wu-sheng commented on code in PR #13723:
URL: https://github.com/apache/skywalking/pull/13723#discussion_r2883887909
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oap-server/analyzer/hierarchy/CLAUDE.md:
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@@ -0,0 +1,118 @@
+# Hierarchy Rule Compiler
+
+Compiles hierarchy matching rule expressions into `BiFunction<Service,
Service, Boolean>` implementation classes at runtime using ANTLR4 parsing and
Javassist bytecode generation.
+
+## Compilation Workflow
+
+```
+Rule expression string (e.g., "{ (u, l) -> u.name == l.name }")
+ → HierarchyRuleScriptParser.parse(expression) [ANTLR4 lexer/parser →
visitor]
+ → HierarchyRuleModel (immutable AST)
+ → HierarchyRuleClassGenerator.compile(ruleName, expression)
+ 1. classPool.makeClass() — create class implementing BiFunction
+ 2. generateApplyMethod(model) — emit Java source for apply(Object,
Object)
+ 3. ctClass.toClass(HierarchyRulePackageHolder.class) — load via package
anchor
+ → BiFunction<Service, Service, Boolean> instance
+```
+
+The generated class implements:
+```java
+Object apply(Object arg0, Object arg1)
+ // cast internally to Service and returns Boolean
+```
+
+No separate consumer/closure classes are needed — hierarchy rules are simple
enough to compile into a single method body.
+
+## File Structure
+
+```
+oap-server/analyzer/hierarchy/
+ src/main/antlr4/.../HierarchyRuleLexer.g4 — ANTLR4 lexer grammar
+ src/main/antlr4/.../HierarchyRuleParser.g4 — ANTLR4 parser grammar
+
+ src/main/java/.../compiler/
+ HierarchyRuleScriptParser.java — ANTLR4 facade: expression →
AST
+ HierarchyRuleModel.java — Immutable AST model classes
+ HierarchyRuleClassGenerator.java — Javassist code generator
+ CompiledHierarchyRuleProvider.java — SPI provider: compiles rule
expressions
+ hierarchy/rule/rt/
+ HierarchyRulePackageHolder.java — Class loading anchor (empty
marker)
+
+ src/main/resources/META-INF/services/
+ ...HierarchyDefinitionService$HierarchyRuleProvider — SPI registration
+
+ src/test/java/.../compiler/
+ HierarchyRuleScriptParserTest.java — 5 parser tests
+ HierarchyRuleClassGeneratorTest.java — 4 generator tests
+```
+
+## Package & Class Naming
+
+| Component | Package / Name |
+|-----------|---------------|
+| Parser/Model/Generator |
`org.apache.skywalking.oap.server.core.config.compiler` |
+| Generated classes |
`org.apache.skywalking.oap.server.core.config.compiler.hierarchy.rule.rt.HierarchyRule_<N>`
|
+| Package holder |
`org.apache.skywalking.oap.server.core.config.compiler.hierarchy.rule.rt.HierarchyRulePackageHolder`
|
+| SPI provider |
`org.apache.skywalking.oap.server.core.config.compiler.CompiledHierarchyRuleProvider`
|
Review Comment:
Fixed. Updated all four paths to include the `.v2.` segment.
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