Error loading DevTools

I have just updated from Expo 37.0.0 to 38.0.0 and have updated the Expo CLI to go with it (now at latest 3.21.12).

The app seems to be running OK (still some digging to do regarding breaking changes and API changes), but i immediately get Error loading DevTools in my localhost when i launch the app in iOS sim.

I also get the following in my console;

DevTools failed to load SourceMap: Could not load content for http://localhost:19003/debugger-ui/debuggerWorker.[xx].js.map: HTTP error: status code 500, net::ERR_HTTP_RESPONSE_CODE_FAILURE

This repeats multiple times in the console.

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I still have this issue and no where to turn for advice… i thought it could be a teething issue, but i seem to be up to date and still having problems

Experienced this too with Expo@38.0.0 and expo-cli@3.22.3 after upgrading from Expo@37.

It was magically fixed after deleting node_modules, yarn.lock, package-lock.json, and then doing
yarn install (instead of my usual npm install).

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I am running this error too, and I am using npm instead of yarn.

Looking in the networking error stack I noticed: following error

{
   "type": "error",
   "id": "1",
   "payload": { 
      "message": "Cannot use GraphQLSchema \"[object GraphQLSchema]\" from another module or realm.\n\nEnsure that there is only one instance of \"graphql\" in the node_modules\ndirectory. If different versions of \"graphql\" are the dependencies of other\nrelied on modules, use \"resolutions\" to ensure only one version is installed.\n\nhttps://yarnpkg.com/en/docs/selective-version-resolutions\n\nDuplicate \"graphql\" modules cannot be used at the same time since different\nversions may have different capabilities and behavior. The data from one\nversion used in the function from another could produce confusing and\nspurious results."
  }
}

or

Cannot use GraphQLSchema “[object GraphQLSchema]” from another module or realm.

Ensure that there is only one instance of “graphql” in the node_modules
directory. If different versions of “graphql” are the dependencies of other
relied on modules, use “resolutions” to ensure only one version is installed.

https://yarnpkg.com/en/docs/selective-version-resolutions

Duplicate “graphql” modules cannot be used at the same time since different
versions may have different capabilities and behavior. The data from one
version used in the function from another could produce confusing and
spurious results.

I looked in the package-lock.json and noticed that react-native references eslint-plugin-relay for some reason and it comes with new graphql version.

There is following PR open to update the graphql version in the developer tools: https://github.com/expo/expo-cli/pull/2286 which should fix this issue.

Note: I suspect that it works with yarn because yarn handles this conflicting dependencies slighty different.

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