ifchanged-tag added.

README.md

@@ -21,14 +21,14 @@ Please use the [issue tracker](https://github.com/flosch/pongo2/issues) if you'r
 
 Please also have a look on the [caveats](https://github.com/flosch/pongo2#caveats) and on the [official add-ons](https://github.com/flosch/pongo2#official).
 
-## New in pongo2
+## Features (and new in pongo2)
 
  * Entirely rewritten from the ground-up.
- * [Easy API to create new filters and tags](http://godoc.org/github.com/flosch/pongo2#RegisterFilter) ([including parsing arguments](http://godoc.org/github.com/flosch/pongo2#Parser)); take a look on an example and the differences between pongo1 and pongo2: [old](https://github.com/flosch/pongo/blob/master/filters.go#L65) and [new](https://github.com/flosch/pongo2/blob/master/filters_builtin.go#L72).
  * [Advanced C-like expressions](https://github.com/flosch/pongo2/blob/master/template_tests/expressions.tpl).
  * [Complex function calls within expressions](https://github.com/flosch/pongo2/blob/master/template_tests/function_calls_wrapper.tpl).
- * Additional features
-   * Macros (see [template_tests/macro.tpl](https://github.com/flosch/pongo2/blob/master/template_tests/macro.tpl))
+ * [Easy API to create new filters and tags](http://godoc.org/github.com/flosch/pongo2#RegisterFilter) ([including parsing arguments](http://godoc.org/github.com/flosch/pongo2#Parser))
+ * Additional features:
+    * Macros (see [template_tests/macro.tpl](https://github.com/flosch/pongo2/blob/master/template_tests/macro.tpl))
 
 ## Recent API changes within pongo2
 

pongo2_template_test.go

@@ -142,6 +142,32 @@ Yep!`,
 				Text: "<b>hello!</b> there",
 			},
 		},
+		"comments2": []*comment{
+			&comment{
+				Author: &user{
+					Name:      "user1",
+					Validated: true,
+				},
+				Date: time2,
+				Text: "\"pongo2 is nice!\"",
+			},
+			&comment{
+				Author: &user{
+					Name:      "user1",
+					Validated: true,
+				},
+				Date: time1,
+				Text: "comment2 with <script>unsafe</script> tags in it",
+			},
+			&comment{
+				Author: &user{
+					Name:      "user3",
+					Validated: false,
+				},
+				Date: time1,
+				Text: "<b>hello!</b> there",
+			},
+		},
 	},
 }
 

tags_ifchanged.go

@@ -0,0 +1,117 @@
+package pongo2
+
+import (
+	"bytes"
+)
+
+type tagIfchangedNode struct {
+	watched_expr []INodeEvaluator
+	last_values  []*Value
+	last_content []byte
+	thenWrapper  *NodeWrapper
+	elseWrapper  *NodeWrapper
+}
+
+func (node *tagIfchangedNode) Execute(ctx *ExecutionContext, buffer *bytes.Buffer) error {
+
+	if len(node.watched_expr) == 0 {
+		// Check against own rendered body
+
+		buf := bytes.NewBuffer(make([]byte, 0, 1024)) // 1 KiB
+		err := node.thenWrapper.Execute(ctx, buf)
+		if err != nil {
+			return err
+		}
+
+		buf_bytes := buf.Bytes()
+		if !bytes.Equal(node.last_content, buf_bytes) {
+			// Rendered content changed, output it
+			buffer.Write(buf_bytes)
+			node.last_content = buf_bytes
+		}
+	} else {
+		now_values := make([]*Value, 0, len(node.watched_expr))
+		for _, expr := range node.watched_expr {
+			val, err := expr.Evaluate(ctx)
+			if err != nil {
+				return err
+			}
+			now_values = append(now_values, val)
+		}
+
+		// Compare old to new values now
+		changed := len(node.last_values) == 0
+
+		for idx, old_val := range node.last_values {
+			if !old_val.EqualValueTo(now_values[idx]) {
+				changed = true
+				break // we can stop here because ONE value changed
+			}
+		}
+
+		node.last_values = now_values
+
+		if changed {
+			// Render thenWrapper
+			err := node.thenWrapper.Execute(ctx, buffer)
+			if err != nil {
+				return err
+			}
+		} else {
+			// Render elseWrapper
+			err := node.elseWrapper.Execute(ctx, buffer)
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	return nil
+}
+
+func tagIfchangedParser(doc *Parser, start *Token, arguments *Parser) (INodeTag, error) {
+	ifchanged_node := &tagIfchangedNode{}
+
+	for arguments.Remaining() > 0 {
+		// Parse condition
+		expr, err := arguments.ParseExpression()
+		if err != nil {
+			return nil, err
+		}
+		ifchanged_node.watched_expr = append(ifchanged_node.watched_expr, expr)
+	}
+
+	if arguments.Remaining() > 0 {
+		return nil, arguments.Error("Ifchanged-arguments are malformed.", nil)
+	}
+
+	// Wrap then/else-blocks
+	wrapper, endargs, err := doc.WrapUntilTag("else", "endifchanged")
+	if err != nil {
+		return nil, err
+	}
+	ifchanged_node.thenWrapper = wrapper
+
+	if endargs.Count() > 0 {
+		return nil, endargs.Error("Arguments not allowed here.", nil)
+	}
+
+	if wrapper.Endtag == "else" {
+		// if there's an else in the if-statement, we need the else-Block as well
+		wrapper, endargs, err = doc.WrapUntilTag("endifchanged")
+		if err != nil {
+			return nil, err
+		}
+		ifchanged_node.elseWrapper = wrapper
+
+		if endargs.Count() > 0 {
+			return nil, endargs.Error("Arguments not allowed here.", nil)
+		}
+	}
+
+	return ifchanged_node, nil
+}
+
+func init() {
+	RegisterTag("ifchanged", tagIfchangedParser)
+}

tags_spaceless.go

@@ -6,7 +6,7 @@ import (
 )
 
 type tagSpacelessNode struct {
-	wrapper    *NodeWrapper
+	wrapper *NodeWrapper
 }
 
 var tagSpacelessRegexp = regexp.MustCompile(`(?U:(<.*>))([\t\n\v\f\r ]+)(?U:(<.*>))`)

template_tests/ifchanged.tpl

@@ -0,0 +1,9 @@
+{% for comment in complex.comments2 %}
+    {% ifchanged %}New comment from another user {{ comment.Author.Name }}{% endifchanged %}
+    {% ifchanged comment.Author.Validated %}
+        Validated changed to {{ comment.Author.Validated }}
+    {% else %}
+        Validated value not changed
+    {% endifchanged %}
+    {% ifchanged comment.Author.Name comment.Date %}Comment's author name or date changed{% endifchanged %}
+{% endfor %}

template_tests/ifchanged.tpl.out

@@ -0,0 +1,18 @@
+
+    New comment from another user user1
+
+        Validated changed to True
+
+    Comment's author name or date changed
+
+
+
+        Validated value not changed
+
+    Comment's author name or date changed
+
+    New comment from another user user3
+
+        Validated changed to False
+
+    Comment's author name or date changed