Add the ability to ignore errors in ExprTags

README.md

@@ -26,6 +26,7 @@ Salix's syntax is similar to Leaf and (in my opinion at least), it's much more f
   - [Global Functions](#global-functions)
   - [Adding Custom Functions](#adding-custom-functions)
 - [Expressions](#expressions)
+  - [Ignoring errors](#ignoring-errors)
   - [Ternary Expressions](#ternary-expressions)
   - [Coalescing operator](#coalescing-operator)
   - [The `in` operator](#the-in-operator)
@@ -189,6 +190,19 @@ You can include custom functions as variables using the WithVarMap method on tem
 
 Salix's expressions mostly work like Go's, but there are some extra features worth mentioning.
 
+### Ignoring errors
+
+If you'd like to ignore errors in an expression tag, you can do that by adding a question mark at the end.
+
+
+```html
+<!-- This would return an error if example wasn't defined or if it didn't have an Example() method -->
+#(example.Example())
+
+<!-- This would ignore any error and keep executing the rest of the template -->
+#(example.Example())?
+```
+
 ### Ternary Expressions
 
 Salix supports ternary expressions, which allow you to choose a value based on whether a condition is true. For example:

ast/ast.go

@@ -33,6 +33,7 @@ func (t Tag) Pos() Position {
 
 type ExprTag struct {
 	Value       Node
+	IgnoreError bool
 	Position    Position
 }
 

parser/salix.peg

@@ -59,7 +59,7 @@ Root = items:(Tag / ExprTag / EndTag / Text)* {
     return out, nil
 }
 
-Tag = '#' name:Ident params:ParamList? body:':'? {
+Tag = '#' name:Ident params:ParamList? ignoreErr:'?'? body:':'? {
     return ast.Tag{
         Name:        name.(ast.Ident),
         Params:      toNodeSlice(params),
@@ -75,9 +75,10 @@ EndTag = "#!" name:Ident {
     }, nil
 }
 
-ExprTag = "#(" item:Expr ')' {
+ExprTag = "#(" item:Expr ')' ignoreErr:'?'? {
     return ast.ExprTag{
         Value:       item.(ast.Node),
+        IgnoreError: ignoreErr != nil,
         Position:    getPos(c),
     }, nil
 }

salix.go

@@ -112,8 +112,12 @@ func (t *Template) execute(w io.Writer, nodes []ast.Node, local map[string]any)
 		case ast.ExprTag:
 			v, err := t.getValue(node.Value, local)
 			if err != nil {
+				if node.IgnoreError {
+					continue
+				} else {
 					return err
 				}
+			}
 			if _, ok := v.(ast.Assignment); ok {
 				continue
 			}