Values porting log

Here, I try to record my steps for porting the Values package from VisualWorks to Squeak.

In your VisualWorks 8.3 image

• have {Smalltalk Transform Project} (1.4.0.3,chaider) loaded
• have [Squeak Fileout PDFtalk] (3.0.0.2,chaider) loaded, with empty transformations:

ValuesTransform
	^PackageChange new

File out from VW with

Squeak fileOutValues

. Start squeak, open the Transcript and file in “Values.Squeak.st” with

FileStream fileIn: 'C:\Users\Christian\Documents\image\Values.Squeak.st'

it loads 1 / 4 of the file before a syntax error occurs:

localSpecification
	<constant: #name class: #"Invalid literal character ->"{Printvalue}>
	<constant: #value class: #{Printvalue}>

The Transcript shows:

UndefinedObject»DoIt (PackageManifest is Undeclared) Attempt to create ManifestValues as a subclass of nil. Possibly a class is being loaded before its superclass.

VisualWorks has a special syntax for specifying a class in a namespace as literal; e.g. #{PDFtalk.Name}.

Fixed by adding add a transformation for the class method #localSpecification in any Value subclass. This translates #{Integer} to #(#Integer) and #{PDFtalk.Name} to #(#PDFtalk #Name).

ValuesTransform
	^PackageChange hierarchyChanges: (Array with: (ClassChange
		classReference: #{Smalltalk.Value}
		classChanges: (Array with: (Rewrite method: #localSpecification rule: #replaceLiteralBindingWithPath))))

Published as [Squeak Fileout PDFtalk] (3.0.0.3,chaider).

The Transcript warning complains that the class ManifestValues cannot be created as subclass of PackageManifest which is unknown.

Changed ChunkStream»#writeProperties:in:parents: to

• use Object as superclass instead of PackageManifest
• renamed class to About<Package>

Published as {Smalltalk Transform Project} (1.4.0.4,chaider).

FileOut from VW, then fileIn into a fresh Squeak image.

Loads about 80% until it hits the error that ColorValue is not defined.

The Transcript shows:

Class>>nameRelativeTo: (Root is Undeclared) 
Class>>isInScope: (NameScope is Undeclared) 
UndefinedObject>>DoIt (ColorValue is Undeclared) 
UndefinedObject>>fromBytesRed:green:blue: (ColorValue is Undeclared) 
UndefinedObject>>fromBytesRed:green:blue: (ColorValue is Undeclared) 
UndefinedObject>>DoIt (ColorValue is Undeclared) 
UndefinedObject>>DoIt (ColorValue is Undeclared) 
UndefinedObject>>DoIt (ColorValue is Undeclared) 
UndefinedObject>>DoIt (ColorValue is Undeclared) 
UndefinedObject>>DoIt (ColorValue is Undeclared)

The system class ColorValue of VW is roughly equivalent to Color in Squeak. But instead of renaming all ColorValue references to Color, I define ColorValue as subclass of Color. With this, the target system is not polluted with compatibility methods for ColorValue.

This is expressed in the transformation with #newSuperclasses. The new transform looks like:

ValuesTransform
	^PackageChange
		newSuperclasses: (Valuemap with: #{Smalltalk.ColorValue} -> #Color)
		hierarchyChanges: (Array with: (ClassChange
			classReference: #{Smalltalk.Value}
			classChanges: (Array with: (Rewrite method: #localSpecification rule: #replaceLiteralBindingWithPath))))

The Transcript shows undeclared class references in two methods of class class.

Class>>nameRelativeTo: (Root is Undeclared) 
Class>>isInScope: (NameScope is Undeclared)

To handle this, we add local changes to the transformation. Local changes refer to classes in the source system.

ValuesTransform
	^PackageChange
		newSuperclasses: (Valuemap with: #{Smalltalk.ColorValue} -> #Color)
		hierarchyChanges: (Array with: (ClassChange
			classReference: #{Smalltalk.Value}
			classChanges: (Array with: (Rewrite method: #localSpecification rule: #replaceLiteralBindingWithPath))))
		localChanges: self valuesLocalTransform
 
valuesLocalTransform
	^Array with: (ClassChange
		classReference: #{Class}
		instanceChanges: (Array
			with: (Replace method: #nameRelativeTo: code: #_sq_nameRelativeTo:)
			with: (Replace method: #isInScope: code: #_sq_isInScope:)))

These transformations replace the body of the existing methods of class Class with the body of the #code methods.

