Docs for 11ty/eleventy#879

src/docs/data-configuration.md

@@ -17,6 +17,7 @@ There are a few special data keys you can assign in your data to control how tem
 - `templateEngineOverride`: Override the template engine on a per-file basis. [Read more about Changing a Template’s Rendering Engine](/docs/languages/#overriding-the-template-language). [_This option only works in Front Matter ⚠️ (for now), read Issue #445_](https://github.com/11ty/eleventy/issues/445).
 - `eleventyExcludeFromCollections`: {% addedin "0.8.0" %} Set to `true` to exclude this content from any and all [Collections](/docs/collections/) (those tagged in data or setup using the Configuration API).
 - `eleventyComputed`: {% addedin "0.11.0" %} Programmatically set data values based on other values in your data cascade. Read more about [Computed Data](/docs/data-computed/).
+- `eleventyDataSchema`: Used to [validate data](/docs/data-validate/) in the data cascade.
 - `eleventyNavigation`: Used by the [Navigation plugin](/docs/plugins/navigation/#adding-templates-to-the-navigation).
 
 ## Advanced

src/docs/data-validate.md

@@ -0,0 +1,34 @@
+---
+eleventyNavigation:
+  parent: Data Cascade
+  key: Validate Data
+  order: 6
+---
+# Validate Data
+
+Use the special `eleventyDataSchema` data property to validate data in your Data Cascade. You can set this anywhere in your Data Cascade (front matter, directory data file, global data, etc).
+
+You can use any schema or validation library to achieve this. In this example, we’re using [`zod`](https://zod.dev/).
+
+## Example: Checking that `draft` is boolean
+
+In the following example, each content template with an `eleventyDataSchema` callback (in this example, any templates in the `blog` folder) is checked to make sure the value of any `draft` assignments must be `boolean` or `undefined`. If not, we throw an error.
+
+<div class="codetitle">blog/blog.11tydata.js</div>
+
+```js
+import { z } from "zod";
+import { fromZodError } from 'zod-validation-error';
+
+export default {
+	eleventyDataSchema: function(data) {
+		let result = z.object({
+			draft: z.boolean().or(z.undefined()),
+		}).safeParse(data);
+
+		if(result.error) {
+			throw fromZodError(result.error);
+		}
+	}
+};
+```