Improve error handling for malformed JSON syntax

[Copilot]

Fixes #12 by properly distinguishing between malformed JSON (invalid syntax) and partial JSON (incomplete but valid syntax).

Problem

The parser was silently swallowing invalid JSON syntax instead of throwing errors:

1. Invalid numbers starting with dots - .0516156161551515 would be silently ignored, causing the rest of valid JSON to be discarded
2. Invalid tokens in arrays - [abc would return [] instead of throwing an error
3. Empty arrays with spaces - [ ] would cause parsing to terminate early, discarding subsequent valid JSON

Example

Before this fix:

parse(`{
  "vector": [1, 2, 3, .0516156161551515, 7],
  "info": "valid data"
}`)
// Returns: { "vector": [1, 2, 3] }  // Silent truncation!

After this fix:

parse(`{
  "vector": [1, 2, 3, .0516156161551515, 7],  
  "info": "valid data"
}`)
// Throws: MalformedJSON: Unexpected token '.' at position 83

Solution

1. Enhanced token validation - Added proper validation before attempting to parse numbers, rejecting invalid tokens like .123 and abc

2. Improved array parsing - Fixed whitespace handling in arrays by adding skipBlank() calls at appropriate points

3. Better error propagation - Modified parseArr() and parseObj() to let MalformedJSON errors bubble up while still allowing PartialJSON errors to be handled gracefully for incomplete but valid JSON

Backward Compatibility

✅ All existing functionality is preserved:

• Valid partial JSON parsing continues to work exactly as before
• All existing tests pass without modification
• The Allow flags continue to control partial parsing behavior as expected

This change only affects clearly invalid JSON syntax that should never have been accepted in the first place.

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Summary by CodeRabbit

• Bug Fixes

  • Improved error handling for malformed JSON, ensuring invalid numbers and tokens are correctly identified and reported.
  • Enhanced whitespace handling within arrays to ensure accurate parsing.

• Tests

  • Added comprehensive test cases to verify correct error reporting for invalid JSON inputs and to confirm proper handling of edge cases.

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commit: 9b6e38e

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Walkthrough

The changes improve JSON parsing by enhancing error handling for malformed numbers and invalid tokens, ensuring that syntax errors are no longer silently ignored. The parser now strictly validates number formats, propagates MalformedJSON errors, and adds new tests to verify that invalid input triggers errors rather than partial or incorrect parsing results.

Changes

Cohort / File(s)	Change Summary
Parser Logic Improvements src/index.ts	Refines error handling in JSON parsing: validates number start tokens, ensures MalformedJSON errors propagate, improves whitespace skipping in arrays, and makes number parsing stricter and more robust.
Tests for Issue #12 tests/issue12.test.js	Adds tests for invalid numbers and tokens, confirming that malformed input now throws MalformedJSON errors as expected and valid edge cases still parse correctly.

Sequence Diagram(s)

sequenceDiagram
    participant TestSuite as Test Suite
    participant Parser as JSON Parser
    participant Error as MalformedJSON

    TestSuite->>Parser: parse(JSON string)
    alt Valid JSON
        Parser-->>TestSuite: Return parsed object/array
    else Invalid number or token
        Parser-->>Error: Throw MalformedJSON
        Error-->>TestSuite: Error is caught and asserted
    end

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Assessment against linked issues

Objective	Addressed	Explanation
Ensure parser throws error for invalid numbers instead of silently ignoring them (#12)	✅
Prevent partial parsing when encountering malformed numbers or invalid tokens in arrays/objects (#12)	✅
Add tests to verify error reporting for invalid number formats and tokens (#12)	✅

Poem

A rabbit with code in its fur and its nose,
Digs through the JSON where error now shows.
No more silent skipping, no numbers astray—
Malformed tokens are caught, no data goes away!
With tests in the meadow and parsing made bright,
The bugs hop away, and the code feels just right.
🐇✨

[!NOTE]

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Learn more here, or try it out under "Finishing Touches" below.

✨ Finishing Touches

• [ ] 📝 Generate Docstrings

🧪 Generate unit tests

• [ ] Create PR with unit tests
• [ ] Post copyable unit tests in a comment
• [ ] Commit unit tests in branch copilot/fix-d63c1154-0fba-4921-80da-192e5f9b9723

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