Node.js - realFetch.call is not a function

[kevzettler]

Trying to use this in a node.js worker and seeing error realFetch.call is not a function

(node:41803) UnhandledPromiseRejectionWarning: TypeError: realFetch.call is not a function
    at ../node_modules/isomorphic-fetch/fetch-npm-node.js.module.exports (/Users/kevzettler/code/hypeworks/build/webpack:/node_modules/isomorphic-fetch/fetch-npm-node.js:8:1)
    at AssetStore.<anonymous> (/Users/kevzettler/code/hypeworks/build/webpack:/AssetStore.ts:47:30)
    at step (/Users/kevzettler/code/hypeworks/build/0.server.worker.js:36403:23)
    at Object.next (/Users/kevzettler/code/hypeworks/build/0.server.worker.js:36384:53)
    at /Users/kevzettler/code/hypeworks/build/0.server.worker.js:36378:71
    at new Promise (<anonymous>)
    at ./AssetStore.ts.__awaiter (/Users/kevzettler/code/hypeworks/build/0.server.worker.js:36374:12)
    at AssetStore../AssetStore.ts.AssetStore.fetchBinary (/Users/kevzettler/code/hypeworks/build/0.server.worker.js:36443:16)
    at executeAction (/Users/kevzettler/code/hypeworks/build/webpack:/node_modules/mobx/lib/mobx.module.js:928:1)
    at AssetStore.fetchBinary (/Users/kevzettler/code/hypeworks/build/webpack:/node_modules/mobx/lib/mobx.module.js:915:1)

[jgcmarins]

facing the same problem

[jgcmarins]

tested on version 2.2.1 and version 3.0.0 and I can confirm it is not happening on version 2.2.1, only on version 3.0.0

[hsiaosiyuan0]

I think it's a bug from node-fetch because it tagged itself as module see here so webpack load its .mjs instead of .js despite their exports have different semantics(scroll former two links to bottom to see the differences)

I guess you may in a isomorphic case, if so try to indicate webpack that node-fetch should be treated as it's commonjs module via webpack.config.js:

module.exports = {
  // ...
  externals: {
    'node-fetch': 'commonjs2 node-fetch',
  }
};

[airhorns]

I ended up switching to cross-fetch which seems to work in the same way without the same issue!

[aseure]

Same issue here. We've switched to cross-fetch as well which solves the issue for us.

FYI we've made it work with isomorphic-fetch with the following configuration but we thought it was too brittle to keep:

module.exports = {
  // ...
  resolve: {
    // ...
    mainFields: ['main', 'module']
  } 
}

With our target setting set to node the default for mainFields was ['module', 'main'].

We've also tried to made it per-dependency for both node-fetch and/or isomorphic-fetch by doing the following but this one did not work:

module.exports = {
  // ...
  resolve: {
    // ...
    byDependency: {
      'node-fetch': {
        mainFields: ['main', 'module']
      },
      'isomorphic-fetch': {
        mainFields: ['main', 'module']
      }
    }
  } 
}