Deep dive into Xtext scoping local and global scopes explained
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This document discusses scoping in Xtext, including local versus global scoping, how scopes are created, and some best practices when working with scopes. Key points include: - Scopes describe the reachable elements in a given context and map names to EObjects. - Local scopes are created by language developers while the global scope (index) tracks elements across resources. - Language builders override getScope() to define scoping logic. Avoid cyclic references when collecting elements. - The global index tracks exported elements from resource descriptions to enable cross-file references. - Best practices include using user data instead of resolving proxies, validating instead of tight scoping, and avoiding direct resource loading.
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Deep dive into Xtext scoping local and global scopes explained
- 1. Deep dive into Xtext scoping local and global scopes explained
- 2. Sebastian Holger Who are these guys?
- 8. What is scoping? QualifiedName grandfather father son1 son2 - grandfather.father.son1 - grandfather.father.son2
- 9. What is scoping? Simple name
- 10. What is scoping?
- 11. What is scoping? Same EMF Container
- 12. What is scoping?
- 13. What is scoping? PrefixMatcher does it’s job
- 14. What is scoping?
- 15. What is scoping? Not same container
- 16. Imports?
- 20. Implicit imports
- 21. Implicit imports
- 22. Implicit imports
- 23. Implicit imports Not called for root object!
- 24. Implicit imports
- 25. Implicit imports
- 26. Implicit imports
- 27. So far easy…
- 28. So far easy… But what is a scope?
- 29. So far easy… But what is a scope? It describes the reachable Elements…
- 30. So far easy… But what is a scope? …depending on the context… It describes the reachable Elements…
- 31. So far easy… But what is a scope? …depending on the context… …and maps name to EObject… It describes the reachable Elements…
- 32. So far easy… But what is a scope? …depending on the context… …and maps name to EObject… …in a chain of scopes. It describes the reachable Elements…
- 33. Simply spoken Scope EObjectDescription EObjectDescription … EObjectDescription QualifiedName URI UserData
- 34. A chain of responsibility Scope EObjectDescription EObjectDescription … Scope EObjectDescription EObjectDescription … outer Index global ResourceDescription … Simply spoken
- 35. A chain of responsibility Scope EObjectDescription EObjectDescription … Scope EObjectDescription EObjectDescription … outer Index global ResourceDescription … Simply spoken
- 36. Index ResourceDescription … ResourceDescription URI ExportedObjects ReferencedObjects ImportedNames - List of EObjectDescriptions - List of ReferenceDesciptions - All the names Simply spoken
- 37. Local vs. global scoping Local
- 38. Local vs. global scoping Local Global Other files in project and more…
- 39. Who creates Scopes? Local Scopes Global Scope aka. the Index
- 40. Who creates Scopes? Local Scopes Global Scope aka. the Index YOU! The builder!
- 41. Override getScope! Don’t use the declarative stuff any more!
- 42. Simple Example
- 43. Simple Example
- 44. Simple Example
- 48. More logic
- 52. More logic
- 53. More logic
- 54. More logic
- 55. More logic context.getField cannot be called! CyclicLinkingException
- 56. Objects can have different names in different contexts Function to transform the name The implementation creates new EObjectDescriptions
- 57. Objects can have different names in different contexts org.eclipse.xtext.resource.impl.AliasedEObjectDescription org.eclipse.xtext.scoping.impl.ImportScope
- 58. Don’t create too tight scopes
- 59. Don’t create too tight scopes Use validations instead! They can produce more meaningful messages then!
- 60. The NodeModel EObject CompositeNode Adapter LeafNode LeafNode CompositeNode LeafNode LeafNode
- 61. EObject CompositeNode Adapter LeafNode LeafNode CompositeNode LeafNode LeafNode The NodeModel Don’trelyontheNodeModelduring scoping
- 62. Never load resources explicitly There is a global scope
- 63. Global Scoping
- 64. Global Scoping ResourceDescriptions Constructed when the builder runs…
- 65. Global Scoping ResourceDescriptions Constructed when the builder runs… org.eclipse.xtext.resource.impl.ResourceDescriptionsProvider …accessible through… IResourceDescriptions - getResourceDescriptions(ResourceSet)
- 66. Global Scoping ResourceDescriptions Constructed when the builder runs… org.eclipse.xtext.resource.impl.ResourceDescriptionsProvider …accessible through… IResourceDescriptions - getResourceDescriptions(ResourceSet) …depending on the LoadOptions… LIVE_SCOPE NAMED_BUILDER_SCOPE
- 67. Information hiding Not everything should be referable
- 68. Information hiding Not everything should be referable Save memory and time!
- 69. EObjectDescription(QualifiedName qualifiedName, EObject element, Map<String, String> userData) UserData Serializable stuff Informations without resolving the proxy
- 70. Index in Standalone ResourceSetGlobalScopeProvider Long time the was the default.
- 71. Index in Standalone ResourceSetGlobalScopeProvider Long time the was the default. Today we can do better but you need to use it and know that there is something new… For Maven- and Gradle it’s done.
- 72. Index in Standalone Fill the index and install it on the ResourceSet! Load each resource and ask the ResourceDescriptionManager to create a ResourceDescription…
- 73. Index in Standalone Fill the index and install it on the ResourceSet! Load each resource and ask the ResourceDescriptionManager to create a ResourceDescription… Install it on the ResourceSet
- 74. Lessons learned Never use #getResource Avoid the Node Model CyclicResolutionExceptions! UserData helps Never use #getResource! Don’t Filter - But Validate!