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.