Principled Syntactic Code Completion with Placeholders
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Principled Syntactic Code Completion using Placeholders SLE’16 - Amsterdam Sebastian Erdweg, Guido Wachsmuth, Eelco Visser Eduardo Souza
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Transcript of Principled Syntactic Code Completion with Placeholders
Principled Syntactic Code Completion using Placeholders
SLE’16 - Amsterdam
Sebastian Erdweg, Guido Wachsmuth, Eelco VisserEduardo Souza
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*S. Amann, S. Proksch, S. Nadi, and M. Mezini. A study of visual studio usage in practice. In SANER, 2016.
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Syntactic Completion
Semantic Completion
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Syntactic Completion
Semantic Completion
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Problems
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Problems
Unsound!
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Soundness: the resulting program should have no additional syntax errors.
Problems
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Problems
Unsound!
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Incomplete
!
Completeness: any program should be derivable through code completion.
Problems
Unsound!
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Problems
Incomplete
!Unso
und!
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Ad-hoc!
Problems
Incomplete
!Unso
und!
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Language Specification
Syntax Definition
Name Binding
Type Constraints
Code Completion
Syntactic Completion
Semantic Completion
Textual/Projectional IDE
Language Workbenches
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Unsound!
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Sound and Complete Syntactic Code Completion from Language
Specifications
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Language Specification
SyntaxDefinition
Name Binding
Type Constraints
Code Completion
SyntacticCompletion
Semantic Completion
Textual IDE
Sound!
Complete!
Language Workbenches
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Language Specification
SDF3 Name Binding
Type Constraints
Code Completion
SyntacticCompletion
Semantic Completion
Textual IDE
Sound!
Complete!
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Explicit Placeholders
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Incompleteprograms
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Make incompleteness valid using placeholders!
Incompleteprograms
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Deriving Syntactic Completion from the Syntax Definition
context-free syntax
Statement ::= "if" "(" Exp ")" Statement "else" Statement {"If"}
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context-free syntax // placeholder rule
Statement ::= “$Statement" {“Statement-Plhdr"}
context-free syntax //regular production rule
Statement ::= "if" "(" Exp ")" Statement "else" Statement {"If"}
Make placeholders part of the language
Stm-Plhdr
If
Exp-Plhdr Stm-Plhdr
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Stm-Plhdr
context-free syntax //regular production rule
Statement ::= "if" "(" Exp ")" Statement "else" Statement {"If"}
signature constructors // AST signatures
If : Exp * Statement * Statement -> Statement
Calculate placeholder expansions
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rules rewrite-placeholder: Statement-Plhdr() -> If(Exp-Plhdr(), Statement-Plhdr(), Statement-Plhdr())
Format Expansions
context-free syntax
Statement ::= "if" "(" Exp ")" Statement "else" Statement {cons("If")}
context-free syntax // placeholder rule
Statement ::= "$Statement"Parse Placeholders
Expand Placeholders
Incompleteprograms
Completeprograms
Expand placeholder
Expand/overwrite placeholders
Correctprograms
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Completeprograms
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How to expand?
Completeprograms
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Type a placeholder?
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Type a placeholder?
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Type a placeholder?
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Inferring Placeholders
Optional Parent
List of Statements
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Add Element to List
Add Optional Element
Placeholder Inference
Optional Parent
List of Statements
Add Optional Element
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No source region
Add first or last element
Placeholder Inference
Add Element to List
ClassDecl
class “A” {NoParent ConsMethod
[…]
}NilField
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Placeholder Inference - Optional
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ClassDecl
class “A” {NoParent ConsMethod
[…]
}NilField
Placeholder Inference - Optional
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ClassDecl
class “A” {NoParent ConsMethod
[…]
}NilField
Placeholder Inference - Optional
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Placeholder Inference - Optional
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Placeholder Inference - Lists
[…]
[…]
Method
Cons
VarDecl
AssignInt “x”
VarRef
“x”
Add
Int
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Cons
Nil
{ return[…]
int ;
Int
=
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Placeholder Inference - Lists
[…]
[…]
Method
Cons
VarDecl
AssignInt “x”
VarRef
“x”
Add
Int
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Cons
Nil
{ return[…]
int ;
Int
=
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Placeholder Inference - Lists
[…]
[…]
Method
Cons
VarDecl
AssignInt “x”
VarRef
“x”
Add
Int
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Cons
Nil
{ return[…]
int ;
Int
=
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Placeholder Inference - Lists
[…]
[…]
Method
Cons
VarDecl
AssignInt “x”
VarRef
“x”
Add
Int
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Cons
Nil
{ return[…]
int ;
Int
=
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Incompleteprograms
Completeprograms
Expand placeholder
Infer placeholder
Correctprograms
Infer placeholder
Expand/overwrite placeholders
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Incorrectprograms
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Error Recovery
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context-free syntax //regular syntax rules
Statement.VarDecl = <<Type> <ID>;> Statement.Assign = <<VarRef> = <Exp>;>
Insertion Rules
// derived insertion rules for placeholderscontext-free syntax
Type.Type-Plhdr = {symbol-insertion} ID.ID-Plhdr = {symbol-insertion} Statement.Statement-Plhdr = {symbol-insertion} VarRef.VarRef-Plhdr = {symbol-insertion} Exp.Exp-Plhdr = {symbol-insertion}
// derived insertion rules for literalslexical syntax
"=" = {symbol-completion} ";" = {symbol-completion}
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Proposal nodes
Insertion nodes
[…]
[…]
Stmt*
amb
VarDecl
ClassType
“x”
VarDecl
[…]
Assign
ID-Plhdr ;
Assign
VarRef
“x”
Exp-Plhdr ;=
Apply insertion rules at the cursor
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Limit the search space!
Exp-Plhdr Exp-Plhdr+
Assign
VarRef
“x”
;=
[…]
Add
Assign
VarRef
“x”
;=
[…]
Exp-Plhdr
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Greedy recovery!
[…]
[…]
Stmt*
amb
VarDecl
ClassType
“x”
VarDecl
[…]
Assign
ID-Plhdr ;
Assign
VarRef
“x”
Exp-Plhdr ;=
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Nested Proposal Nodes
IntValue Exp-Plhdr+
Assign
VarRef
“x”
;=
[…]
Add
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Incorrectprograms
Incompleteprograms
Completeprograms
Correctprograms
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Incorrectprograms
Incompleteprograms
Completeprograms
Expand placeholder
Correctprograms
Expand/overwrite placeholders
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Incorrectprograms
Incompleteprograms
Completeprograms
Expand placeholder
Infer placeholder
Correctprograms
Infer placeholder
Expand/overwrite placeholders
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Incorrectprograms
Incompleteprograms
Completeprograms
Expand placeholder
Infer placeholder
Correctprograms
Infer placeholder
Expand/overwrite placeholders
Recover incomplete
program
Recover completeprogram
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Language Specification
SDF3 Name Binding
Type Constraints
Code Completion
SyntacticCompletion
Semantic Completion
Sound!
Complete!
Textual IDE
