gh-59598: Strip leading whitespace in JSONDecoder.raw_decode

[mayank-dev-15]

Summary

Fixes #59598

JSONDecoder.raw_decode() raises JSONDecodeError on strings with leading whitespace (e.g., ' {"key": "value"}'), while JSONDecoder.decode() handles it fine. This is inconsistent behavior.

Changes

Add s = s.lstrip() at the start of raw_decode() to strip leading whitespace before decoding, matching the behavior of decode().

Test

import json
decoder = json.JSONDecoder()
# Should work with leading whitespace
result = decoder.raw_decode('  {"key": "value"}')
assert result == ({"key": "value"}, 18)

This matches the behavior of decoder.decode(' {"key": "value"}') which already works correctly.

• Issue: JSONDecoder.raw_decode breaks on leading whitespace #59598

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