Either/or schema validation of different, equally valid different kinds of YAML

StrictYAML can be directed to parse two different elements or blocks of YAML.

If the first thing does not parse correctly, it attempts to parse the second. If the second does not parse correctly, it raises an exception.

from strictyaml import Map, Seq, Bool, Int, Str, YAMLValidationError, load
from ensure import Ensure

schema = Str() | Map({"a": Bool() | Int()})

Boolean first choice true:

a: yes

Ensure(load(yaml_snippet, schema)).equals({"a": True})

Boolean first choice false:

a: no

Ensure(load(yaml_snippet, schema)).equals({"a": False})

Int second choice:

a: 5

Ensure(load(yaml_snippet, schema)).equals({"a": 5})

Invalid not bool or int:

a: A

load(yaml_snippet, schema)

strictyaml.exceptions.YAMLValidationError:
when expecting an integer
found arbitrary text
  in "<unicode string>", line 1, column 1:
    a: A
     ^ (line: 1)

Invalid combinations of more than one map:

a: x

load(yaml_snippet, Map({"a": Str()}) | Map({"b": Str()}))

strictyaml.exceptions.InvalidValidatorError:
You tried to Or ('|') together 2 Map validators. Try using revalidation instead.

Invalid combinations of more than one seq:

- 1
- 2

load(yaml_snippet, Seq(Int()) | Seq(Str()))

strictyaml.exceptions.InvalidValidatorError:
You tried to Or ('|') together 2 Seq validators. Try using revalidation instead.

Change item after validated:

a: yes

yaml = load(yaml_snippet, schema)
yaml['a'] = 5
assert yaml['a'] == 5

Executable specification

Documentation automatically generated from or.story storytests.