[Zope-dev] Re: SVN: Zope/branches/ajung-zpt-end-game/lib/python/Products/PageTemplates/tests/testExpressions.py Fix a test that was testing wrong behaviour: primitive types
Tres Seaver wrote: If a subexpression returns a callable, you're telling me that you think the top-level expression is supposed to call it? That's nuts! The spec[1] says: When a TALES path expression is evaluated, it attempts to traverse each path, from left to right, until it succeeds or runs out of paths. To traverse a path, it first fetches the object stored in the variable. For each path segment, it traverses from the current object to the subobject named by the path segment. Once a path has been successfully traversed, the resulting object is the value of the expression. If it is a callable object, such as a method or class, it is called. The semantics of traversal (and what it means to be callable) are implementation-dependent. If a traversal step fails, evaluation immediately proceeds to the next path. If there are no further paths, an error results. Calling the callable happens *before* attempting alternate expressions, not after. That is partly because the *call* might be what triggers the alternation. [1] http://www.zope.org/Wikis/DevSite/Projects/ZPT/TALES%20Specification%201.3 You're absolutely right. I filed a collector issue for Zope 3: http://www.zope.org/Collectors/Zope3-dev/638 This will be fixed soon in Zope 3. Philipp ___ Zope-Dev maillist - Zope-Dev@zope.org http://mail.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope )
[Zope-dev] Re: SVN: Zope/branches/ajung-zpt-end-game/lib/python/Products/PageTemplates/tests/testExpressions.py Fix a test that was testing wrong behaviour: primitive types
Tres Seaver wrote:
Philipp von Weitershausen wrote:
Log message for revision 68244:
Fix a test that was testing wrong behaviour: primitive types
werent' called if they were the result of a path expression, while
all other callables were called. This tests now tests the correct
behaviour (which happens to be already implemented by the Zope 3
TALES engine)
+assert ec.evaluate('x | python:int') == 0
Wait a minute -- that isn't a path expression there!
Yes it is. This line could explicitly written as:
assert ec.evaluate('path: x | python:int') == 0
The python: expression is just part of the path expression.
The '|' is not supposed to change the rules for evaluation of the
subexpressions!
It doesn't change the rules for the evaluation of the subexpressions
themselves. But it might easily change the rules of what happens to the
result of the expression afterwards.
If
'int' or the like were somehow avaialbe at module scope, or via
'options' or another top-level name, then they should be called *when
they are the last item in a path expression*.
The test was actually correct beofore: because tne PathExpression, 'x',
raises, the PythonExpression, 'int', is evalutated. The result of a
subexpression is not suppoeed to be called,
No, not the result of a subexpression, but the result of the overall
path expression. That's how it works in both Zope 2 and Zope 3. Zope 2
just special-cases primitive types.
Philipp
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[Zope-dev] Re: SVN: Zope/branches/ajung-zpt-end-game/lib/python/Products/PageTemplates/tests/testExpressions.py Fix a test that was testing wrong behaviour: primitive types
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Hash: SHA1
Philipp von Weitershausen wrote:
Tres Seaver wrote:
Philipp von Weitershausen wrote:
Log message for revision 68244:
Fix a test that was testing wrong behaviour: primitive types
werent' called if they were the result of a path expression, while
all other callables were called. This tests now tests the correct
behaviour (which happens to be already implemented by the Zope 3
TALES engine)
+assert ec.evaluate('x | python:int') == 0
Wait a minute -- that isn't a path expression there!
Yes it is. This line could explicitly written as:
assert ec.evaluate('path: x | python:int') == 0
The python: expression is just part of the path expression.
The '|' is not supposed to change the rules for evaluation of the
subexpressions!
It doesn't change the rules for the evaluation of the subexpressions
themselves. But it might easily change the rules of what happens to the
result of the expression afterwards.
If
'int' or the like were somehow avaialbe at module scope, or via
'options' or another top-level name, then they should be called *when
they are the last item in a path expression*.
The test was actually correct beofore: because tne PathExpression, 'x',
raises, the PythonExpression, 'int', is evalutated. The result of a
subexpression is not suppoeed to be called,
No, not the result of a subexpression, but the result of the overall
path expression. That's how it works in both Zope 2 and Zope 3. Zope 2
just special-cases primitive types.
If a subexpression returns a callable, you're telling me that you think
the top-level expression is supposed to call it? That's nuts! The
spec[1] says:
When a TALES path expression is evaluated, it attempts to traverse
each path, from left to right, until it succeeds or runs out of
paths. To traverse a path, it first fetches the object stored in the
variable. For each path segment, it traverses from the current object
to the subobject named by the path segment.
Once a path has been successfully traversed, the resulting object is
the value of the expression. If it is a callable object, such as a
method or class, it is called. The semantics of traversal (and what it
means to be callable) are implementation-dependent.
If a traversal step fails, evaluation immediately proceeds to the
next path. If there are no further paths, an error results.
Calling the callable happens *before* attempting alternate expressions,
not after. That is partly because the *call* might be what triggers
the alternation.
[1]
http://www.zope.org/Wikis/DevSite/Projects/ZPT/TALES%20Specification%201.3
Tres.
- --
===
Tres Seaver +1 202-558-7113 [EMAIL PROTECTED]
Palladion Software Excellence by Designhttp://palladion.com
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--
===
Tres Seaver +1 202-558-7113 [EMAIL PROTECTED]
Palladion Software Excellence by Designhttp://palladion.com
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** No cross posts or HTML encoding! **
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