Fwd: [squeak-dev] Strange behavior of ContextVariableInspector

> That was issue 987 from the bugtracker, which you closed earlier  
> today after integrating the fix made as per Eliot's pointers. ;)
>
> Cheers,
> Henry
> On Oct 17, 2009, at 7:30 18PM, Stéphane Ducasse wrote:
>
>>
>>
>> Begin forwarded message:
>>
>>> From: Eliot Miranda <[hidden email]>
>>> Date: October 16, 2009 12:10:14 AM GMT+02:00
>>> To: The general-purpose Squeak developers list <[hidden email]
>>> >
>>> Subject: Re: [squeak-dev] Strange behavior of  
>>> ContextVariableInspector
>>> Reply-To: The general-purpose Squeak developers list <[hidden email]
>>> >
>>>
>>>
>>>
>>> On Thu, Oct 15, 2009 at 1:02 PM, Igor Stasenko  
>>> <[hidden email]> wrote:
>>> I suspect this is due to latest updates to debugger & compiler etc,
>>> brought by Eliot.
>>>
>>> To display a context variable 'contents', a message #contents is  
>>> sent
>>> to ContextVariableInspector.
>>> The problem is, that in TextMorphForEditView>>newContents:
>>> which sends this message to model (which is a
>>> ContextVariableInspector) expects that returned value is text, or
>>> string at least.
>>> While at some point, this is not always true, and inspection of
>>> different context slots in debugger could lead to interesting  
>>> results,
>>> where
>>> #contents returns an actual object, which does not implements  
>>> #asText
>>> , and as result i often get an
>>> DNU: SmallInteger>>asText
>>> or similar.
>>>
>>> The root of evil, i think, is in
>>> ContextVariableInspector>>toggleIndex: method, in following code:
>>>
>>> self contentsIsString
>>>        ifTrue: [contents := self selection]
>>>        ifFalse: [contents := self selectionPrintString]].
>>>
>>> which sometimes returns an actual object (self selection) instead of
>>> (self selectionPrintString).
>>>
>>> I don't really understand, what exactly tests the  
>>> #contentsIsString method:
>>>
>>> contentsIsString
>>>        "Hacked so contents empty when deselected"
>>>
>>>        ^ #(0 2 3) includes: selectionIndex
>>>
>>> This defines which indices in the context inspector answer meta-
>>> values rather than actual slot contents.  Open up a debugger on  
>>> the activation of a method with args and/or temps and you'll see
>>> thisContext
>>> stack top
>>> all temp vars
>>> textOrStream
>>> aContext
>>> receiver
>>> aRequestor
>>> failBlock
>>> logFlag
>>> methodNode
>>> method
>>> value
>>> toLog
>>> itsSelection
>>> itsSelectionString
>>> thisContext is an object, but "stack top" and "all temp vars" are  
>>> strings computed by ContextvariablesInspector>>selection. i.e.
>>>
>>> selection
>>> "Refer to the comment in Inspector|selection."
>>> selectionIndex = 0 ifTrue:[^''].
>>> selectionIndex = 1 ifTrue: [^object].
>>> selectionIndex = 2 ifTrue: [^object stackPtr > 0 ifTrue: [object  
>>> top]].
>>> selectionIndex = 3 ifTrue: [^object tempsAndValues].
>>> ^object debuggerMap namedTempAt: selectionIndex - 3 in: object
>>>
>>> So the meta values at index 0 (unselected null string), 2 & 3  
>>> shouldn't be sent printString, otherwise e.g. an unselected CVI  
>>> would show '' (the printString of ByteString new) instead of  
>>> nothing.
>>>
>>>
>>> maybe a proper fix would be to test additionally, that selection is
>>> string, and if not, then return false, so
>>> caller will use #selectionPrintString later.
>>>
>>> The right thing is to ensure thatContextvariablesInspector  
>>> contentsIsString fieldList replaceSelectionValue: & selection all  
>>> agree.  I think I added "stack top" to the list.  I may have  
>>> forgotten to integrate the changes for one or more of these which  
>>> in my image are (also attached):
>>>
>>>  !ContextVariablesInspector methodsFor: 'accessing' stamp: 'eem  
>>> 5/21/2008 12:31'!
>>> fieldList
>>> "Refer to the comment in Inspector|fieldList."
>>>
>>> object == nil ifTrue: [^Array with: 'thisContext'].
>>> ^fieldList ifNil:[fieldList := (Array with: 'thisContext' with:  
>>> 'stack top' with: 'all temp vars') , object tempNames]! !
>>>
>>> !ContextVariablesInspector methodsFor: 'selecting' stamp: 'eem  
>>> 3/6/2009 10:05'!
>>> contentsIsString
>>> ^ #(0 3) includes: selectionIndex! !
>>>
>>> !ContextVariablesInspector methodsFor: 'selecting' stamp: 'eem  
>>> 7/18/2008 11:18'!
>>> replaceSelectionValue: anObject
>>> "Refer to the comment in Inspector|replaceSelectionValue:."
>>>
>>> ^selectionIndex = 1
>>> ifTrue: [object]
>>> ifFalse: [object namedTempAt: selectionIndex - 3 put: anObject]! !
>>>
>>> !ContextVariablesInspector methodsFor: 'selecting' stamp: 'eem  
>>> 6/10/2008 09:37'!
>>> selection
>>> "Refer to the comment in Inspector|selection."
>>> selectionIndex = 0 ifTrue:[^''].
>>> selectionIndex = 1 ifTrue: [^object].
>>> selectionIndex = 2 ifTrue: [^object stackPtr > 0 ifTrue: [object  
>>> top]].
>>> selectionIndex = 3 ifTrue: [^object tempsAndValues].
>>> ^object debuggerMap namedTempAt: selectionIndex - 3 in: object! !
>>>
>>> --
>>> Best regards,
>>> Igor Stasenko AKA sig.
>>>
>>>
>> <ContextVariablesInspector.st>
>>>
>>
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