When calling Render with a layout and a nil binding: panic: assignment to entry in nil map

[flowonyx]

The issue is that in jetVarMap it assumes that a nil binding should result in a nil jet.VarMap.

template/jet/jet.go

Lines 233 to 237 in c4b2c7e

	func jetVarMap(binding interface{}) jet.VarMap {
	var bind jet.VarMap
	if binding == nil {
	return bind
	}

But if a layout is specified, it is then used to set a function and panics:

template/jet/jet.go

Lines 219 to 229 in c4b2c7e

	bind := jetVarMap(binding)
	if len(layout) > 0 {
	lay, err := e.Templates.GetTemplate(layout[0])
	if err != nil {
	return err
	}
	bind.Set(e.layout, func() {
	_ = tmpl.Execute(out, bind, nil)
	})
	return lay.Execute(out, bind, nil)
	}

This could be solved either by replacing var bind jet.VarMap with bind := make(jet.VarMap) or by checking if bind is nil (and makeing it if not) in Render right after if len(layout) > 0 {.

// var bind jet.VarMap
bind := make(jet.VarMap)

Or in Render

bind := jetVarMap(binding) 
 if len(layout) > 0 { 
        if bind == nil {
                bind = make(jet.VarMap)
        }
 	lay, err := e.Templates.GetTemplate(layout[0]) 
 	if err != nil { 
 		return err 
 	} 
 	bind.Set(e.layout, func() { 
 		_ = tmpl.Execute(out, bind, nil) 
 	}) 
 	return lay.Execute(out, bind, nil) 
 } 

I would send a pull request, but I'm not sure if it matters to you which way it is fixed. I would think it would be much clearer to put it in jetVarMap and get rid of the other calls to make there, but I guess there was a reason to not do that in the first place.

---

The work around is for the caller of Render to just specify an empty jet.VarMap or fiber.Map but that is not obvious and panicing from forgetting is not great.

[justledbetter]

I've found another way this blows up:

When using gofiber/fiber/v3 on the upstream and using fiber.Ctx.Render to draw the page content using Jet templates, we're forced to pass in a v3 fiber.Map to the calling function, which fails the (type) switch in jetVarMap since fiber/v3.Map is not the same thing as the fiber/v2.Map that the case statement on line 205 expects:

	switch binds := binding.(type) {
	case map[string]interface{}:
		bind = make(jet.VarMap)
		for key, value := range binds {
			bind.Set(key, value)
		}
	case fiber.Map: // <-------------------- this is (fiber/v2).Map, but we're passing in (v3).Map
		bind = make(jet.VarMap)
		for key, value := range binds {
			bind.Set(key, value)
		}
	case jet.VarMap:
		bind = binds
	}

Is there any way to upgrade gofiber/template to work with gofiber/fiber/v3?

[justledbetter]

Found a way to get it to work (by adding an import to gofiber/fiber/v3 to template/jet/jet.go; The patch to jet.go looks like the following (happy to submit as a PR but holding off on doing that until I get your blessing that this is a desirable solution.... 😅)

--- a/jet/jet.go
+++ b/jet/jet.go
@@ -10,6 +10,7 @@ import (
        "strings"
 
        "github.com/gofiber/fiber/v2"
+       newfiber "github.com/gofiber/fiber/v3"
 
        "github.com/CloudyKit/jet/v6"
        "github.com/CloudyKit/jet/v6/loaders/httpfs"
@@ -207,6 +208,11 @@ func jetVarMap(binding interface{}) jet.VarMap {
                for key, value := range binds {
                        bind.Set(key, value)
                }
+       case newfiber.Map:
+               bind = make(jet.VarMap)
+               for key, value := range binds {
+                       bind.Set(key, value)
+               }
        case jet.VarMap:
                bind = binds
        }

[justledbetter]

(... Of course, upgrading the gofiber/template package to v3 may be in the works already; Happy to beta test if that's the right way to do it!)

[gaby]

I've found another way this blows up:

When using gofiber/fiber/v3 on the upstream and using fiber.Ctx.Render to draw the page content using Jet templates, we're forced to pass in a v3 fiber.Map to the calling function, which fails the (type) switch in jetVarMap since fiber/v3.Map is not the same thing as the fiber/v2.Map that the case statement on line 205 expects:

	switch binds := binding.(type) {
	case map[string]interface{}:
		bind = make(jet.VarMap)
		for key, value := range binds {
			bind.Set(key, value)
		}
	case fiber.Map: // <-------------------- this is (fiber/v2).Map, but we're passing in (v3).Map
		bind = make(jet.VarMap)
		for key, value := range binds {
			bind.Set(key, value)
		}
	case jet.VarMap:
		bind = binds
	}

Is there any way to upgrade gofiber/template to work with gofiber/fiber/v3?

Not yet, v3 is still under development. We are trying to merge as many improvements/fixes