Do not append missing XML declaration in formatted responses

[this-is-r-gaurav]

Fixes #1156.

[BoboTiG]

I would do all the work into the else: block, see my next comment.

[this-is-r-gaurav]

Yeah it would be more appropriate, i missed that part.

[BoboTiG]

Perhaps something less invasive could be used? An idea:

        try: ...
        else:
            has_declaration = body.startswith('<?xml version')
            body = pretty_xml(parsed_body,
                              encoding=parsed_body.encoding,
                              indent=self.format_options['xml']['indent'],
                              standalone=parsed_body.standalone)
            if not has_declaration:
                body = body[body.index('\n') + 1:]

         return body

[this-is-r-gaurav]

Yes seems more intuitive. I was not aware about the ordering of prolog attributes matter. so i choose to find out what is the first tag in original xml document.
But i tried one test case:
If unformatted file is this

<?xml version="1.0"?>
<root><test>testValue</test></root>

what would be expected, this

<?xml version="1.0"?>
<root>
  <test>testValue</test>
</root>

or

<?xml version="1.0" encoding="utf-8"?>
<root>
  <test>testValue</test>
</root>

[BoboTiG]

xmlminidom will set the encoding. I think it is good as-is.

[BoboTiG]

Sorry for the previous answer. I did a mistake.
HTTPie should not alter the response content.

[this-is-r-gaurav]

Oh okay, sorry been busy with personal work will try to fix that as well.

[this-is-r-gaurav]

@BoboTiG addressed the above test case as well.
But assuming if test case file is:

<root><test>testValue</test></root>

Output will be

<?xml version="1.0" ?>
<root>
  <test>testValue</test>
</root>

[BoboTiG]

Given that input, the output should be:

<root>
  <test>testValue</test>
</root>

[BoboTiG]

Could you add tests for different cases also 🙏 ?

[this-is-r-gaurav]

Sure I will add them.

[this-is-r-gaurav]

Not Adding test case

<root><test>testValue</test></root>

because it can be addressed by simple_raw.xml

[this-is-r-gaurav]

https://github.com/httpie/httpie/issues?q=is%3Aissue+is%3Aopen+label%3A%22help+wanted%22+ @BoboTiG Any other issues i could take a look at?

[BoboTiG]

Let's see with @jakubroztocil.

[isidentical]

@this-is-r-gaurav thanks for the PR, but we decided to with another way (#1227).