ModelService: Cannot add model because it already exists

[junteudjio]

Describe the Bug

When using Json field with a jsonSchema, it's currently impossible to add multiple items with the same JsonField URI in the admin panel.
For instance, if I have a ui-block (say featuresJsonBlock) containing a json field with a specific jsonSchema, I can only add ONE featuresJsonBlock on my page/post. If I try to add another featuresJsonBlock, monaco editor will throw an error similar to what's described here: atularen/ngx-monaco-editor#48 or microsoft/monaco-editor#926 .

I solved it on my end by creating a custom json field and edited the existing code in @payloadcms/ui/src/fields/JSON/index.tsx slightly.
But perhaps this could be added to payload/ui itself.

  const handleMount = useCallback(
    (editor, monaco) => {
      if (!jsonSchema) {
        return
      }

      const existingSchemas = monaco.languages.json.jsonDefaults.diagnosticsOptions.schemas || []
      // if the schema is already in the existingSchemas, don't add it again
      if (existingSchemas.some(schema => schema.uri === jsonSchema.uri)) {
        return
      }
      const modelUri = monaco.Uri.parse(jsonSchema.uri)

      const model = monaco.editor.createModel(JSON.stringify(value, null, 2), 'json', modelUri)
      monaco.languages.json.jsonDefaults.setDiagnosticsOptions({
        enableSchemaRequest: true,
        schemas: [...existingSchemas, jsonSchema],
        validate: true,
      })

      editor.setModel(model)
    },
    [jsonSchema, value],
  )

Link to the code that reproduces this issue

https://github.com/payloadcms/payload/blob/466f109152bc6bf9a67e7d7bafd38c7d57a881de/packages/ui/src/fields/JSON/index.tsx

Reproduction Steps

• create a block with a jsonField with a specific jsonSchema
• try to add that block more than once in a Page/Post
• monaco editor will throw the error below
  ModelService: Cannot add model because it already exists

Which area(s) are affected? (Select all that apply)

area: ui

Environment Info

Payload

[akhrarovsaid]

Hey @junteudjio,

While the solution you describe will indeed work, it is a little bit unsatisfactory because, as a result, it would prevent subsequent JSON fields from having schema validation applied to them. I'm honestly not too sure about this one. If you have multiple JSON fields, a workaround is to simply provide them different uri's/filenames to prevent this from happening. Although, that will not work in something like an Array field.