Reader/Writer runtime exceptions could be more useful

[naegelejd]

Currently, exceptions in the generated code are all thrown as runtime errors (RuntimeError in python, std::runtime_error in c++). For example, when reading a binary stream:

yardl/tooling/internal/python/static_files/_binary.py

Lines 80 to 89 in ba89cf7

	if magic_bytes != MAGIC_BYTES: # pyright: ignore [reportUnnecessaryComparison]
	raise RuntimeError("Invalid magic bytes")
	version = read_fixed_int32(self._stream)
	if version != CURRENT_BINARY_FORMAT_VERSION:
	raise RuntimeError("Invalid binary format version")
	self._schema = string_serializer.read(self._stream)
	if expected_schema and self._schema != expected_schema:
	raise RuntimeError("Invalid schema")

These would be more useful if they were library-defined exceptions.

For example, using mrd, if someone attempts to use a mrd.BinaryReader to open an invalid file in Python, the user will see the following:

Traceback (most recent call last):
  ...
    with mrd.BinaryMrdReader(args.input_file) as reader:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/uv/.venv/lib/python3.12/site-packages/mrd/binary.py", line 49, in __init__
    _binary.BinaryProtocolReader.__init__(self, stream, MrdReaderBase.schema)
  File "/opt/uv/.venv/lib/python3.12/site-packages/mrd/_binary.py", line 81, in __init__
    raise RuntimeError("Invalid magic bytes")
RuntimeError: Invalid magic bytes

Instead, the Python program that opens the binary reader could catch a mrd.InvalidMagicBytes exception, and print a helfpul error message, such as "Invalid file, are you sure it is in MRD format?"...

I vote we replace these runtime errors with custom exceptions that can be better handled downstream. This applies to the generated C++ and MATLAB code as well.

[naegelejd]

This applies also to the schema check. If a user tries to read a file created using an older version of the model, all they see on the command-line is RuntimeError: Invalid schema, which is not helpful.