Environment

• Server version: 7.1.7
• Node.js version: v25.2.1
• npm version: 11.6.2

Description

Non-RDF resources (e.g., .txt, .jpg, .pdf files) return an Accept-Patch header advertising support for RDF patch formats (text/n3, application/sparql-update), but when clients attempt to PATCH these resources with RDF data, they receive a 501 Not Implemented error stating "No conversion path could be made from text/plain to internal/quads".

Expected Behavior

When a client sends a PATCH request with RDF content (N3 Patch or SPARQL Update) to a non-RDF resource, the server should successfully apply the patch to the corresponding .meta file:

PATCH /document.txt HTTP/1.1
Content-Type: application/sparql-update

INSERT DATA { <#subject> <#predicate> "value" . }

HTTP/1.1 205 Reset Content

The patch should be applied to /document.txt.meta, allowing clients to add metadata to non-RDF resources using the resource URL directly.

Actual Behavior

The server returns a 501 error when attempting to PATCH a non-RDF resource with RDF data:

GET /document.txt HTTP/1.1

HTTP/1.1 200 OK
Content-Type: text/plain
Accept-Patch: text/n3, application/sparql-update

PATCH /document.txt HTTP/1.1
Content-Type: application/sparql-update

INSERT DATA { <#subject> <#predicate> "value" . }

HTTP/1.1 501 Not Implemented
Content-Type: application/json

{
  "name": "NotImplementedHttpError",
  "message": "No conversion path could be made from text/plain to internal/quads:1,internal/*:0.",
  "statusCode": 501,
  "errorCode": "H501",
  "details": {}
}

Steps to Reproduce

1. Start the Community Solid Server with default configuration
2. Create a non-RDF resource:

   curl -X PUT http://localhost:3000/test.txt \
     -H "Content-Type: text/plain" \
     -d "test content"

3. Verify it advertises Accept-Patch:

   curl -i http://localhost:3000/test.txt | grep -i accept-patch
   # Returns: Accept-Patch: text/n3, application/sparql-update

4. Try to PATCH with RDF data:

   curl -X PATCH http://localhost:3000/test.txt \
     -H "Content-Type: application/sparql-update" \
     -d "INSERT DATA { <#s> <#p> <#o> . }"

5. Observe the 501 error response:

   {
     "name": "NotImplementedHttpError",
     "message": "No conversion path could be made from text/plain to internal/quads:1,internal/*:0.",
     "statusCode": 501
   }

6. Verify that PATCHing the .meta file directly works:

   curl -X PATCH http://localhost:3000/test.txt.meta \
     -H "Content-Type: application/sparql-update" \
     -d "INSERT DATA { <#s> <#p> <#o> . }"
   # Returns: 205 Reset Content (success)

Impact

• Clients cannot use the Accept-Patch header to add metadata to non-RDF resources
• The advertised capability (Accept-Patch: text/n3, application/sparql-update) is misleading
• Clients must know to PATCH .meta files specifically, rather than using the resource URL