Domain-Specific Languages for Composable Editor Plugins (LDTA 2009)

Domain-Specific Langua ges for
Composable Editor Plugins

LDTA 2009, York, UK

Lennart Kats (me), Delft University of Technology
Karl Trygve Kalleberg, University of Bergen
Eelco Visser, Delft University of Technology
March 19, 2009

Software Engineering Research Group

The Framework
is the
Language

Implementing IDEs:
The Two Faces of Eclipse

Eclipse platform:
• Cross-platform, open-source
• People have it
• People use it
• Java, ...

Implementing IDEs:

Huge, low-level API
• SWT widgets
• synchronization
• I/O
• regexes

Implementing IDEs:

Weakly typed interfaces
• XML
• java.lang.Object, IAdaptable
• CoreException
"A checked exception representing a failure."

DSLs and Language Extensions

Domain-specific void browse() {
List<Book> books =
• Database queries
<| SELECT *
• Regular expressions FROM books
• XML processing WHERE price < 100.00
|>;
• Matrices
• Complex numbers …
• ...
for (int i = 0; i < books.size(); i++)
books.get(i).title =~ s/^The //;
}

Meta-programming with
Concrete Object Syntax
• Program transformation
• Stratego with WebDSL, Java, XML

webdsl-action-to-java-method:
|[ action x_action(farg*) { stat* } ]| ->
|[ public void x_action(param*) { bstm* } ]|
with param* := <map(action-arg-to-java)> farg*;
bstm* := <statements-to-java> stat*

IDE development environments
(Or: How to Learn to Stop Worrying and Love Eclipse)

• Abstraction
• avoid Eclipse framework complexity
• Modularity
• separation of concerns
• reuse
• Extensibility and customization
• integration with existing compilers, tools

Introducing Spoofax/IMP

• Three pillars:
• SDF grammars
• DSLs for service descriptors
• Implemented using
Spoofax and IMP frameworks (“SAFARI”)

An IDE plugin created with Spoofax/IMP

SDF and SGLR (1)

• Unified lexical and context-free syntax

module WebDSL
imports MixHQL[HQL] AccessControl ...
exports
lexical syntax
[a-zA-Z][a-zA-Z0-9_]* → Id
...
context-free syntax
"module" Id Section* → Unit {cons("Module")}
"section" SectionName Def* → Section {cons("Section")}
"define" Mod* Id "{" Element* "}" → Def {cons("SimpleDef")}
...

SDF and SGLR (2)

• Scannerless Generalized-LR Parsing
• Full class of context-free grammars
• Compositional
• Declarative disambiguation filters

module Stratego-WebDSL-Java-XML
imports
Stratego-Java-15
Stratego-WebDSL
Stratego-XML

Modular Editor Service Definitions

• Main file
• Definition for each service
• Generated definitions

Reuse and Modularity in IDE plugins

Stratego + WebDSL editor =
StrategoWebDSL editor

• Declarative specifications
• (Backdoor available)

Creating a brand new IDE plugin

Requires: Gives you:
• Syntax definition • Service templates
• Language name • Generated services
• File extension(s) • plugin.xml, ...

And:
• Basic IDE functionality:
Coloring, outline, folding

In the Beginning: WebDSL.main.esv
module WebDSL.main

imports
WebDSL-Analysis WebDSL-Colorer WebDSL-...

language Description

name : WebDSL
aliases : WebDiesel
id : org.strategoxt.imp.generated.webdsl

description : "Spoofax/IMP-generated editor for the WebDSL language"
url : http://strategoxt.org

language Files and parsing

[...]

In the Beginning: WebDSL.main.esv
module WebDSL.main

imports
WebDSL-Analysis WebDSL-...
WebDSL-Colorer WebDSL-...

language Description

[...]

language Files and parsing

extensions
[...] : app
table : include/WebDSL.tbl
start symbols : Unit

In the Beginning (2): Generated Services
• Based on heuristics
• Rapid prototyping
• Starting point
• functioning as an example
• self-documenting

module WebDSL-Colorer.generated

// ...documentation...

colorer Default highlighting rules
keyword : "Keywords" = magenta bold
string : "Strings" = blue
number : "Numbers" = darkgreen
...

