Teach template_parser.py about jinja2 whitespace markers.

[rishig]

Being able to use http://jinja.pocoo.org/docs/2.10/templates/#whitespace-control feature would greatly increase the readibility of our template files. Currently tools/lib/template_parser.py doesn't seem to know about this feature.

To get the error, you can edit a file like templates/zerver/emails/password_reset.source, and replace a {% trans %}, {% endtrans %} pair with {% trans -%}, {%- endtrans %}. Then run tools/lint templates/zerver/emails/password_reset.source.

[zulipbot]

Hello @zulip/server-tooling members, this issue was labeled with the "area: tooling" label, so you may want to check it out!

[amanpro30]

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[timabbott]

@adnrs96 this is probably an issue for you given your background with the template parser.

[kskonanur]

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[ayushah]

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[ayushah]

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[refeed]

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[andersk]

Reopening because this fix was incomplete. Jinja2 allows you to strip independently from either side of a variable, block, or comment.

$ echo '{%- set x = 1 %}' > test.html
$ tools/pretty-print-html test.html
Prettifying: test.html
Traceback (most recent call last):
  File "/srv/zulip/tools/lib/template_parser.py", line 163, in tokenize
    s = get_jinja2_whitespace_stripped_tag(text, state.i)
  File "/srv/zulip/tools/lib/template_parser.py", line 373, in get_jinja2_whitespace_stripped_tag
    raise TokenizationException('Tag missing "-%}"', text[i:end+2])
lib.template_parser.TokenizationException: ('Tag missing "-%}"', '{%- set x = 1 %}')

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "tools/pretty-print-html", line 21, in <module>
    clean_html(filenames)
  File "tools/pretty-print-html", line 12, in clean_html
    phtml = pretty_print_html(html)
  File "/srv/zulip/tools/lib/pretty_print.py", line 15, in pretty_print_html
    tokens = tokenize(html)
  File "/srv/zulip/tools/lib/template_parser.py", line 172, in tokenize
    e.line_content))
lib.template_parser.TemplateParserException: Tag missing "-%}" at Line 1 Col 1:"{%- set x = 1 %}"

[timabbott]

@vrongmeal do you want to take the project of fixing the remaining issue here?