There were a number of things wrong or could have been improved with the
[Draft Preview
Example](https://github.com/payloadcms/payload/tree/main/examples/draft-preview),
namely:
- The package.json was missing `"type": "modue"` which would throw ESM
related import errors on startup
- The preview secret was missing entirely, with pointless logic was
written to throw an error if it missing in the search params as opposed
to not matching the environment secret
- The `/next/exit-preview` route was duplicated twice
- The preview endpoint was unnecessarily querying the database for a
matching document as opposed to letting the underlying page itself 404
as needed, and it was also throwing an inaccurate error message
Some less critical changes were:
- The page query was missing the `depth` and `limit` parameters which is
best practice to optimize performance
- The logic to format search params in the preview URL was unnecessarily
complex
- Utilities like `generatePreviewPath` and `getGlobals` were
unnecessarily obfuscating simple functions
- The `/preview` and `/exit-preview` routes were unecessarily nested
within a `/next` page segment
- Payload types weren't aliased
Thoroughly documents the `admin.preview` feature. Previously, this
information was briefly mentioned in two distinct places, within the
collections config and again within the globals config. This led to
discrepancies over time and was inadequate at describing this feature,
such as having a lack of concrete code examples especially as it relates
to _draft preview_. There has also been confusion between this and Live
Preview.
Now, there is a dedicated page at `/admin/preview` which centralizes
this information into a single document. It also specifically documents
how to achieve _draft preview_ and includes code snippets. This way, we
no longer have to rely solely on the [Draft Preview
Example](https://github.com/payloadcms/payload/tree/main/examples/draft-preview)
for this.
Related: #10798