Example: The colorer service
module Stratego-WebDSL-Colorer

imports
Stratego
WebDSL

colorer Variables

_.Var : green italic

colorer Concrete syntax

environment _.ToMetaExpr:
_ gray

environment _.FromMetaExpr:
_ white

Example: The folding service
module Java-Folding

imports
Java-Folding.generated

folding Customization

CompilationUnit
NewInstance
QNewInstance

ImportDec* (folded)
Block (disable)

Syntactic Editor Services

• Syntax errors
• Code folding
• Outline view
• Brace matching
• Comments
• Source code formatting

Semantic Editor Services

• Error reporting
• Reference resolving
• Reference info
• Occurrence highlighting

Stratego integration

Stratego:
• Rewrite rules
• Strategies to control
their application
• Used for e.g., WebDSL, Stratego, Java [OOPSLA'08]

Interfacing with Stratego
• Interface based on rewrite rules
• Adapted primitives for parsing, caching

Offending term + message tuples
[(Var(“auhtor”), “undeclared”), ...]

editoranalyze:
  (ast, path, fullpath) > (errors, warnings, infos)
  with
    ...
    (errors, warnings, infos) := <collectallmarkers> ast
    ...

Interfacing with Stratego
• Interface based on rewrite rules
• Adapted primitives for parsing, caching

Referenced declaration
Property(“author”, ...)

referenceresolve:
  (ast, path, fullpath, reference) > declaration
  with
    ...
    declaration := <finddecl> reference
    ...

Using Stratego:
A Global-to-Local Transformation
entity User {
username :: String (id) entity User {
password :: Secret username :: String (id)
isAdmin :: Bool password :: Secret
} isAdmin :: Bool
normalize name :: String
manager -> User
extend entity User { employees -> Set<User>
name :: String }
manager -> User
employees -> Set<User>
}

Term Rewriting with Origin Tracking
[Van Deursen et al 1993]

entity User {
username :: String (id) entity User {
password :: Secret username :: String (id)
isAdmin :: Bool password :: Secret
} isAdmin :: Bool
normalize name :: String
manager -> User
extend entity User { employees -> Set<User>
name :: String }
manager -> User
employees -> Set<User>
}

Program Object Model (POM) adapter
[Kalleberg et al, LDTA'07]

Interpret term operations as API calls
• Using Spoofax interpreter
• Intercept applications of rewrite rules
in strategies
• Override term building, 'all', 'some', and 'one'
for origin tracking

Dynamic Building and Loading:
The Editor Service Builder
• Verifies all service descriptors
• Syntax
• Existing sorts
• ...
• Updates plugin.xml, etc.
• Builds parse tables

Dynamic Building and Loading:
Dynamically Loading Editor Services
<<language>>
• IMP provides: DynamicRoot
DynamicColor : Colorer
• static, XML-based dynamicFolder : Folder
editor declarations ...

• language inheritance
<<language>>
WebDSL
• Base language
• Defines default services
• May be overridden
by dynamic or “backdoor” implementations

Looking back

LDTA'07: Spoofax

Embedded Java code

Looking back

LDTA'08: sdf2imp

No:
• Semantic services
• Dynamic loading
• Modular definitions

Looking forward (to)

• Complete Stratego-based DSL environment
• compiler for Java
• SDF bundle
• Expansion of editor services
• e.g. content completion

Looking forward (to)

• Integration with Aster [CC 2009]
• Better interactive parser
• performance
• error handling
• content completion

Concluding Remarks
• Declarative DSLs
• Avoid Eclipse API complexity
• Specialized syntax
• Compositionality
• Co-evolution of language and IDE

DomainSpecific Languages for Composable Editor Plugins.
Lennart C. L. Kats, Karl T. Kalleberg, and Eelco Visser. LDTA 2009.

http://www.strategoxt.org/Stratego/SpoofaxIMP

Domain-Specific Languages for Composable Editor Plugins (LDTA 2009)

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