Voluptuous : give error line in yaml file

Question

I am using voluptuous a lot to validate yaml description files. Often the errors are cumbersome to decipher, especially for regular users.

I am looking for a way to make the error a bit more readable. One way is to identify which line in the YAML file is incrimined.

from voluptuous import Schema 
import yaml 
from io import StringIO

Validate = Schema({
    'name': str,
    'age': int,
})

data = """
name: John
age: oops
"""

data = Validate(yaml.load(StringIO(data)))

In the above example, I get this error:

MultipleInvalid: expected int for dictionary value @ data['age']

I would rather prefer an error like:

Error: validation failed on line 2, data.age should be an integer.

Is there an elegant way to achieve this?

Answer 1

With the help of flyx I found ruamel.yaml which provide the line and col of a parsed YAML file. So one can manage to get the wanted error with:

from voluptuous import Schema 
from ruamel.yaml import load, RoundTripLoader
from io import StringIO

Validate = Schema({
    'name': {
        'firstname': str,
        'lastname': str
    },
    'age': int,
})

data = """
name: 
    firstname: John
    lastname: 12.0
age: 42
"""

class Validate:
    def __init__(self, stream):
        self._yaml = load(stream, Loader=RoundTripLoader)
        return self.validate()

    def validate(self):
        try:
            self.data = Criteria(self._yaml)
        except Invalid as e:
            node = self._yaml
            for key in e.path:
                if (hasattr(node[key], '_yaml_line_col')):
                    node = node[key]
                else:
                    break
            path = '/'.join(e.path)
            print(f"Error: validation failed on line {node._yaml_line_col.line}:{node._yaml_line_col.col} (/{path}): {e.error_message}")
        else:
            return self.data
        
data = Validate(StringIO(data))

With this I get this error message:

Error: validation failed on line 2:4 (/name): extra keys not allowed