Description

@slyon thanks for the jira ping.
Request for comment as to whether this is the right approach to take to get more detailed schema errors (we could alternatively look to unique err.contents.code differences from the C library but we'd also still have to 'unpack' some encoded line/column and path values from the structured error messages in python.

Cloud-int would like to have specialized exception types from libnetplan for schema errors. The specialization needed would be attributes on the Exception raised which point to the offending config file path, the marked error line number and column number.

It seems that all libnetplan errors are generalized from the GERROR raised by the C code. If we can either specialize the err.contents.code for different types or errors, or allow for message format parsing in libnetplan:_checked_lib_call then cloud-init error handling and reporting from tooling can better know how to handle schema errors vs other errors raised by netplan.

mkdir /tmp/netplan
cat > /tmp/new.yaml <<EOF
network: bogus
EOF

cat > validate_bogus_netplan.py <<EOF
from netplan import libnetplan

ROOT_DIR="/tmp/netplan"
def doit():
    parser = libnetplan.Parser()
    parser.load_yaml_hierarchy(ROOT_DIR)
    try:
        parser.load_yaml("/tmp/new.yaml")
    except LibNetplanException as e: # cloud-init wants a LibNetplanSchemaException if possible
        print(dir(e))   # cloud-init doesn't want to parse the structured e.message to tease out line and column info

if __name__ == "__main__":
    doit()
EOF

PYTHONPATH=/usr/share/netplan python3 validate_bogus_netplan.py

Checklist

• Runs make check successfully.
• Retains 100% code coverage (make check-coverage).
• New/changed keys in YAML format are documented.
• (Optional) Adds example YAML for new feature.
• (Optional) Closes an open bug in Launchpad.