Reflection in Pharo5
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This document summarizes a talk about reflection and abstract syntax trees (AST) in Pharo5. It discusses how the AST is now more integrated and accessible via methods like #ast. Annotations called MetaLinks can be added to AST nodes to modify behavior. A reflective compiler called Basis uses AST annotations and metaobjects to implement features like live recompilation without restarting the image. Questions from the audience are then invited.
![DEMO
(OrderedCollection>>#do:) ast.
[ 1 + 2 ] sourceNode == thisContext method ast blockNodes first
• ASTCache: as twice, get the same answer
(flushed on image save for now)](https://image.slidesharecdn.com/a7ygditjqukfxfxpfnnk-signature-f3467f098552cb2446a746c4cbd16bbe9766381f936e73d00fd4660aff5b8d20-poli-150715081135-lva1-app6891/85/Reflection-in-Pharo5-11-320.jpg)
![Link: metaobject
The object to send
a message to
link := MetaLink new
metaObject: [self halt]](https://image.slidesharecdn.com/a7ygditjqukfxfxpfnnk-signature-f3467f098552cb2446a746c4cbd16bbe9766381f936e73d00fd4660aff5b8d20-poli-150715081135-lva1-app6891/85/Reflection-in-Pharo5-31-320.jpg)
![Link: condition
boolean or block
link := MetaLink new
…..
condition: [self someCheck]](https://image.slidesharecdn.com/a7ygditjqukfxfxpfnnk-signature-f3467f098552cb2446a746c4cbd16bbe9766381f936e73d00fd4660aff5b8d20-poli-150715081135-lva1-app6891/85/Reflection-in-Pharo5-36-320.jpg)
![Reifications: condition
link := MetaLink new
condition: [: object | object == 1];](https://image.slidesharecdn.com/a7ygditjqukfxfxpfnnk-signature-f3467f098552cb2446a746c4cbd16bbe9766381f936e73d00fd4660aff5b8d20-poli-150715081135-lva1-app6891/85/Reflection-in-Pharo5-40-320.jpg)
![Statement Coverage
link := MetaLink new
metaObject: #node;
selector: #tagExecuted.
“set this link on all the AST nodes"
(ReflectivityExamples>>#exampleMethod) ast
nodesDo: [:node | node link: link].](https://image.slidesharecdn.com/a7ygditjqukfxfxpfnnk-signature-f3467f098552cb2446a746c4cbd16bbe9766381f936e73d00fd4660aff5b8d20-poli-150715081135-lva1-app6891/85/Reflection-in-Pharo5-42-320.jpg)
Reflection in Pharo5
- 1. Reflection in Pharo5 ESUG 2015 Marcus Denker http://www.pharo.org
- 2. Everything is an Object
- 3. Everything?
- 5. Methods, yes
- 6. But Code?
- 7. Code is a String!
- 8. AST: Abstract Syntax Tree
- 9. AST in Pharo5 • AST of the Refactoring browser • Transformation • Visitors • Annotations (properties) • Deeper integrated: • Pretty Printing, Syntax Highlight, Suggestions • Compiler uses RB AST
- 10. AST in Pharo5 • Easy access • #ast • Demo: method and block
- 11. DEMO (OrderedCollection>>#do:) ast. [ 1 + 2 ] sourceNode == thisContext method ast blockNodes first • ASTCache: as twice, get the same answer (flushed on image save for now)
- 12. AST + Tools
- 13. Opal Compiler • Uses RB AST • Based on Visitors Text AST AST +vars IR CM Parser Semantic Analysis AST Translator+ IRBuilder BytecodeBuilder+ Encoder
- 14. Opal: API • All staged are Pluggable • e.g Semantic Analyzer or Code Generator can be changed. • compiler options
- 15. Opal: Bytecode editing • IR can be used to manipulate methods on a bytecode level Text AST AST +vars IR CM Parser Semantic Analysis AST Translator+ IRBuilder BytecodeBuilder+ Encoder
- 16. Too complicated
- 17. Too low level
- 18. Can we do better?
- 19. AST Meta Annotation • We have an AST with properties • We have Opal with Pluggable API
- 20. Can’t we use that?
- 21. Basis: the Evil Twin CompiledMethod ReflectiveMethod Know each other Bytecode AST
- 22. Basis: the Evil Twin ReflectiveMethod AST run: aSelector with: anArray in: aReceiver self installCompiledMethod. self recompileAST. self installCompiledMethod. ^compiledMethod valueWithReceiver: aReceiver arguments: anArray
- 23. Demo: Morph • Morph methods do: #createTwin • Morph methods do: #invalidate • inspect “Morph methods”
- 24. Putting it together • Annotate the AST • Create Twin if needed • Invalidate method • Next call: generate code changed by annotation
- 25. recompileAST ast compilationContext semanticAnalyzerClass: RFSemanticAnalyzer; astTranslatorClass: RFASTTranslator. ast doSemanticAnalysis. "force semantic analysis" compiledMethod := ast generate: compiledMethod trailer. compiledMethod reflectiveMethod: self.
- 26. Annotations?
- 27. MetaLink
- 28. DEMO: Simple Link node := (ReflectivityExamples>>#exampleMethod) ast. link := MetaLink new metaObject: (Object new); selector: #halt. node link: link. ReflectivityExamples new exampleMethod
- 29. Meta Link • When setting link: • create twin if needed • install reflective method • On execution • generate code and execute, install CM
- 31. Link: metaobject The object to send a message to link := MetaLink new metaObject: [self halt]
- 32. Link: selector The selector to send link := MetaLink new ….. selector: #value
- 33. Link: control before, after, instead link := MetaLink new ….. control: #after
- 34. Link: control after: #ensure: wrap link := MetaLink new ….. control: #after
- 35. Link: control instead: last link wins (for now no AOP around) link := MetaLink new ….. control: #instead
- 36. Link: condition boolean or block link := MetaLink new ….. condition: [self someCheck]
- 37. Link: arguments what to pass to the meta?
- 38. Reifications • Every operation has data that it works on • Send: #arguments, #receiver, #selector • Assignment: #newValue, #name • All: #node, #object, #context
- 39. Link: arguments what to pass to the meta? link := MetaLink new ….. arguments: #(name newValue)
- 40. Reifications: condition link := MetaLink new condition: [: object | object == 1];
- 41. Virtual meta • Reifications can be the meta object link := MetaLink new metaObject: #receiver; selector: #perform:withArguments:; arguments: #(selector arguments).
- 42. Statement Coverage link := MetaLink new metaObject: #node; selector: #tagExecuted. “set this link on all the AST nodes" (ReflectivityExamples>>#exampleMethod) ast nodesDo: [:node | node link: link].
- 43. Variables • Helper methods • But: can’t we annotate variables directly? Point assignmentNodes
- 45. RoadMap • Pharo4: Opal is default • Pharo5 • Remove old Compiler/AST • Reflectivity: First finished version • Pharo6: Object specific links
- 46. Users • Tools of ObjectProfile are being ported • BreakPoints Pharo5 • Coverage Kernel by Pavel • ….
- 47. Thanks! • Work of many people… • Too many to list here. (And I would forget for sure someone)
- 48. Questions ?