Published as {Smalltalk Transform Project} (1.4.0.5,chaider) with minor changes (updated comments and corrected spelling).

Published as [Squeak Fileout PDFtalk] (3.0.0.4,chaider) with the updated transformations.

FileOut from VW, then fileIn into a fresh Squeak image.

Loads about 85% until it hits the error that GeneralBindingReference is not defined.

The Transcript shows:

UndefinedObject>>DoIt (GeneralBindingReference is Undeclared) 
UndefinedObject>>DoIt (GeneralBindingReference is Undeclared) 
UndefinedObject>>DoIt (GeneralBindingReference is Undeclared) 
UndefinedObject>>DoIt (GeneralBindingReference is Undeclared) 

Since GeneralBindingReference is specific to namespaces in VW, we don't need to port the class extension methods. For this we add the class to the #unusedClasses in our #ValuesTransform PackageChange:

ValuesTransform
	^PackageChange
		unusedClasses: #(#{Smalltalk.GeneralBindingReference})
		newSuperclasses: (Valuemap with: #{Smalltalk.ColorValue} -> #Color)
		hierarchyChanges: (Array with: (ClassChange
			classReference: #{Smalltalk.Value}
			classChanges: (Array with: (Rewrite method: #localSpecification rule: #replaceLiteralBindingWithPath))))
		localChanges: self valuesLocalTransform

Published as [Squeak Fileout PDFtalk] (3.0.0.5,chaider) with the updated transformation.

FileOut from VW, then fileIn into a fresh Squeak image.

Loads about 97% until it hits the error that Timestamp is not defined.

The Transcript shows:

UndefinedObject>>DoIt (Timestamp is Undeclared) 
UndefinedObject>>DoIt (Timestamp is Undeclared) 
UndefinedObject>>DoIt (Timestamp is Undeclared) 
UndefinedObject>>DoIt (Timestamp is Undeclared) 
UndefinedObject>>DoIt (Timestamp is Undeclared) 

We do the same trick as in FileIn x and set DateAndTime as superclass of Timestamp. The new Transformation is:

ValuesTransform
	^PackageChange
		unusedClasses: #(#{Smalltalk.GeneralBindingReference})
		newSuperclasses: (Valuemap
			with: #{Smalltalk.ColorValue} -> #Color
			with: #{Timestamp} -> #DateAndTime)
		hierarchyChanges: (Array with: (ClassChange
			classReference: #{Smalltalk.Value}
			classChanges: (Array with: (Rewrite method: #localSpecification rule: #replaceLiteralBindingWithPath))))
		localChanges: self valuesLocalTransform

Published as [Squeak Fileout PDFtalk] (3.0.0.6,chaider) with the updated transformation.

FileOut from VW, then fileIn into a fresh Squeak image.

Loads without errors or warnings!.

First milestome achieved: fileIn without errors.

Next step: fileIn the tests.

Added Squeak class methods #fileOutValuesTesting with the transformation:

ValuesTestingTransform
	^PackageChange hierarchyChanges: (Array with: (ClassChange
		classReference: #{Smalltalk.Value}
		classChanges: (Array with: (Rewrite method: #localSpecification rule: #replaceLiteralBindingWithPath))))

FileOut from VW with:

Squeak fileOutValuesTesting

, then fileIn into a Squeak image with Values loaded.

Loads without errors.

The Transcript shows:

ValuemapTests>>testIndexedAccess (SubscriptOutOfBoundsError is Undeclared) 
ValuemapTests>>testIndexedAccess (SubscriptOutOfBoundsError is Undeclared) 
ValuemapTests>>testIndexedAccess (NonIntegerIndexError is Undeclared) 
ValuemapTests>>testIndexedAccess (NonIntegerIndexError is Undeclared) 
ValuemapTests>>testKeyedAccess (NotFoundError is Undeclared) 
ValuemapTests>>testRemoving (NotFoundError is Undeclared) 
ValuemapTests>>testRemoving (NotFoundError is Undeclared) 
ValuemapTests>>testRemoving (NotFoundError is Undeclared) 
ValuemapTests>>testRemoving (NotFoundError is Undeclared)