test-parser-jdk

dhamidi's avatarfrom dhamidi

Test the Java parser by parsing JDK source files and fixing parse errors. Use when asked to find/fix parse errors, test the parser, or improve JDK compatibility.

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[Testing and QA]

When & Why to Use This Skill

This Claude skill provides a comprehensive framework for testing and debugging Java parsers using authentic JDK source files. It streamlines the identification of syntax incompatibilities and parse errors, ensuring high-level JDK compatibility and support for modern Java features like switch expressions, record patterns, and sealed classes.

Use Cases

  • Scenario 1: Improving JDK compatibility by running the parser against the entire JDK source tree to identify unhandled syntax patterns and edge cases.
  • Scenario 2: Debugging specific parse errors by isolating line-level failures in complex Java files and verifying fixes in real-time.
  • Scenario 3: Validating support for modern Java language features (Java 17-21+) such as pattern matching, records, and sealed classes through targeted testing.
  • Scenario 4: Regression testing for Java-based static analysis tools to ensure that parser updates do not break existing syntax support.
nametest-parser-jdk
descriptionTest the Java parser by parsing JDK source files and fixing parse errors. Use when asked to find/fix parse errors, test the parser, or improve JDK compatibility.

Test Parser with JDK Sources

Overview

This skill helps identify and fix parse errors in the Java parser by running it against JDK source files in testcases/jdk/.

Commands

Run the JDK parse test

go test -v -run TestParseJDKSourceFiles ./java/parser/ 2>&1 | grep -c "parse error"

This shows the total count of files with parse errors.

List files with parse errors

go test -v -run TestParseJDKSourceFiles ./java/parser/ 2>&1 | grep "parse error" | head -20

Parse a specific file and show errors

go run ./cmd/javalyzer parse <file> 2>&1 | grep -i "error"

Example:

go run ./cmd/javalyzer parse testcases/jdk/java.base/java/io/ObjectStreamClass.java 2>&1 | grep -i "error"

Workflow for Fixing Parse Errors

  1. Identify a failing file: Run the test and pick the first file with errors
  2. Find the error location: Parse the file and grep for "ERROR:" to see line numbers
  3. Read the problematic code: Use Read tool to examine the Java syntax at that location
  4. Understand the syntax: Identify which Java language feature isn't being parsed
  5. Fix the parser: Edit java/parser/parser.go to handle the syntax
  6. Verify the fix: Re-parse the file to confirm errors are gone
  7. Run full test: Check the total error count decreased
  8. Commit: Use git commit --no-verify -m "parser: <description of fix>"

Common Parse Error Patterns

  • Switch expressions: case null, default -> (Java 21)
  • Array type method references: String[]::new, Class<?>[]::new
  • Pattern matching: case String s ->
  • Record patterns: case Point(int x, int y) ->
  • Sealed classes: sealed class, permits

Key Parser Files

  • java/parser/parser.go - Main parser implementation
  • java/parser/grammar.ebnf - Grammar reference
  • java/parser/lexer.go - Token definitions

Example Error Output

Error [314:24-314:31] ERROR: expected expression

This means at line 314, columns 24-31, the parser expected an expression but found something unexpected.