Feature Request: Support Square Bracket Notation in Multipart Form Data

[coderabbitai]

Description

Currently, Fiber supports square bracket notation in form data when using 'application/x-www-form-urlencoded' content type, but this feature is not available for multipart form data. This limits the ability to handle complex nested data structures in multipart form requests.

Current Behavior

• Square bracket notation works with 'application/x-www-form-urlencoded'
• Multipart form data does not support square bracket notation for nested structures
• No support for comma-separated values in multipart form data

Desired Behavior

• Support square bracket notation in multipart form data (e.g., field[0][name], field[1][name])
• Support comma-separated values in multipart form data fields
• Maintain the ability to transfer binary data alongside structured form data

Use Case Example

text_prompts[0][text]: "A beautiful sunset over the ocean"
text_prompts[0][weight]: 0.7
text_prompts[1][text]: "mountain range covered in snow"
text_prompts[1][weight]: -0.5
init_image: <binary_data>

References

• Original Issue: 🤗 [Question]: bodyParser nested with bracket notation #3223
• Current Implementation (form-urlencoded):

  fiber/ctx.go

  Lines 394 to 408 in 8c84b0f

  	if strings.HasPrefix(ctype, MIMEApplicationForm) {
  	data := make(map[string][]string)
  	var err error
  	c.fasthttp.PostArgs().VisitAll(func(key, val []byte) {
  	if err != nil {
  	return
  	}
  	k := c.app.getString(key)
  	v := c.app.getString(val)
  	if strings.Contains(k, "[") {
  	k, err = parseParamSquareBrackets(k)
  	}

• Current Implementation (multipart):

  fiber/ctx.go

  Lines 422 to 427 in 8c84b0f

  	if strings.HasPrefix(ctype, MIMEMultipartForm) {
  	data, err := c.fasthttp.MultipartForm()
  	if err != nil {
  	return err
  	}
  	return c.parseToStruct(bodyTag, out, data.Value)

Additional Notes

This enhancement would provide consistency between form-urlencoded and multipart form data handling, making it easier for developers to work with complex data structures while maintaining the ability to upload files.