Forms, context & pitfalls

Form error handling

Automatic display (via {% form.xxx %})

When using {% form.signup_form %}, validation errors are automatically rendered under each relevant field.

Manual display of global errors

{% if signup_form.errors %}
    <div class="alert alert-warning">
        <ul>
            {% for field_name, error_msg in signup_form.errors %}
                <li><strong>{{ field_name }}:</strong> {{ error_msg }}</li>
            {% endfor %}
        </ul>
    </div>
{% endif %}

// Rust handler
pub async fn signup(
    mut request: Request,
    Prisme(mut form): Prisme<RegisterForm>,
) -> AppResult<Response> {
    if request.is_get() {
        context_update!(request => {
            "title" => "Sign Up",
            "signup_form" => &form,
        });
        return request.render("signup.html");
    }

    if request.is_post() {
        if form.is_valid().await {
            let user = form.save(&request.engine.db).await.map_err(|err| {
                form.get_form_mut().database_error(&err);
                AppError::from(err)
            })?;
            success!(request.notices => format!("Welcome {}!", user.username));
            return Ok(Redirect::to("/").into_response());
        }

        context_update!(request => {
            "title" => "Validation Error",
            "signup_form" => &form,
            "messages" => flash_now!(error => "Please fix the errors"),
        });
        return request.render("signup.html");
    }

    request.render("signup.html")
}

{% extends "base.html" %}

{% block title %}{{ title }}{% endblock %}

{% block content %}
    <h1>{{ title }}</h1>
    {% messages %}
    <form method="post" action="/signup">
        {% form.signup_form %}
        <button type="submit" class="btn btn-primary">Sign up</button>
    </form>
{% endblock %}

When using {% form.user %}, the variable user must be a Prisme form:

// ❌ ERROR: "user" is a SeaORM Model, not a form
context_update!(request => {
    "user" => &db_user,  // the form filter will crash!
});

// ✅ CORRECT: separate form and DB entity
context_update!(request => {
    "user" => &form,           // form → {% form.user %} works
    "found_user" => &db_user,  // Model → {{ found_user.email }}
});