Well, it looks like I was wrong.
I just tested the following in Flash, and then both give the same results (i.e.
return the attribute):
var emp = e.employee.(@id == 1).@name; // name of employee with id 1
var foo = e.employee.(1 == @id).@name; // name of employee with id 1
> On Aug 7, 2018, at 10:27 AM, Harbs <harbs.li...@gmail.com> wrote:
>
> Your example does not seem to be right to me.
>
> Here’s the overview of how filters are supposed to work from the spec:
>
>> Overview
>> When the left operand evaluates to an XML object, the filtering predicate
>> adds the left operand to the front of the scope chain of the current
>> execution context, evaluates the Expression with the augmented scope chain,
>> converts the result to a Boolean value, then restores the scope chain. If
>> the result is true, the filtering predicate returns an XMLList containing
>> the left operand. Otherwise it returns an empty XMLList.
>> When the left operand is an XMLList, the filtering predicate is applied to
>> each XML object in the XMLList in order using the XML object as the left
>> operand and the Expression as the right operand. It concatenates the results
>> and returns them as a single XMLList containing all the XML properties for
>> which the result was true. For example,
>>
>> var john = e.employee.(name == "John"); // employees with name John
>> var twoemployees = e.employee.(@id == 0 || @id == 1); // employees with id's
>> 0 & 1
>> var emp = e.employee.(@id == 1).name; // name of employee with id 1
>>
>> The effect of the filtering predicate is similar to SQL’s WHERE clause or
>> XPath’s filtering predicates.
>> For example, the statement:
>>
>> // get the two employees with ids 0 and 1 using a predicate
>> var twoEmployees = e..employee.(@id == 0 || @id == 1);
>>
>> produces the same result as the following set of statements:
>> // get the two employees with the ids 0 and 1 using a for loop
>> var i = 0;
>> var twoEmployees = new XMLList();
>> for each (var p in e..employee) {
>> with (p) {
>> if (@id == 0 || @id == 1) {
>> twoEmployees[i++] = p;
>> }
>> }
>> }
>
> The question is what is "the front of the scope chain of the current
> execution context”? I’m pretty sure that means the start of sub-expressions.
> I don’t see how that can apply to the right-hand of comparison expressions.
> There is nothing in the spec about figuring out if a part of an expression is
> referring to XML or XMLList.
>
>> On Aug 7, 2018, at 9:45 AM, Alex Harui <aha...@adobe.com.INVALID> wrote:
>>
>> I don't get what portion of the spec has to do with whether we append "node"
>> to various expressions. IMO, the changes I made only affect 6b. 6a is
>> handled by generating a function with "node" as the parameter (because node
>> is list[i] in the spec). The task in 6b is to correctly evaluate any e4x
>> filter expression. I'm not sure what the limits are on what you can have in
>> a filter expression, but if you can have just plain "@app" anywhere in the
>> filter expression, I don't believe scoping rules would know to apply that to
>> the "node" parameter without generating the "node" before "@app".
>>
>> There is a chance that the Flex Compiler was using "magic" to generate the
>> "node" and really should have reported an error. I do remember being told
>> that the filter function can be "anything". Even:
>> (var foo:int = @app.length(); foo > @bar.length())
>>
>> If there are actual rules in the spec about evaluating the expression, that
>> might apply to how we handle these expressions, otherwise I think the right
>> thing is to resolve each expression and if the expression does not resolve
>> to anything else, assume that it applies to the node. I know the logic in
>> EmitterUtils.writeE4xFilterNode isn't covering all cases. It is trying to
>> see what the expression resolves to, and returns false for known conditions
>> (like a member of a class). Just make it return false for your case (and
>> feel free to add that case to the tests). Eventually we'll have enough
>> cases to either call it "good enough" or figure out a better way to
>> determine when the expression applies to "node".
