net/http: GET request with http.NoBody fails on js/wasm

[tarndt]

What version of Go are you using (go version)?

$ go version
go version go1.13.4 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

GOARCH=wasm GOOS=js running on Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:71.0) Gecko/20100101 Firefox/71.0

What did you do?

I executed code that makes a HTTP GET request using net/http facilities and it failed with the following error:

Fail:  Get https://localhost:8443/v1/endpoint: net/http: fetch() failed: <object>

I then added js.Global().Get("console").Call("log", args[0]) on line 160 of roundtrip_js.go and observed:

TypeError: "HEAD or GET Request cannot have a body."
    valueCall https://localhost:8443/wasm_exec.js:327
    run https://localhost:8443/wasm_exec.js:475
    <anonymous> https://localhost:8443/:9

I then changed the body of the request created from http.NoBody to nil and observed a successful request being made:

• Fails: req, err := http.NewRequest(http.MethodGet, URL, http.NoBody)
• Succeeds: req, err := http.NewRequest(http.MethodGet, URL, nil)

P.S. In roundtrip_js.go and the similar stdlib JavaScript platform code, if existing error reporting code such as:

err := fmt.Errorf("net/http: fetch() failed: %s", args[0].String())

is replaced with:

err := fmt.Errorf("net/http: fetch() failed: %s", js.Error{args[0]})

the output changes from:

net/http: fetch() failed: <object>

To

net/http: fetch() failed: JavaScript error: HEAD or GET Request cannot have a body.

which is substantially more helpful and perhaps warrants another issue. 😸

What did you expect to see?

Success. I expect nil and http.NoBody to function identically with respect to client `*http.Request``'s.

What did you see instead?

Failure, GET requests under GOARCH=wasm GOOS=js fail when the request body is http.NoBody rather than nil.