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Deep dive into Xtext scoping local and global scopes explained
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.
Deep dive into Xtext scoping local and global scopes explained
- 1. Deep dive intoXtext scoping local and global scopes explained
- 2. Sebastian Holger Who arethese guys?
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- 8. What is scoping? QualifiedName grandfather father son1 son2 -grandfather.father.son1 - grandfather.father.son2
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- 11. What is scoping? SameEMF Container
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- 13. What is scoping? PrefixMatcherdoes it’s job
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- 15. What is scoping? Notsame container
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- 23. Implicit imports Not calledfor root object!
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- 28. So far easy… Butwhat is a scope?
- 29. So far easy… Butwhat is a scope? It describes the reachable Elements…
- 30. So far easy… Butwhat is a scope? …depending on the context… It describes the reachable Elements…
- 31. So far easy… Butwhat is a scope? …depending on the context… …and maps name to EObject… It describes the reachable Elements…
- 32. So far easy… Butwhat is a scope? …depending on the context… …and maps name to EObject… …in a chain of scopes. It describes the reachable Elements…
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- 34. A chain ofresponsibility Scope EObjectDescription EObjectDescription … Scope EObjectDescription EObjectDescription … outer Index global ResourceDescription … Simply spoken
- 35. A chain ofresponsibility Scope EObjectDescription EObjectDescription … Scope EObjectDescription EObjectDescription … outer Index global ResourceDescription … Simply spoken
- 36. Index ResourceDescription … ResourceDescription URI ExportedObjects ReferencedObjects ImportedNames - Listof EObjectDescriptions - List of ReferenceDesciptions - All the names Simply spoken
- 37. Local vs. globalscoping Local
- 38. Local vs. globalscoping Local Global Other files in project and more…
- 39. Who creates Scopes? LocalScopes Global Scope aka. the Index
- 40. Who creates Scopes? LocalScopes Global Scope aka. the Index YOU! The builder!
- 41. Override getScope! Don’t usethe declarative stuff any more!
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- 55. More logic context.getField cannotbe called! CyclicLinkingException
- 56. Objects can havedifferent names in different contexts Function to transform the name The implementation creates new EObjectDescriptions
- 57. Objects can havedifferent names in different contexts org.eclipse.xtext.resource.impl.AliasedEObjectDescription org.eclipse.xtext.scoping.impl.ImportScope
- 58. Don’t create tootight scopes
- 59. Don’t create tootight scopes Use validations instead! They can produce more meaningful messages then!
- 60. The NodeModel EObject CompositeNode Adapter LeafNodeLeafNode CompositeNode LeafNode LeafNode
- 61. EObject CompositeNode Adapter LeafNode LeafNodeCompositeNode LeafNode LeafNode The NodeModel Don’trelyontheNodeModelduring scoping
- 62. Never load resourcesexplicitly There is a global scope
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- 64. Global Scoping ResourceDescriptions Constructed whenthe builder runs…
- 65. Global Scoping ResourceDescriptions Constructed whenthe builder runs… org.eclipse.xtext.resource.impl.ResourceDescriptionsProvider …accessible through… IResourceDescriptions - getResourceDescriptions(ResourceSet)
- 66. Global Scoping ResourceDescriptions Constructed whenthe 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 everythingshould be referable
- 68. Information hiding Not everythingshould 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 Longtime the was the default.
- 71. Index in Standalone ResourceSetGlobalScopeProvider Longtime 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 Fillthe index and install it on the ResourceSet! Load each resource and ask the ResourceDescriptionManager to create a ResourceDescription…
- 73. Index in Standalone Fillthe 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!