📝 [Proposal]: We need partial render!

[vmpartner]

Feature Proposal Description

We have amazing gofiber + htmx + sse. We can send partial template on each update via SSE
Example how it can be reached now:

app.Get("/", func (c fiber.Ctx) error {
  return c.SendStreamWriter(func(w *bufio.Writer) {
   for {
    data := getLiveData()
    buf := new(bytes.Buffer)
    c.App().Config().Views.Render(buf, "my-live-partial-template", data) // hack for partial render
    w.WriteString(buf)
    time.Sleep(5*time.Second)
   }
  })
})

I propose that we can add method RenderToWriter(w *bufio.Writer, templateName string, data fiber.Map, layoutName string)

app.Get("/", func (c fiber.Ctx) error {
  return c.SendStreamWriter(func(w *bufio.Writer) {
   for {
    data := getLiveData()
    c.RenderToWriter(w, "my-live-partial-template", data)
    time.Sleep(5*time.Second)
   }
  })
})

Alignment with Express API

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HTTP RFC Standards Compliance

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API Stability

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Feature Examples

app.Get("/", func (c fiber.Ctx) error {
  return c.SendStreamWriter(func(w *bufio.Writer) {
   for {
    data := getLiveData()
    c.RenderToWriter(w, "my-live-partial-template", data)
    time.Sleep(5*time.Second)
   }
  })
})

Checklist:

• I agree to follow Fiber's Code of Conduct.
• I have searched for existing issues that describe my proposal before opening this one.
• I understand that a proposal that does not meet these guidelines may be closed without explanation.

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[grivera64]

+1 This sounds like a great idea. Due to the way SSE and c.SendStreamWriter() works, this might require two separate endpoints to work but seems do-able. Do you have a full working example using c.SendStreamWriter() on hand?

A problem we could potentially have with this is that a fiber.Ctx isn't considered safe to use from inside of c.SendStreamWriter() (not sure if this is mentioned in the docs). Reading could potentially be fine, but writing will cause issues from my experience working on the SendStreamWriter feature. If we were to add this method to the fiber.Ctx interface, then it may give a false impression that other Ctx methods would work here too (including ones that write to the response).

If possible, we may want to add this functionality to a different interface to avoid that confusion.

[JIeJaitt]

@grivera64 @vmpartner Should we implement this functionality out as a new middleware?

[vmpartner]

I think method RenderToWriter must appear inside main app, it cannot be implement in middleware

[grivera64]

@grivera64 @vmpartner Should we implement this functionality out as a new middleware?

I think it is possible to use a middleware to encapsulate the feature, though we would still need to implement a RenderToXXX() function of some sort like @vmpartner said.

An idea could be to create this method under a separate package (or even bundle it alongside the middleware in a partials package) to either render the template:

• as a string/[]byte that can be sent over the network

partials.RenderAsBytes(templateName string) []byte

• into a *bufio.Writer so we can use it directly like in the above

partials.RenderToWriter(w *bufio.Writer, templateName string) error

This way, we could directly use this in a middleware:

app.Get("/partial", partials.New("my-partial", func() fiber.Map {
  return getLiveData() // assuming getLiveData() returns a bind of type fiber.Map
})

What do you both think about this setup? @vmpartner @JIeJaitt

[JIeJaitt]

@grivera64 Sounds good！