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Reference Material
- https://github.com/antlr/antlr4/blob/master/doc/getting-started.md
- https://pragprog.com/titles/tpantlr2/the-definitive-antlr-4-reference/#resources
- https://alexecollins.com/antlr4-and-maven-tutorial/
- https://tomassetti.me/antlr-mega-tutorial/
IntelliJ Ant plugin
- useful https://github.com/antlr/intellij-plugin-v4 useful for testing and troubleshooting while developing grammar
...
Findings
- Antlr4 can replace regex with less and more readable code
- Replacement of regex for
CpsPathQueryfully replaced by fully compatible object generated using Antlr4 this commit: https://gerrit.onap.org/r/c/cps/+/121503 - Needed to add explicit error rule for handling unexpected tokens (otherwise Antlr would ignore them):
ErrorCharacter : . ; - Current CPS code using regex is inconsistent and needless limited for single leave condition
- Current code was lac re. @ for attribute names (fixed in https://gerrit.onap.org/r/c/cps/+/121503)
CpsPathQuerySpecdid not cover all necessary possibilities (as used in some DB integration tests) This has now been addressedCpsDataPersistenceQueryDataNodeSpeccontains some grammar tests that should be (are already) inCpsPathQuerySpec- IntelliJ plugin very useful for quick testing and troubleshooting of grammar
- Not sure of best way to refresh generated code (in IntelliJ)
mvn clean installin cps-path-parser seems the surest way
To-Do
- Check and Improve error handling
- Re-use CpsPath Exception (wrap IllegalState exception)
- Clean up, simplify rules and remove redundant legacy limitations
- Consider using predefined xpath grammer: https://github.com/antlr/
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- grammars-v4/tree/master/xpath/xpath31
- Even just study it or extract small parts to get correct definition of valid container-names etc.