exec tag added to enable treating evaluated string as a part of the t…

docs/tags.md

@@ -10,6 +10,7 @@ Implemented tags so far which needs documentation:
 * comment
 * cycle
 * extends
+* exec
 * filter
 * firstof
 * for

tags_exec.go

@@ -0,0 +1,44 @@
+package pongo2
+
+import (
+	"bytes"
+)
+
+type tagExecNode struct {
+	position    *Token
+	bodyWrapper *NodeWrapper
+}
+
+func (node *tagExecNode) Execute(ctx *ExecutionContext, writer TemplateWriter) *Error {
+	temp := bytes.NewBuffer(make([]byte, 0, 1024)) // 1 KiB size
+
+	err := node.bodyWrapper.Execute(ctx, temp)
+	if err != nil {
+		return err
+	}
+	templateSet := ctx.template.set
+	currentTemplate, err2 := templateSet.FromBytes(temp.Bytes())
+	if err2 != nil {
+		return err2.(*Error)
+	}
+	currentTemplate.root.Execute(ctx, writer)
+	return nil
+}
+
+func tagExecuteParser(doc *Parser, start *Token, arguments *Parser) (INodeTag, *Error) {
+	execNode := &tagExecNode{
+		position: start,
+	}
+
+	wrapper, _, err := doc.WrapUntilTag("endexec")
+	if err != nil {
+		return nil, err
+	}
+	execNode.bodyWrapper = wrapper
+
+	return execNode, nil
+}
+
+func init() {
+	RegisterTag("exec", tagExecuteParser)
+}

template_tests/exec.helper

@@ -0,0 +1 @@
+{% macro m4(arg) export %}{{arg}}{% endmacro %}

template_tests/exec.tpl

@@ -0,0 +1,13 @@
+{% with val = "{{ simple.name }}" %}{% exec %}{{val}}{% endexec %}{% endwith %}
+
+{% exec %}{% macro m1() %}some text{% endmacro %}{% endexec %}{{m1()}}
+
+{% exec %}{% autoescape off %}{% macro m2(arg) export %}some text with {{arg}}{% endmacro %}{% endautoescape %}{% endexec %}{{m2("arg value")}}
+
+{% with val = "{% macro m3() export %}m3 text{% endmacro %}{{m3()}}" %}{% exec %}{{val}}{% endexec %}{% endwith %}
+
+{% with val = '{% import "template_tests/exec.helper" m4 %}' %}{% exec %}{% autoescape off %}{{val}}{% endautoescape %}{% endexec %}{{m4("arg value")}}{% endwith %}
+
+{% exec %}{% macro m1() export %}some text{% endmacro %}{% endexec %}{{m1()}}
+
+{% with chars = "abc"|make_list val = "{% for i in chars %}{{i}}{% endfor %}" %}{% exec %}{{val}}{% endexec %}{% endwith %}

template_tests/exec.tpl.out

@@ -0,0 +1,13 @@
+john doe
+
+some text
+
+some text with arg value
+
+m3 text
+
+arg value
+
+some text
+
+abc