Shell.add, file will be closed by shell.Shell automatically

[treasersimplifies]

I found in request.go:

func (r *Request) Send(c *http.Client) (*Response, error) {
    // snip
    if resp.StatusCode >= http.StatusBadRequest {
        // snip
        io.Copy(ioutil.Discard, resp.Body)
        resp.Body.Close()
    }
}

when developer use go-ipfs-api, they typically:

// var shells []*shell.Shell = ... connection to a lot of ipfs nodes..
localFile, err := os.Open(localfPath)
defer localFile.Close()
if err != nil {
    return nil, err
}
err = retry.Retry(func(attempt uint) error {
    response, err = shells[attempt].Add(localFile)
    if err != nil {
	return err
    }
    return nil
},
    strategy.Limit(limit),
)

So when fail on one shell.add, shell will close the file it pass, it's not good. The close of file should leave to developer.

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[Stebalien]

That code closes the response body, not the request file.

However, go-ipfs-files closes the request file when it finishes reading it. This could be changed, but it would be a fair amount of work for little gain (we rely on this logic to close files as we traverse directory trees).

In general, the code above will never work as you'd need to seek back to the beginning of the file for each retry. The current behavior (an error) is significantly better than the bug you'd get if we didn't close the file (empty files).

[aschmahmann]

@treasersimplifies is this issue a request for adding better documentation to the Add command and/or go-ipfs-files? Mutating file handles as you work with them seems pretty common place, but it may be worth pointing out that it's happening.

PRs welcome if you have wording/documentation suggestions here.