Changelog

Unreleased

Lists now collect all element errors instead of stopping at the first one, consistent with maps and tuples.
:integer, :float, :boolean, and :atom now treat empty strings as nil, like :string and the date/time types already did. This makes nilable and default work for these types when the input is "", and changes the error reason from :invalid_format to :unexpected_nil when neither option is set.

:atom no longer accepts an empty string as the atom :"". Since :"" always exists at runtime, String.to_existing_atom("") never raised and the empty value passed validation silently.
Optional fields and fields with defaults no longer hide :unexpected_type errors caused by malformed intermediate values in a source path. Only missing path segments trigger omission or a default.
Errors returned by nested union variants now preserve the full outer trace.

Custom function types now document that a bare capture such as &Version.parse/1 raises on input of an unexpected shape, and show the guard clause that returns {:error, :unexpected_type} instead.
Documented empty-string handling, the full validate return contract, and that defaults are final values which skip parsing and the shared option pipeline.
Completed the error-formatting example for all built-in reasons and corrected the nested trace example in the README.

source option for :union, :list, and :tuple types.
validate functions can now return :ok, :error, or {:error, reason} in addition to true/false. {:error, reason} allows custom error reasons; :ok/:error mirror true/false.

Dynamic maps (keys/values) now collect all entry errors instead of stopping at the first one, consistent with how fields behave.

New guide: using Mold with HTTP clients.
New guide: formatting errors.
Trace examples in README and parse!/2 docstring now use atoms instead of strings.

Error trace now uses schema field names (atoms like [:address, :city]) instead of raw source keys (strings like ["address", "city"]) or opaque Access function references ([#Function<...>]).
Dynamic map trace: key parse errors no longer include the unparsed key in the trace; value errors use the parsed key.

nilable: true combined with default no longer replaces an explicit nil with the default value. The default now only applies to missing fields.
Documentation updated to reflect the corrected nilable + default interaction.

Initial release.

Mold.parse/2 and Mold.parse!/2.
Built-in types: :string, :integer, :float, :boolean, :atom, :date, :datetime, :naive_datetime, :time.
Collections: :map (fields and homogeneous), :list, :tuple.
Union types, custom parse functions, recursive types.
Shared options: nilable, default, in, transform, validate.
Source key mapping with propagation to nested structures.
Rich error traces with path to the failing value.