[0.54 - iOS] fetch HEAD requests fail with `Invalid response for blob`

Performing a HEAD request with fetch causes an Invalid response for blob error on iOS

Environment

Environment: OS: macOS Sierra 10.12.6 Node: 8.6.0 Yarn: Not Found npm: 5.3.0 Watchman: 4.9.0 Xcode: Xcode 9.1 Build version 9B55 Android Studio: 3.0 AI-171.4443003

Packages: (wanted => installed) react: 16.3.0-alpha.1 => 16.3.0-alpha.1 react-native: 0.54.0 => 0.54.0

Expected Behavior

The request should complete without error.

Actual Behavior

The RCTNetworking native module in iOS does not construct an empty blob for HEAD responses like Android does. Instead it returns an empty string as the response. However, whatwg-fetch always sets the responseType to blob for the XMLHttpRequest so the empty string is invalid.

Relevant lines of code: https://github.com/github/fetch/blob/fcc4e1b48cfb5a2b1625fcd6eac06d954b00ccb6/fetch.js#L454 https://github.com/facebook/react-native/blob/6eef7de46ee5c5004854c1cdd5cd83f2a608f622/Libraries/Network/XMLHttpRequest.js#L253-L258

Invalid response for blob: 
handleException @ index.bundle?platform=ios&dev=true&minify=false:13132
handleError @ index.bundle?platform=ios&dev=true&minify=false:12174
reportFatalError @ index.bundle?platform=ios&dev=true&minify=false:783
__guardSafe @ index.bundle?platform=ios&dev=true&minify=false:2360
callFunctionReturnFlushedQueue @ index.bundle?platform=ios&dev=true&minify=false:2165
t @ RNDebuggerWorker.js:1

Steps to Reproduce

1 Clone and run https://github.com/lingokids/FetchError

(I tested on an iPhone 7)

[olivierlesnicki]

+1

[janicduplessis]

cc @grabbou f5207ba9c764f33ef83fa897f6014d67193be0e2 might be worth cherry-picking into 0.54 and 0.55