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How To Transpile A Relay Query From TypeScript To ES5?

- 1 answer

I'm writing a web app in TypeScript. The app uses React and Relay from Facebook. My TypeScript source code gets compiled into ES6 code using the TypeScript compiler TSC. Then, the ES6 code gets transpiled into ES5 code using Babel. In order for Relay to work in the browser, a Babel plugin needs to transform the Relay GraphQL queries: https://facebook.github.io/relay/docs/guides-babel-plugin.html. The problem is, because TSC first transpiles these queries, the Babel Relay plugin doesn't recognize them anymore so they don't get transpiled into something the browser understands, so the browser throws an error:

Uncaught Invariant Violation: RelayQL: Unexpected invocation at runtime. Either the Babel transform was not set up, or it failed to identify this call site. Make sure it is being used verbatim as Relay.QL.

My TypeScript source code:

const SiteQuery = {
    store: () => Relay.QL`query { site }`
};

... this gets compiled by TSC into something like this:

var SiteQuery = {\r\n    store: function () { return (_a = [\"query { site }\"], _a.raw = [\"query { site }\"], Relay.QL(_a)); var _a; }\r\n};

... instead of something like this (because the Babel Relay plugin doesn't do its work properly):

var SiteQuery = {\n    store: function store() {\n        return (function () {\n            return {\n                fieldName: 'site',\n                kind: 'Query',\n                metadata: {},\n                name: 'Router',\n                type: 'Site'\n            };

This is because the Babel Relay plugin doesn't recognize the transpiled version, and as a result it doesn't transpile the query into something the browser understands.

How to make this work?

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Answer

You need to tell the Typescript compiler to transpile to ES6, then use Babel with babel-relay-plugin and es2015 preset to transpile the code to ES5 to run in your browser.

I recommend using Webpack to orchestrate all this. These will get you started:

  1. http://www.jbrantly.com/typescript-and-webpack/
  2. http://www.jbrantly.com/es6-modules-with-typescript-and-webpack/

The posts were written for Babel 5.x, so you'll need to manually add es2015 preset to make sure Babel compiles the ES6 sources to ES6.

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source: stackoverflow.com
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