From bb9b6c812890e045b8f5796178a8f20bfb68cdd6 Mon Sep 17 00:00:00 2001
From: Elara6331 <elara@elara.ws>
Date: Wed, 20 Mar 2024 14:31:43 -0700
Subject: [PATCH] Add NilToZero option

---
 namespace.go | 11 +++++++++++
 salix.go     | 19 ++++++++++++++++++-
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/namespace.go b/namespace.go
index a26b255..4bed359 100644
--- a/namespace.go
+++ b/namespace.go
@@ -20,6 +20,9 @@ type Namespace struct {
 	// WriteOnSuccess indicates whether the output should only be written if generation fully succeeds.
 	// This option buffers the output of the template, so it will use more memory. (default: false)
 	WriteOnSuccess bool
+	// NilToZero indictes whether nil pointer values should be converted to zero values of their underlying
+	// types.
+	NilToZero bool
 	escapeHTML     *bool
 }
 
@@ -86,6 +89,14 @@ func (n *Namespace) WithWhitespaceMutations(b bool) *Namespace {
 	return n
 }
 
+// WithNilToZero enables or disables conversion of nil values to zero values for the namespace
+func (n *Namespace) WithNilToZero(b bool) *Namespace {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+	n.NilToZero = true
+	return n
+}
+
 // GetTemplate tries to get a template from the namespace's template map.
 // If it finds the template, it returns the template and true. If it
 // doesn't find it, it returns nil and false.
diff --git a/salix.go b/salix.go
index 9cde930..31213d3 100644
--- a/salix.go
+++ b/salix.go
@@ -26,6 +26,7 @@ type Template struct {
 	// WriteOnSuccess indicates whether the output should only be written if generation fully succeeds.
 	// This option buffers the output of the template, so it will use more memory. (default: false)
 	WriteOnSuccess bool
+	NilToZero bool
 
 	tags   map[string]Tag
 	vars   map[string]any
@@ -66,6 +67,12 @@ func (t Template) WithWriteOnSuccess(b bool) Template {
 	return t
 }
 
+// WithNilToZero enables or disables conversion of nil values to zero values.
+func (t Template) WithNilToZero(b bool) Template {
+	t.NilToZero = true
+	return t
+}
+
 // Execute executes a parsed template and writes
 // the result to w.
 func (t Template) Execute(w io.Writer) error {
@@ -147,6 +154,10 @@ func (t *Template) getEscapeHTML() bool {
 	}
 }
 
+func (t *Template) getNilToZero() bool {
+	return t.NilToZero || t.ns.NilToZero
+}
+
 func (t *Template) toString(v any) string {
 	if h, ok := v.(HTML); ok {
 		return string(h)
@@ -334,14 +345,20 @@ func (t *Template) unwrapASTValue(node ast.Value, local map[string]any) (any, er
 		return nil, err
 	}
 
+	rval := reflect.ValueOf(v)
+
 	if node.Not {
-		rval := reflect.ValueOf(v)
 		if rval.Kind() != reflect.Bool {
 			return nil, ast.PosError(node, "%s: the ! operator can only be used on boolean values", valueToString(node))
 		}
 		return !rval.Bool(), nil
 	}
 
+	if rval.Kind() == reflect.Pointer && rval.IsNil() && t.getNilToZero() {
+		rtyp := rval.Type().Elem()
+		return reflect.New(rtyp).Interface(), nil
+	}
+
 	return v, err
 }