Removed unnecessary NewLine from Textarea From Widget

[edelbluth]

When building a form with Django and using a Textarea Widget, the value rendering is always prepended by a NewLine (\r\n).
This makes the textarea never empty when it is, and changes the value for the following submissions.

This commit fixes this behaviour with just a trivial change.

Explanation:

When there is no (or an empty) value defined for the textarea, it shall be rendered as

<textarea></textarea>

and not as

<textarea>
</textarea>

At least in XHTML5 documents, this is a major difference.

Let's see what happens with a value:

This\nis\na\nvalue

This is currently rendered as this:

<textarea>
This
is
a
value</textarea>

Which renders in the browser to:

+-------------------------------------------+
|                                           |  <- empty line!
| This                                      |
| is                                        |
| a                                         |
| value                                     |
+-------------------------------------------+

After applying my patch, the rendering changes to this:

<textarea>This
is
a
value</textarea>

Which (correctly) renders in the browser to:

+-------------------------------------------+
| This                                      |
| is                                        |
| a                                         |
| value                                     |
+-------------------------------------------+

As a workaround to get around with the current implementation, I've overridden the render method of the original Widget class:

from django import forms
from django.forms.utils import flatatt
from django.utils.encoding import force_text
from django.utils.html import format_html

class FixedTextarea(forms.Textarea):

    def render(self, name, value, attrs=None):
        if value is None:
            value = ''
        final_attrs = self.build_attrs(attrs, name=name)
        return format_html('<textarea{}>{}</textarea>',
                           flatatt(final_attrs),
                           force_text(value))

[aaugustin]

This essentially reverts 78f6669 which will reintroduce Trac 8627.

I don't know why the test introduced in that commit doesn't catch the regression, though.

[timgraham]

Please see https://code.djangoproject.com/ticket/24871 for discussion of the issue.