Slides for the MoDELS'16 (http://models2016.irisa.fr/) tutorial on creating new languages for the Epsilon (https://www.eclipse.org/epsilon/) platform.

1. MoDELS 2016 Advanced Model Management with EpsilonAdvanced Model Management with EpsilonMoDELS 2016
Developing a new Epsilon
Language through Annotations:
TestLang
Antonio Garcia-Dominguez
@antoniogado
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2. MoDELS 2016 Advanced Model Management with Epsilon
When should I use annotations?
• One of the Epsilon languages does almost
everything that you need, but…
• … you need to add a thin layer of
orchestration logic on top of it.
• Some examples:
– Unit testing (EOL + orchestration)
– Model generation (EOL + ...)
– Model mutation (EOL/ETL + ...)
– Categorized model validation (EVL + ...)
– Model-driven game engine...
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3. MoDELS 2016 Advanced Model Management with Epsilon
Example TestLang script (v1)
var rnd = new Native('java.util.Random');
@test
operation allInstancesWorks() {
if (Class.all.size != 6) { “FAILED aiw”.println(); }
}
@test
$times 10 * 10
operation randomTest() {
var b = 2 + rnd.nextInt(9); var e = rnd.nextInt(10);
if (slowPow(b, e) != fastPow(b, e)) { “FAILED rt”.println(); }
} 3

4. MoDELS 2016 Advanced Model Management with Epsilon
Overview
• TestLang is divided into:
– org.eclipse.epsilon.examples.testlang.engine
implements the language (Eclipse-agnostic)
– org.eclipse.epsilon.examples.testlang.dt
provides Eclipse dev tools
• Sources here:
– https://git.eclipse.org/c/epsilon/org.eclipse.e
psilon.git/tree/examples
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5. MoDELS 2016 Advanced Model Management with Epsilon
TESTLANG EXECUTION ENGINE
Implementing a simple unit testing language on top of EOL
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6. MoDELS 2016 Advanced Model Management with Epsilon
TestLangModule: execution engine
● Inherits from EolModule, overrides methods
○ execute(): interprets @test and $times
● 68 lines of Java code
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7. MoDELS 2016 Advanced Model Management with Epsilon
AnnotatableModuleElement
• Superclass of anything that can be annotated
– EOL operations
– ETL rules
– EVL contexts and constraints...
• Two types of annotations supported:
– Simple: “@test a” - constant value
– Executable: “$test self.x * 2” - uses expression
– Repeated annotations are allowed
• Provides methods for handling annotations
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8. MoDELS 2016 Advanced Model Management with Epsilon
Example TestLang script (v2)
var rnd = new Native('java.util.Random');
@test
operation allInstancesWorks() { areEqual(6, Class.all.size); }
@test
$times 10 * 10
operation randomTest() {
var base = 2 + rnd.nextInt(9);
var exp = rnd.nextInt(10);
areEqual(slowPow(base, exp), fastPow(base, exp));
}
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9. MoDELS 2016 Advanced Model Management with Epsilon
TestLangModule: add areEqual
● By overriding prepareContext(), we can add
task-specific operations/variables
● Operations provided by OperationContributor
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10. MoDELS 2016 Advanced Model Management with Epsilon
Operation contributors
• When processing x.f(args):
– contributesTo(x) must return true
– f(args) must be a method of the contributor
• Contextless operations (e.g. “areEqual”)
receive a special value in contributesTo:
– EolNoType.NoInstance
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11. MoDELS 2016 Advanced Model Management with Epsilon
TESTLANG ECLIPSE-BASED
DEVELOPER TOOLS
Integration of TestLang into Eclipse
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12. MoDELS 2016 Advanced Model Management with Epsilon 12

13. MoDELS 2016 Advanced Model Management with Epsilon
TestLang developer tools
• Same approach as the engine: inherit from
common.dt / eol.dt and refine as desired
– 65 lines of Java code
• plugin.xml (49 lines):
– Integrates all our subclasses
– Associates .eolt with the “New TestLang” wizard
– Reuses EOL editor/debugger for .eolt files
– Provides a custom icon for .eolt launch configs
• In short: mostly plumbing!
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14. MoDELS 2016 Advanced Model Management with Epsilon
TestLang editor: same as EOL
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15. MoDELS 2016 Advanced Model Management with Epsilon
TestLang launch facilities
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16. MoDELS 2016 Advanced Model Management with Epsilon
Summary
• Showed how to implement a unit testing
language on top of EOL:
– @test tags an operation as a test case
– $times allows for repeating the same test
• Reuses all EOL tooling:
– Editor and debugger “for free”
– Can work with EMF, CSV, BibTeX, XML, ...
• < 200 lines of code: 133 Java, 49 XML
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17. MoDELS 2016 Advanced Model Management with EpsilonAdvanced Model Management with EpsilonMoDELS 2016
Questions?
@antoniogado
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18. MoDELS 2016 Advanced Model Management with Epsilon
Other examples
@operator
$condition self.isKindOf(Addition)
operation add2sub() {
// … return Subtraction
}
@operator
$condition self.isKindOf(BooleanLiteral)
operation flipLiteral() {
// … return negated BooleanLiteral
}
For a model mutation language:
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19. MoDELS 2016 Advanced Model Management with Epsilon
Other examples
@enemy
@after blinky
@sprite red_ghost.png
operation inky(player, enemies) {
// … compute which way to turn next …
// … compute speed …
}
In a model-driven game engine, operations could provide
behavior for AI actors:
The language can provide built-in operations for
common/expensive tasks (e.g. pathfinding algorithms).
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