# collectMergeKeyDiagnostics (/docs/api/functions/collectMergeKeyDiagnostics)



```ts
function collectMergeKeyDiagnostics(ctx): Diagnostic[];
```

Defined in: [packages/core/src/strict.ts:38](https://github.com/austenstone/actio/blob/2b01e694a0f76521d8c073f3c6a2e48917d2c9d9/packages/core/src/strict.ts#L38)

Flag YAML 1.1 merge keys (`<<`) in `.actio.yml` source for repos enforcing a
strict YAML 1.2.2 style. Lint-only: Actio still resolves and erases `<<` at
parse, so emitted YAML is byte-identical whether or not strict mode is on.
Anchors and aliases (`&`/`*`) are valid 1.2.2 core and are never flagged.

## Parameters [#parameters]

### ctx [#ctx]

[`ParseContext`](../interfaces/ParseContext.mdx)

## Returns [#returns]

[`Diagnostic`](../interfaces/Diagnostic.mdx)\[]


## Sitemap

Browse the full documentation: [Markdown sitemap](https://austenstone.github.io/actio/sitemap.md) · [XML sitemap](https://austenstone.github.io/actio/sitemap.xml)