>>
>> My 2 cents,
>> -Alex
>>
>> On 8/6/18, 11:20 PM, "Harbs" <harbs.li...@gmail.com> wrote:
>>
>> I just looked at the spec. I think it’s correct to append “node” to the
>> first statement of the expression only. The only exception seems to be
>> expressions which use boolean expressions (i.e. || or &&) in which case each
>> piece of the boolean expression should be considered a self-contained
>> expression. So in your example, there are really two filter expressions:
>> 1. hasOwnProperty("@app”)
>> 2. @app.length() > 0
>>
>> Both of those should have node appended to the front, but nothing else.
>>
>> Here’s the relevant semantics in the spec (the important bit being 6a):
>>
>>> 6. For i = 0 to list.[[Length]]-1
>>> a. Add list[i] to the front of the scope chain
>>> b. Let ref be the result of evaluating Expression using the augmented scope
>>> chain of step 6a
>>> c. Let match = ToBoolean(GetValue(ref))
>>> d. Remove list[i] from the front of the scope chain
>>> e. If (match == true), call the [[Append]] method of r with argument list[i]
>>> 7. Return r
>>
>> Makes sense?
>>
>> Harbs
>>
>>> On Aug 7, 2018, at 1:39 AM, Alex Harui <aha...@adobe.com.INVALID> wrote:
>>>
>>> In porting Tour De Flex, there were patterns like this (explorerTree is
>>> XML):
>>>
>>> explorerTree..node.(hasOwnProperty("@app") && @app.length() > 0)
>>>
>>> The compiler logic before I made any changes yesterday just assumed that
>>> the first expression was a reference to the node parameter but other
>>> expressions were not, but it looks like the expression "@app.length()" was
>>> allowed in Flex as a reference to the node. So I think the compiler has to
>>> determine what expressions evaluate to "nothing" which implies they are
>>> references to the node, and what did resolve to something. This is all new
>>> logic and I don't know how to determine all of the test cases up front, so
>>> we'll have to keep tuning it as we find patterns that don't work as we want
>>> them to.
>>>
>>> In your case, if the expression resolves to a VariableDefinition, that
>>> probably means that isn't a reference to node. Not exactly sure, so you
>>> should debug into it to see what the node pattern is and return false.
>>>
>>> Thanks,
>>> -Alex
>>>
>>> On 8/6/18, 3:28 PM, "Harbs" <harbs.li...@gmail.com> wrote:
>>>
>>> Doesn’t it always need to be a method for it to reference the node?
>>>
>>> I.e. child() should be node.child(), but foo.baz would not.
>>>
>>>> On Aug 7, 2018, at 1:12 AM, Alex Harui <aha...@adobe.com.INVALID> wrote:
>>>>
>>>> Yep, we need more intelligent understanding of when a reference is to the
>>>> node or not.
>>>>
>>>> Debug into EmitterUtils.writeE4xFilterNode and figure out the node pattern
>>>> you need.
>>>>
>>>> -Alex
>>>>
>>>> On 8/6/18, 3:09 PM, "Harbs" <harbs.li...@gmail.com> wrote:
>>>>
>>>> var folderFolders:XMLList =
>>>> assetXML.folder.(child('key').indexOf(folder.key) == 0);
>>>> var folderImages:XMLList =
>>>> assetXML.image.(child('key').indexOf(folder.key) == 0);
>>>>
>>>> Is now compiled as:
>>>>
>>>> var /** @type {XMLList} */ folderFolders =
>>>> this.assetXML.child('folder').filter(function(node){return
>>>> (node.child('key').indexOf(node.folder.key) == 0)});
>>>> var /** @type {XMLList} */ folderImages =
>>>> this.assetXML.child('image').filter(function(node){return
>>>> (node.child('key').indexOf(node.folder.key) == 0)});
>>>>
>>>> “node.folder.key” is not correct. “folder” is a local variable of an un
>>>> related object type.
>>>>
>>>> I assume this broke with the recent XML filter changes.
>>>>
>>>> Harbs
>>>>
>>>
>>>
>>>
>>
>>
>>
>
