Validate templates

Status: Current. How-to guide for developers.

This guide shows how to check a template against the shape of its model before any data exists. Run the check where templates enter the application, when one is saved or uploaded, and in a test over every template the application ships, so that a typo is a failed check rather than a blank in a document.

Validate checks a template against the shape of its model, without rendering and without data: every path, attribute, block and document setting. It never throws for what the template says; it throws only when the bytes are not an OpenDocument text.

using Allors.Document.Reflection;

IShape model = ReflectionShape.Arguments<InvoiceModel>();
TemplateValidation validation = OpenDocumentTemplate.Validate(templateBytes, model);

if (!validation.IsValid)
{
    foreach (Finding finding in validation.Errors)
    {
        Console.WriteLine(finding); // error: <$Invoice.Totl>: Invoice has no member Totl (content.xml paragraph 12 "Total <$Invoice.Totl>")
    }
}

The shape is the root the template renders against. ReflectionShape.Arguments<T>() is what OpenDocumentTemplate<T> sees: the public properties of T by their exact names. ReflectionShape.Of<T>() is an object of T itself, for a model rendered through ReflectionResolver. For a dictionary model use DictionaryShape: DictionaryShape.Open accepts every member, new DictionaryShape(members) knows exactly which names exist and what their shapes are. IsValid is true when there are no errors. Inside an <@if> or <@ifdef> block the guarded path is narrowed to the shapes that have the member, for models whose shapes declare Variants; the else of an <@ifdef> sees the shapes without it, the else of an <@if> sees them all, not swaps the two, and an else with a test of its own narrows again.