v0.17 release 
Hi everyone!
This release brings discriminated unions, better control over unrecognized keys, deprecation support, metadata for format types and improvement on typespecs for structs.
Discriminated Union
A new type for creating discriminated unions based on a key field:
cat_schema = Zoi.map(%{type: Zoi.literal("cat"), meow: Zoi.string()})
dog_schema = Zoi.map(%{type: Zoi.literal("dog"), bark: Zoi.string()})
schema = Zoi.discriminated_union(:type, [cat_schema, dog_schema])
Zoi.parse(schema, %{type: "cat", meow: "meow!"})
{:ok, %{type: "cat", meow: "meow!"}}
New unrecognized keys option
Zoi.map/2, Zoi.object/2, Zoi.keyword/2, and Zoi.struct/3 now support an unrecognized_keys option to control how unknown keys are handled:
# Returns an error when unrecognized keys are present (replaces strict: true)
Zoi.map(%{name: Zoi.string()}, unrecognized_keys: :error)
# Preserves unrecognized keys without validation
Zoi.map(%{name: Zoi.string()}, unrecognized_keys: :preserve)
# Preserves unrecognized keys with validation
Zoi.map(%{name: Zoi.string()}, unrecognized_keys: {:preserve, {Zoi.string(), Zoi.any()}})
The strict option is now deprecated in favor of unrecognized_keys.
Deprecated option
All schema types now accept a deprecated option to emit deprecation warnings during parsing. Zoi.describe/1 and Zoi.to_json_schema/1 also reflect the deprecation:
schema = Zoi.map(%{
old_field: Zoi.string(deprecated: "use new_field instead"),
new_field: Zoi.string()
})
Zoi.parse(schema, %{old_field: "old", new_field: "new"})
# warning: :old_field is deprecated: use new_field instead
#=> {:ok, %{old_field: "old", new_field: "new"}}
Zoi.lazy/1 now supports MFA tuples
This enables lazy schemas to be stored in module attributes and used at compile time:
@schema Zoi.lazy({MyModule, :user_schema, []})
Format types now support metadata
Zoi.email/1, Zoi.url/1, Zoi.uuid/1, Zoi.ipv4/1, Zoi.ipv6/1, and Zoi.hex/1 now forward description, example, metadata and deprecated options:
schema = Zoi.url(description: "A URL", example: "https://example.com")
Zoi.description(schema) #=> "A URL"
Zoi.example(schema) #=> "https://example.com"
Improvement on typespecs for structs
Zoi.type_spec/1 for Zoi.struct/3 now resolves optional fields as nil. Zoi.default/3 with a nil value also resolves as nil:
schema = Zoi.struct(User, %{
name: Zoi.string(),
age: Zoi.optional(Zoi.integer())
})
# Generates: %User{name: binary(), age: nil | integer()}
Zoi.type_spec(schema)
Docs: hexdocs.pm/zoi
Hex: hex.pm/packages/zoi
Repo: github.com/phcurado/zoi
and congrats!
