sqlalchemy / sqlalchemy/mako

Allow control statements (if, else, endif, etc.) to be closed so they can be inlined

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feature lexer low priority
Dominant language
Python
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Description

Migrated issue, originally created by Anonymous

In line with the discussion here:

http://groups.google.com/group/mako-discuss/browse_thread/thread/835ab6db0bb0cdb4

The pertinent parts quoted:

However, if the case is that Jinja2's (% if <expr> %}, because it has a 
closing %} allows it to be inlined like {% if <expr> %} <html> {% else %} 
<html> {% endif %}, then I'd want to think a bit bigger here.   I'd want to 
go into match_control_line() as we did and just find some way to make the 
newline optional:

% if <expr>:\n
    <html>\n
% else:\n
   <html>\n
% endif\n

we could perhaps just co-opt the { } verbosity:

{% if <expr>:}  <html> {% else:} <html> {% endif}

or just rip them off totally:

{% if <expr> %}  <html> {% else %} <html> {% endif %}

either of the above would require a rewritten (either in-place or additional 
version of) match_control_line(), as we'd be doing the same kind of matching 
which we do in match_expression(), which is that we need to make use of 
parse_until_text() so that we properly skip over anything that might be 
Python code.     I'd want the two formats to be completely interchangeable:

% if expr:
<html> {% else %} <html> 
% endif

{% if <expr> %} <html>
% elif <expr>:
<html>
% else:
<html> {% endif %}

just some ideas but I'd need someone to be motivated to help patch out 
lexer.py and add new tests as well.

I've frequently used Python's native 1 if 1 else 0 syntax, but it doesn't always seem ideal.

This is the only thing I can think of that other template languages can do that I wish Mako had.

Thank you for making Mako.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in lexer.py, especially match_control_line() and the parsing around parse_until_text(), as identified in the issue. Review the existing control-line tests, then define tests for interchangeable multiline and inline if/else/elif/endif forms; done means inline control statements parse and render correctly without breaking the existing syntax.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
web-dev
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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