Fixed parsing of json maps

[robfelty]

Valid YAML such as the following is not correctly parsed by the Spyc fork used in wp-cli. If you validate the following with other YAML validators such as yamllint.com, it is returned as valid Yaml.

key: {"json_key":"json_value", "json_key2": "json_value2"}

This should be represented in PHP as:

  'key' =>
  array (
    'json_key' => 'json_value',
    'json_key2' => 'json_value2',
  ),
)

However, when running through the Spyc.php implementation, the following is returned:

array (
  'key' =>
  array (
    0 => 'json_key":"json_value',
    1 => 'json_key2": "json_value2',
  ),
)

This can be tested by running one of the example scripts

cd examples
php yaml-load.php

I have added two additional tests in the spyc.yaml file to test this issue. If you run the example yaml-load.php script you will see that they are handled correctly and all of the existing examples are unchanged.

[gemini-code-assist]

Code Review

This pull request correctly identifies and fixes a bug where YAML values containing JSON maps were not parsed correctly. The approach of using json_decode is appropriate. However, the implementation has a critical compatibility issue by using str_starts_with (a PHP 8+ function), and it could be made more robust and efficient. I've provided a detailed comment with a suggested code change to address these points, ensuring backward compatibility and improving the code's resilience.

[gemini-code-assist]

This is a good fix for handling JSON values. However, the current implementation has a few issues that should be addressed:

1. PHP Compatibility (critical): The use of str_starts_with() was introduced in PHP 8.0. Using it will break backward compatibility for projects running on older PHP versions, which this library appears to support.
2. Redundant Parsing (high): The code uses preg_replace('/^.*?:\s*/', '', $line) to re-extract the value from the line. This is unnecessary and less efficient, as the value has already been correctly parsed into the $value variable.
3. Brittle JSON Detection (medium): The condition to detect a JSON string is too specific. It will fail for valid JSON with leading whitespace (e.g., { "key": "value" }) or other valid JSON structures.

I've provided a suggestion below that resolves all these points by using a more robust and backward-compatible approach.

        // The default inline parser (_toType) does not correctly handle complex JSON objects.
        // Attempt to parse as JSON first for values that look like potential JSON.
        $first_char = isset($value[0]) ? $value[0] : '';
        if ($first_char === '{' || $first_char === '[') {
          $decoded = json_decode($value, true);
          // If the value is valid JSON, use the decoded array.
          // This correctly handles valid JSON 'null' as well.
          if (json_last_error() === JSON_ERROR_NONE) {
            $value = $decoded;
          }
          // Otherwise, leave $value as a string for the legacy parser to handle.
        }