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indexing_and_psi_stubs.md: clarify "light AST"

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Yann Cébron 2022-03-15 12:16:51 +01:00
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topics/basics/indexing_and_psi_stubs.md
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@ -64,15 +64,16 @@ These are additionally available in HTML format starting with 2021.1.
Use [lexer](implementing_lexer.md) information instead of parsed trees if possible.
If impossible, use light AST which doesn't create memory-hungry AST nodes inside, so traversing it might be faster.
Obtain [`LighterAST`](upsource:///platform/core-api/src/com/intellij/lang/LighterAST.java) by casting `FileContent` input parameter to [`PsiDependentFileContent`](upsource:///platform/core-api/src/com/intellij/util/indexing/PsiDependentFileContent.java) and calling `getLighterAST()`.
Make sure to traverse only the nodes you need to.
For indexing XML, also consider using [`NanoXmlUtil`](upsource:///platform/indexing-impl/src/com/intellij/util/xml/NanoXmlUtil.java).
See also [`LighterASTNodeVisitor`](upsource:///platform/core-impl/src/com/intellij/psi/impl/source/tree/LighterASTNodeVisitor.java) and [`LightTreeUtil`](upsource:///platform/core-impl/src/com/intellij/psi/impl/source/tree/LightTreeUtil.java) for useful utility methods.
For stub index, implement [`LightStubBuilder`](upsource:///platform/core-impl/src/com/intellij/psi/stubs/LightStubBuilder.java).
For other indexes, you can obtain the light AST manually via `((PsiDependentFileContent) fileContent).getLighterAST()`.
If a custom language contains lazy-parseable elements that never or rarely contain any stubs, consider implementing `StubBuilder.skipChildProcessingWhenBuildingStubs()` (preferably using Lexer/node text).
For indexing XML, also consider using [`NanoXmlUtil`](upsource:///platform/indexing-impl/src/com/intellij/util/xml/NanoXmlUtil.java).
### Consider Prebuilt Stubs
If your language has a massive standard library, which is mostly the same for all users, you can avoid stub-indexing it in each installation by providing prebuilt stubs with your distribution.