Bug #841
TemplateParser triggers TemplateKeyError if an "if" clause refers to a non-existing key, and no way to check if key exists before triggering if clause.
Description
TemplateParser triggers a TemplateKeyError if an {{ if [var] }} clause is triggered when "var" is not defined. There is also no way currently to check if a variable is defined in a template and trigger a conditional block based on if the variable has been defined.
Associated revisions
Revision 248:52b0751e2acf
(diff)
Introduced {{ ifpresent }} construct to TemplateParser. This checks for presence of the provided tags and their indices. Multiple tags can be provided per check, as well as {{ elif }} and {{ else }} clauses, where {{ elif }} supports additional tags. This resolves #841.
History
#1 Updated by Elmer de Looff almost 12 years ago
- Status changed from New to Resolved
- % Done changed from 0 to 70
Applied in changeset 52b0751e2acf.
#2 Updated by Elmer de Looff almost 12 years ago
- Category set to TemplateParser
- Assignee changed from Elmer de Looff to Niek Bergman
- Target version set to µWeb alpha release
Niek,
The TemplateKeyError you encountered should've been a TemplateNameError, which has been changed in r246. The {{ if }} construct does not and will not support referencing nonexistent template variables, because this would inevitably lead to disastrous surprises.
However, I've added a construct that does exactly what you want to do here, and that is checking the presence of a tag, or even its index:
<html>
<body>
{{ ifpresent [one] [two]}}
<p>key number <b>one</b> AND <b>two</b> are provided</p>
{{ elif [three] }}
<p>one of keys <b>one</b> and <b>two</b> (or both) are missing, though <b>three</b> is provided</p>
{{ else }}
<p>none of the keys are provided</p>
{{ endif }}
</body>
</html>
Please verify these changes work for you.
#3 Updated by Niek Bergman almost 12 years ago
Confirmed to work.
#4 Updated by Elmer de Looff almost 12 years ago
- Status changed from Resolved to Closed
- % Done changed from 70 to 100
Corrected wrong error class raised. Tags that are not found should always raise TemplateNameError, not TemplateKeyError. This is related to issue #841.