[SAOC 2025] Improving D Error Messages Weekly Update #4

Development of ErrorSinkJSON

• Modified the new error sink class ErrorSinkJSON derived from ErrorSink.
• Designed to output compiler diagnostics (errors, warnings, deprecations) in JSON format.
• Created printJSONObject() method to print diagnostic in JSON format directly to stdout.
• Work under progress for the unittests for errorsinkjson.d

Challenges Encountered

• Resolving @safe vs @system issues when using vfprintf/vsnprintf.
• Handling null filenames safely in JSON output.
• Ensuring proper import paths to resolve dmd.errorsink without creating cycles.

Work in : https://github.com/Iskaban10/dmd/tree/lsp