Missing keys, None, and defaults

Missing and None are different inputs

Optional(str) permits an absent key, which is omitted from the result. str | None accepts a present null value but still requires the key. Optional(str, 'Ada') inserts a default only when the key is absent.

from zodify import Optional, validate

assert validate({"name": Optional(str)}, {}) == {}
assert validate({"name": str | None}, {"name": None}) == {"name": None}
assert validate({"name": Optional(str, "Ada")}, {}) == {"name": "Ada"}
# Released 0.6.0 defaults are inserted as supplied, without validation or copying.
default = []
result = validate({"items": Optional([str], default)}, {})
assert result["items"] is default
assert validate({"count": Optional(int, "unchecked")}, {})["count"] == "unchecked"
try:
    validate({"name": str | None}, {})
except ValueError:
    pass  # Nullable still requires the key.
else:
    raise AssertionError("Expected missing-key failure")
print("optional-defaults: passed")

Defaults in the released version

In 0.6.0, a default is inserted as supplied. It is not independently validated or copied. Mutable defaults may be shared between calls. The executable example deliberately demonstrates an invalid default being inserted; this documents behavior, not a recommended configuration.

Prefer immutable, type-correct defaults and construct fresh mutable values in application code. A future default policy belongs to a separately released migration; do not assume unreleased source changes apply to an installed package.

• Roadmap →
• Schema containers →