Don't inconsistently add XML declarations

[isidentical]

Resolves #1156

[jkbrzt]

I think we should also include a test that verifies the behavior we’re correcting (i.e., that an unwanted XML declaration is indeed added by the library).

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I just noticed that the parser also collapses empty tags:

$ echo '<a></a>' | http --offline pie.dev/post content-type:application/xml

<?xml version="1.0" encoding="utf-8"?>
<a/>

And I assume that might not be the last unwanted alteration. Not sure if we should spend too much time trying to fix this.

(I was against reintroducing the XML formatter but was assured that this one has none the issues of the original one, but it seems like we’re in a similar situation.)

[isidentical]

I think we should also include a test that verifies the behaviour we’re correcting (i.e., that an unwanted XML declaration is indeed added by the library).

We already have such tests (we had tests that did not have a declaration in their raw version, but have it on their formatted. So I simply fixed them).

And I assume that might not be the last unwanted alteration. Not sure if we should spend too much time trying to fix this.

It is due to Python's parser is not really caring about roundtripability. I've looked around on PyPI, but I have not yet found an XML parser that claims to have a full-roundtripability feature. If that is what we are looking at, we could drop this or explicitly mention about the formatters are only support for semantical equivalence.

[codecov-commenter]

Codecov Report

Merging #1227 (775716f) into master (4d7d6b6) will decrease coverage by 0.56%.
The diff coverage is 94.91%.

❗ Current head 775716f differs from pull request most recent head f2c0ca7. Consider uploading reports for the commit f2c0ca7 to get more accurate results

@@            Coverage Diff             @@
##           master    #1227      +/-   ##
==========================================
- Coverage   97.28%   96.72%   -0.57%     
==========================================
  Files          67       81      +14     
  Lines        4235     5398    +1163     
==========================================
+ Hits         4120     5221    +1101     
- Misses        115      177      +62     

Impacted Files	Coverage Δ
tests/test_binary.py	100.00% <ø> (ø)
httpie/compat.py	31.11% <27.90%> (-68.89%)	⬇️
tests/conftest.py	77.14% <58.33%> (-9.82%)	⬇️
tests/test_ssl.py	91.01% <66.66%> (-3.93%)	⬇️
httpie/manager/__main__.py	82.35% <82.35%> (ø)
httpie/models.py	94.73% <83.33%> (-2.64%)	⬇️
httpie/output/formatters/colors.py	92.66% <88.88%> (-0.92%)	⬇️
httpie/manager/core.py	92.85% <92.85%> (ø)
httpie/manager/plugins.py	93.39% <93.39%> (ø)
httpie/cli/json_form.py	93.87% <93.87%> (ø)
... and 52 more

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[jkbrzt]

I think we should also include a test that verifies the behavior we’re correcting (i.e., that an unwanted XML declaration is indeed added by the library).

We already have such tests (we had tests that did not have a declaration in their raw version, but have it on their formatted. So I simply fixed them).

What I mean is that we implicitly rely on the library auto-adding the declaration. For example, we assume there’ll always be lines[0].

Let’s add an explicit test case verifying this assumption still holds (something like assert pretty('<x/>') == '<?xml …?><x/>').

explicitly mention about the formatters are only support for semantical equivalence.

Let’s do that.

[isidentical]

What I mean is that we implicitly rely on the library auto-adding the declaration. For example, we assume there’ll always be lines[0].

I see. I've changed it now to ensure there is at least one line and the first line is some sort of a declaration. If that is the case, we either get rid of it or replace it with the original version (if there are any).

Let’s do that.

Sure!