On Wed, Feb 6, 2019 at 5:15 AM Robert Engels <reng...@ix.netcom.com> wrote:
>
> I see now, but if that can be the case, shouldn’t the Body be documented that
> the Reader may be a ReaderWithLen, and the consumer is free to type
> check/cast? If not, you are using internal details that you should not be.
Yes, the documentation should say if the reader has a Len() method it
would be used to set the ContentLength. Len is no longer an internal
detail then.
>
> This is a problem with Go in general. Because the returned object
> “implements” some interface because it happens to have the required method,
> doesn’t mean it was designed to be used that way, or that it has the required
> semantics - unless documented to have them.
I agree with you there. Len() is straight forward, but in general just
because a function is named something doesn't mean it'll do the same
thing for all implementations. On the other end of the spectrum is
Java-like interfaces where you want explicit inheritance of a specific
interface. I don't know if there's anything in between, but I like
Go's approach much better.
>
> On Feb 6, 2019, at 2:22 AM, Matteo Biagetti <matteo.biage...@gmail.com> wrote:
>
> Make sense, thanks for explanation
>
>
>
> Il giorno mercoledì 6 febbraio 2019 07:28:54 UTC+1, Burak Serdar ha scritto:
>>
>> On Tue, Feb 5, 2019 at 8:13 PM robert engels <ren...@ix.netcom.com> wrote:
>> >
>> > That’s what I was trying to point out. Your design is not correct. The
>> > Body is a Reader, not a Buffer - the length of the request/body may be
>> > indeterminate - that is, a stream. Attempting to get the length of an
>> > underlying buffer is not only probably not possible, but not correct in
>> > many situations.
>>
>> The length of the body *may* be indeterminate, and if that's the case,
>> the underlying Reader will not have a Len method. The design is to
>> handle the case where the underlying Reader is a Buffer with a Len
>> method. If the Reader has Len, then the NopCloser derived from that
>> will also have a Len, and NewRequest can set the content length. If
>> the Reader does not have Len, then the content length is unknown.
>>
>> >
>> > There is a reason the Body is a ReaderCloser and not a buffer. It is part
>> > of the http specification.
>> >
>> > On Feb 5, 2019, at 9:00 PM, Burak Serdar <bse...@ieee.org> wrote:
>> >
>> > On Tue, Feb 5, 2019 at 7:00 PM Robert Engels <ren...@ix.netcom.com> wrote:
>> >
>> >
>> > Shouldn’t you just be taking the content length from the header if
>> > forwarding the same body. There is no need for the length of the body.
>> >
>> >
>> > True. What I was suggesting is a fix for the general case.
>> >
>> >
>> > On Feb 5, 2019, at 6:53 PM, Burak Serdar <bse...@ieee.org> wrote:
>> >
>> > On Tue, Feb 5, 2019 at 5:18 PM Dan Kortschak <d...@kortschak.io> wrote:
>> >
>> > Personally, I think this is a bug in the behaviour of NewRequest. See h
>> > ttps://github.com/golang/go/issues/18117 for some additional context.
>> >
>> >
>> > Agreed. One solution could be to have:
>> >
>> > type HasLen interface {
>> > int Len()
>> > }
>> >
>> > Then have NopCloser return a nopCloser with len if the underlying
>> > implementation has len, with the obvious changes to NewRequest.Ugly,
>> > but can be done without API changes.
>> >
>> >
>> >
>> >
>> > On Tue, 2019-02-05 at 05:18 -0800, matteo....@gmail.com wrote:
>> > I've the following situation:
>> > I proxy a request to another server and when I made a POST and create
>> > a new
>> > request, the contentLength is zero:
>> >
>> > req2, _ := http.NewRequest(req.Method, newApiUrl , req.Body)
>> > fmt.Println("New request from body:", req2.ContentLength) //
>> > print 0
>> >
>> > Checking in the source code of the NewRequest func Body don't respect
>> > some
>> > interface and populate the ContentLength field.
>> >
>> > Could be a bug? Which could be a valid approach in order to create a
>> > new
>> > request from an existing one and correct set the Body length?
>> >
>> > A working example here:
>> >
>> > https://play.golang.org/p/SvCDLj0NrXb
>> >
>> > Thanks!
>> >
>> >
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