One form's declared rules, executed as a schemaless Ecto.Changeset.

What a rule is

A rule is one of the HTML constraint attributes already on the field node, lifted at compile time by MishkaCmsCore.Runtime.PageBuilder.PageForms into the field's :rules list. There is no second place to declare one, so the browser and the server enforce the same sentence:

:required                 required
{:min_length, n}          minlength="n"
{:max_length, n}          maxlength="n"
{:min, n}                 min="n"
{:max, n}                 max="n"
{:pattern, source}        pattern="source"
{:format, :email}         data-format="email"
{:format, :url}           data-format="url"
{:confirms, "password"}   data-confirms="password"

A rule this module does not know is ignored rather than raised on, because a template compiled by a newer editor must still run on an older node.

pattern is read the way HTML reads it: the whole value has to match, not some piece of it, so pattern="[0-9]{5}" refuses abcd12345xyz on both sides of the wire.

The shapes callers depend on

changeset/2 answers an Ecto.Changeset over {%{}, types}, so every error is {message, opts} — the only shape a kit's translate_error/1 matches — with Ecto's own opts[:count] and opts[:number] where Gettext's plural rules can read them.

The changeset keeps the WHOLE params map, including the _unused_<field> markers the client sends, which is what lets Phoenix.Component.used_input?/1 work over a form built from it.

apply_changes/2 answers a plain map of the cast values, keyed by atom, for whoever receives the submission.

Nothing here raises on what a visitor typed

A visitor can post a list where a string is expected, a word where a number is expected, or a date that is not one. Each of those is a validation error and never an exception, so a keystroke can never take a published page down. Where a stock Ecto validator would raise on such a value — validate_number/3 on a word, validate_format/4 on an integer — the value is read first and the validator is only reached with what it accepts.

See MishkaCmsCore.Runtime.PageForm for the runtime that builds the form and handles the events.