Realm ([#6003](https://github.com/realm/realm-js/issues/6003))
* None

### Compatibility
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30 changes: 0 additions & 30 deletions packages/realm-react/custom-resolver.cjs
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3 changes: 1 addition & 2 deletions packages/realm-react/jest.config.json
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
{
"verbose": true,
"preset": "react-native",
"resolver": "./custom-resolver.cjs",
"roots": [
"<rootDir>/src"
],
Expand All @@ -13,4 +12,4 @@
},
"testRegex": "(/__tests__/.*.(test|spec)).(jsx?|tsx?|js?|ts?)$",
"testTimeout": 30000
}
}
17 changes: 16 additions & 1 deletion packages/realm/index.react-native.js
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Expand Up @@ -19,4 +19,19 @@
/* eslint-disable @typescript-eslint/no-var-requires -- We're exporting using CJS assignment */
/* eslint-env commonjs */

module.exports = require("./dist/bundle.react-native").Realm;
// eslint-disable-next-line no-undef -- In React Native, process is not defined, but in Jest it is
const isJest = process?.env?.JEST_WORKER_ID !== undefined;
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I'm a bit sad that we need to do this 😞 It would be better if we could find a way to keep this pure from runtime checks of the environment ... historically we've been bitten by the brittleness of these many times before.

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Also - I'm surprised you're not getting an Uncaught ReferenceError: process is not defined when running on React Native 🤔

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@takameyer takameyer Jul 31, 2023 •
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We can't get around the react-native preset for jest, which is basically ensuring the react-native entry point is being loaded. I did a lot of digging around this and this was the best solution I could find. At least it's very dependent on Jest and has very little impact on the experience.

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@takameyer takameyer Jul 31, 2023 •
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'm surprised you're not getting an Uncaught ReferenceError: process is not defined when running on React Native 🤔

I need to refine the comment. process is actually defined in react-native, but for some reason it is not typed.

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@kraenhansen kraenhansen Jul 31, 2023 •
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which is basically ensuring the react-native entry point is being loaded

As per that link, it looks to me that we could probably export the Node.js bundle via the require condition (since it's giving priority to require over react-native and the opposite is true for the defaults of the metro bundler) and avoid the runtime check?

https://github.com/facebook/react-native/blob/1ba7bc0eb1099b64601e0037f3ef717fcd1302e3/packages/react-native/jest/react-native-env.js#L15C9-L15C9

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@takameyer takameyer Jul 31, 2023 •
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How do we set the require condition for our users?
The linked code is ran by adding preset: "react-native" to the jest config, which is automatically done when initializing a React Native project. Jest isn't looking for this automatically in imported packages, as far as I can tell.
Jest also doesn't allow for multiple presets

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@kraenhansen kraenhansen Jul 31, 2023 •
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Add this line

      "require": "./index.node.js",

after

realm-js/packages/realm/package.json

Line 31 in 0b9dd8b

"node": "./index.node.js",

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Oh boy...that works!


let entryPoint;

if (isJest) {
// Define a require function that will load the node bundle
// otherwise, metro will preemptively load the node bundle
const nodeRequire = require;
// Jest is running, use the node bundle
entryPoint = nodeRequire("./dist/bundle.node");
} else {
entryPoint = require("./dist/bundle.react-native");
}

module.exports = entryPoint.Realm;
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I'd suggest simply inlining this assignment. No need to store it in entryPoint.

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Good idea. I was doing a lot of dancing around how metro bundled this, to ensure it didn't pre-load the node entry point. Setting require to a variable was the solution.

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