feat: introduce maximum parser recursion depth

[ronantakizawa]

Resolves issue #473.

This PR implements a configurable maximum parser recursion depth limit to prevent stack overflow from deeply
nested Jsonnet structures, following the approach from google/jsonnet#1230

Changes

• Added maxParserRecursionDepth: Int = 1000 parameter to Settings class
• Added --max-parser-recursion-depth CLI argument to allow runtime configuration
• Updated Settings flow: CLI → Config → Settings → Interpreter → CachedResolver → Parser

Before:

• Parsing extremely deeply nested structures (e.g., [[[...1000+ levels...]]]) could cause native stack
  overflow and crash the interpreter.

After:

• Parser gracefully throws java.lang.Exception: Parsing exceeded maximum recursion depth of 1000 instead of
  crashing.
• Users can now configure the limit: sjsonnet --max-parser-recursion-depth 2000 deeply_nested.jsonnet
• Allows tuning for specific use cases while maintaining safe defaults

[He-Pin]

Better we can set this with the setting

[ronantakizawa]

@He-Pin I implemented the fix, but let me know if I should remove some uses of checkParseDepth for performance purposes (Checking parse depth too much can slow down performance.)

[He-Pin]

@ronantakizawa I think so , we should not slow the parsing much.

[ronantakizawa]

@He-Pin @stephenamar-db implemented feedback.
checkParseDepth is now only used for:

1. arr method (line 201) - protects array parsing recursion
2. expr method (line 265) - protects main expression parsing recursion
3. climb method (line 270) - protects binary operator precedence climbing recursion
4. objinside method (line 479) - protects object parsing recursion

Previously it was used for 27 other methods.

1. compSuffix - comprehension suffix parsing
2. arrBody - array body parsing
3. assertExpr - assertion expression parsing
4. function - function definition parsing
5. ifElse - if-else expression parsing
6. localExpr - local expression parsing
7. expr1 - expression level 1 parsing
8. exprSuffix2 - expression suffix parsing
9. local - local binding parsing
10. importStr - import string parsing
11. importBin - import binary parsing
12. import - import parsing
13. error - error expression parsing
14. importExpr - import expression parsing
15. unaryOpExpr - unary operator parsing
16. expr2 - expression level 2 parsing
17. member - object member parsing
18. field - object field parsing
19. objlocal - object local parsing
20. compspec - comprehension spec parsing
21. forspec - for specification parsing
22. ifspec - if specification parsing
23. fieldname - field name parsing
24. assertStmt - assertion statement parsing
25. bind - binding parsing
26. args - arguments parsing
27. params - parameters parsing

[stephenamar-db]

Hi @lihaoyi, if I have time of course, I would appreciate if you could take a this PR. I'm trying to figure out if this is right way to implement maximum parse recursion depth with fastparse.

[lihaoyi]

@stephenamar-db the implementation looks fine. FastParse "rules" are just methods, so passing around a currentDepth: Int is a totally reasonable thing to do. An alternative would be to put the data in the ParsingRun#misc dictionary, or just use a ThreadLocal, both of which would reduce the verbosity but trade off explicitness. Either approach works fine, so the current code works if you don't have a preference.

Only comment I would give is that I think a single checkParseDepth call inside def objinside is unnecessary, as any recursion would have to go through def expr anyway. But I guess it depends on how fine-grained you want checkParseDepth to be. In theory you should check every time you increment currentDepth + 1 if you want overshoots to be caught precisely, but if all you want to do is avoid infinite recursion then only checking in def expr` is enough

[He-Pin]

@ronantakizawa climb method (line 270) - protects binary operator precedence climbing recursion

This may not needed, I think the we should only limit where (), {}, [] nesting, not sure about the long binary operations

[ronantakizawa]

@He-Pin @lihaoyi implemented fixes!

Now only arr and expr has checkParseDepth