Empty block in middle of %if...%elif...%elif...%else...%endif doesn't get a pass in the Python, leading to an IndentationError

Migrated issue, originally created by Anonymous

How-To-Reproduce:

% if True:
test
% elif lose:
## do nothing
% elif False:
broken
% endif

Results:

An IndentationError pointing at the next line of code after the do-nothing block, complaining that Python was expecting an indented block.

Workaround:
Add <%pass%> to the do-nothing block

Attachments: 146.patch | 146.2.patch | 146.3.patch

Michael Bayer (@zzzeek) wrote:

a very old bug which I thought we had a bug report for, thought we fixed, but all these assumptions (except the first) are wrong.

Anonymous wrote:

Don't you have to add a 'pass' in that same situation in Python? Isn't this asking mako behavior to diverge from Python unnecessarily? Although it would indeed be more convenient to not have to manually insert the pass statement.

Michael Bayer (@zzzeek) wrote:

the patch is in 1b4d1fb but doesn't actually fix the above test case, it appears that the comment line screws it up:

from mako.template import Template
template = r"""
% if True:
test
% elif lose:
##  do nothing
% elif False:
broken
% endif
"""

t = Template(template)
print t.render()



Traceback (most recent call last):
  File "test.py", line 12, in <module>
    t = Template(template)
  File "/Users/classic/dev/mako/mako/template.py", line 258, in __init__
    (code, module) = _compile_text(self, text, filename)
  File "/Users/classic/dev/mako/mako/template.py", line 606, in _compile_text
    code = compile(source, cid, 'exec')
  File "memory:0x1004a68d0", line 29
    elif False:
       ^
IndentationError: expected an indented block

taking out the comment, it's fine:

from mako.template import Template
template = r"""
% if True:
test
% elif lose:
% elif False:
broken
% endif
"""

t = Template(template)
print t.render()

Michael Bayer (@zzzeek) wrote:

great, 8cce610 and we're done ! thanks!

Changes by Michael Bayer (@zzzeek):

changed status to closed

Hi there, it seems that if the empty statement is the first one it still fails:

from mako.template import Template
template = r"""
% if True:
% elif lose:
test
% elif False:
broken
% endif
"""

t = Template(template)
print(t.render())  # IndentationError: expected an indented block

So the bug is not entirely fixed.

hi there -

unfortunately Mako needs a maintainer to be able to look into these issues, I can only submit PRs with tests I don't have time to diagnose intricate issues like these.

no worries I found a workaround, but could you please just reopen the ticket so that when a maintainer is active, he will know what to fix ? Thanks!

Sure! github lets you do all that stuff too.

Fixes: sqlalchemy#146

Fix the unexpected error that occurs when an empty control block is u…

@cocolato

The remaining case reported here — where the first control block in the chain is empty (or contains only a comment) — was fixed in commit 7a19fbe via #387 (thanks @cocolato), released in Mako 1.3.3.

The code generator now inserts a pass for four situations, including "the first control block with no content other than comments." Regression tests (test_blank_control_9/10/11, test_commented_blank_control_9/10 in ControlTest) cover these variants.

Verified on current main that all reported variants — middle-empty, middle-empty-with-comment, first-empty, first-empty-with-comment, and all-empty — now compile and render correctly. Closing.

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Empty block in middle of %if...%elif...%elif...%else...%endif doesn't get a pass in the Python, leading to an IndentationError #146

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Empty block in middle of %if...%elif...%elif...%else...%endif doesn't get a pass in the Python, leading to an IndentationError #146

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sqlalchemy-bot commented on Aug 10, 2010

sqlalchemy-bot commented on Jun 25, 2011

sqlalchemy-bot commented on Apr 3, 2012

sqlalchemy-bot commented on Apr 6, 2012

sqlalchemy-bot commented on Apr 6, 2012

smarie commented on Apr 12, 2019

zzzeek commented on Apr 12, 2019

smarie commented on Apr 12, 2019

zzzeek commented on Apr 12, 2019

zzzeek commented on Aug 4, 2026

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