Exported server routes returning binary files get corrupted

[aloker]

Describe the bug
When a route points to a server route that emits a binary file (pdf, image etc.) and the site is exported, the files on disk get corrupted because export only supports text results from server routes.

To Reproduce

• Create a server route that returns a binary file (image, PDF)
• Link to the server route inside a Svelte component
• Export the site
• Find the exported file of the server route on disk

Result: the file is corrupt and cannot be opened.

Expected behavior
The result of server routes emitting binary data should be properly stored on disk when exporting.

Information about your Sapper Installation:

• Sapper master branch (v0.27.10)
• Exported site
• Checked with rollup, but should be same for webpack

Severity
Blocking my attempt to load all data including binary assets (documents, images) from a headless CMS.

[swyxio]

this seems pretty serious. can you move the work to clientside? or must it be in a server route?

[aloker]

In the API routes, I pull in images from a CMS and transform them using Sharp, so yes, it has to be server side.

[jrob-io]

I ran into this issue, too. I realized that this.fetch uses proc.send to send the response body in a JSON object to the export CLI.

sapper/runtime/src/server/middleware/get_server_route_handler.ts

Line 40 in 5e2c686

body: Buffer.concat(chunks).toString()

JSON is utf8 which results in binary data being lost, so I base64 encoded it before and after the message was sent. After this, binary files started appearing normally in my __sapper__/export folder.

[dennybritz]

Is there any news on this getting fixed? It seems like I cannot export binary files and this is blocking me.