Extending Onctuous

Folder structure

Onctuous
+-- onctuous            => the real code
|   +-- tests
|       +-- unit        => all individual validators and low level logic
|       `-- functional  => global behovior
+-- docs
    `-- pages           => what you are reading

Adding a custom validator

If you want to contribute to Onctuous (we would love it btw), you will need to add your custom validator into ddmock.validators module. Otherwise, put it wherever you want, there are no restrictions.

By convention, validators are:

• Callable
• Returns the validated value on success, even unmodified. This ensures chainability
• Raises Invalid on failure

All validators will look like this:

# Parent function: loads the parameters
def ValidatorName(param1, param2, msg=None):
    # this 'inner' function does the real job and is called by ``Onctuous``
    def f(v):
        if some condition:
            return v  # All changes done to the value will be reflected in the validated object
        raise Invalid(msg or 'Ooops: "Some Condition" was not met!')
    return f

For example, here is the Url validator:

def Url(msg=None):
    """Verify that the value is a URL."""
    def f(v):
        try:
            urlparse.urlparse(v)
            return v
        except:
            raise Invalid(msg or 'expected a URL')
    return f

That’s all you need to do!

Adding a custom marker

Sadly, this is quite more invasive to do and will probably require you to patch the heart of Onctuous.

Markers lives in the same module as Validators: ddmock.validators and are also callable.

The most simple Marker you can do is the “Optional” marker:

class Optional(Marker):
    """Mark a node in the schema as optional."""

But you could override __init__ or __call__ for instance.

Then, Marker presence is detected in Schema._validate_dict in module ddmock.schema, that is to say, the heart of Onctuous