Support request: How to formulate a schema containing partially exclusive or without Or?

I’ve a config which is partially exclusive OR. It may be either like this

common:
- ...
variant_a:
- ...
variant_a_again:
- ...

or

common:
- ...
variant_b:
- ...
variant_b_again:
- ...

Using a schema like schema = Map({"common": Seq(...), "variant_a": Seq(...), "variant_a_again": Seq(...)}) | Map({"common": Seq(...), "variant_b": Seq(...), "variant_b_again": Seq(...)}) should work. However I get this error strictyaml.exceptions.InvalidValidatorError: You tried to Or ('|') together 2 Map validators. Try using revalidation instead. which prevents me from using it. To me it’s not clear how to do revalidation here. How do I have to use revalidation in this case?

[chrisburr]

@fkromer I think the suggestion is something like

schema_var_a = Map(...)
schema_var_b = Map(...)

config = load(my_yaml, MapPattern(Str(), Any()))

if "variant_a" in config:
    config = config.revalidate(schema_var_a)
elif "variant_b" in config:
    config = config.revalidate(schema_var_b)
else:
    raise ValueError(my_yaml)

config = config.data

The whole “Map({…}) | Map({…}) | Map({…})” approach I’m not really keen on since there’s no way to know which one the user was necessarily intending to match, so what error should it display? If the 4th out of 6 would have matched were it not for a mis-spelled key, then showing the error message that it didn’t match the last map (current behavior) isn’t very useful.

I think I would expect the error to come from the OrValidator with something like: failed to find a valid schema for the value starting at....

Example:

In my case the schema could be one of these three:

1. Currently possible solution

schema = MapPattern(Str(), Map({
    "name": Str(),
    "input": Map(Str(), Any()),
}))
data = load(my_yaml, schema)

for job_name, job_data in data.items():
    if "url" in job_data["input"]:
        job_data["input"].revalidate(Map({
            "url": Str(),
        }))
    elif "id" in job_data["input"]:
        job_data["input"].revalidate(Map({
            "id": Int(),
        }))
    elif "job" in job_data["input"]:
        job_data["input"].revalidate(Map({
            "job": Regex("(" + "|".join(map(re.escape, data.data.keys())),
        }))
    else:
        raise ValueError(f"No valid input type found for {job_name}")

2. Using an OrValidator with Map

data = load(my_yaml, MapPattern(Str(): Any()))

input_data_schema = Map({
    "url": Str(),
}) | Map({
    "id": Int(),
}) | Map({
    "job": Regex("(" + "|".join(map(re.escape, data.data.keys())),
})
full_schema = MapPattern(Str(), Map({
    "name": Str(),
    "input": input_data_schema,
}))
data.revalidate(full_schema)

3. After writing the first two I realised this could also be done using a custom validator class

I started writing a custom validator here but deleted it as it become quite long to do correctly for both validate and to_yaml.

Summary thoughts

I still prefer option (2). I can easily imagine option (1) becoming much more complicated if input_data_schema could appear in more places or at multiple levels in a deeper structure. If there are problems with (2) then (3) is an acceptable fallback.

[chrisburr]

Thanks @crdoconnor, it happens to us all 😆 (btw I’m loving strictyaml)

@fkromer Beautiful! 😉 Unfortunately mines a little messier as the map is the key of another map:

first_thing:
    input:
        url: http://example.com  # Str()

second_thing:
    input:
        id: 1234  # Int()

third_thing:
    input:
        job: first_thing  # Str() corresponding to one of the other top-level keys

I can workaround it by setting input to be a Map() and then looping over the keys to check which key exists so I can revalidate with the corresponding schema but it feels overly complicated.