# AUR6001

## Error Message

`AUR6001: Invalid calculation state. Virtual repeater has no items.`

## Description

This error occurs when the virtual repeater tries to perform a measurement/render calculation that requires an items collection, but the collection is missing (null/undefined) or empty at a time when the strategy expects at least one item.

## Example Trigger

```ts
export class MyList {
  // ❌ items is undefined initially
  items: unknown[];
}
```

```html
<template>
  <div virtual-repeat.for="item of items">${item}</div>
</template>
```

## Correct Usage

* Initialize the collection (`items = []`) and then replace it when data arrives.
* If the list is conditional, guard it with `if.bind` until data is ready.

```ts
export class MyList {
  // ✅ always an array
  items: unknown[] = [];
}
```

```html
<template>
  <div if.bind="items.length">
    <div virtual-repeat.for="item of items">${item}</div>
  </div>
</template>
```

## Troubleshooting

* Verify the collection expression resolves to an `Array` (or a supported collection type for your setup).
* If the collection is async-loaded, ensure it’s initialized before the template is rendered.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.aurelia.io/developer-guides/error-messages/ui-virtualization/aur6001.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.