text/template: add break, continue actions in ranges

Adds the two range control actions "break" and "continue". They act the
same as the Go keywords break and continue, but are simplified in that
only the innermost range statement can be broken out of or continued.

Fixes #20531

Change-Id: I4412b3bbfd4dadb0ab74ae718e308c1ac7a0a1e9
Reviewed-on: https://go-review.googlesource.com/66410
Reviewed-by: Rob Pike <r@golang.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/src/text/template/parse/node.go b/src/text/template/parse/node.go
index 55ff46c17a..7e16349b31 100644
--- a/src/text/template/parse/node.go
+++ b/src/text/template/parse/node.go
@@ -69,6 +69,8 @@ const (
 	NodeTemplate                   // A template invocation action.
 	NodeVariable                   // A $ variable.
 	NodeWith                       // A with action.
+	NodeBreak                      // A break action.
+	NodeContinue                   // A continue action.
 )
 
 // Nodes.
@@ -796,6 +798,68 @@ func (r *RangeNode) Copy() Node {
 	return r.tr.newRange(r.Pos, r.Line, r.Pipe.CopyPipe(), r.List.CopyList(), r.ElseList.CopyList())
 }
 
+// BreakNode represents a {{break}} action.
+type BreakNode struct {
+	NodeType
+	Pos
+	tr *Tree
+}
+
+func (t *Tree) newBreak(pos Pos) *BreakNode {
+	return &BreakNode{NodeType: NodeBreak, Pos: pos, tr: t}
+}
+
+func (b *BreakNode) Type() NodeType {
+	return b.NodeType
+}
+
+func (b *BreakNode) String() string {
+	return "{{break}}"
+}
+
+func (b *BreakNode) Copy() Node {
+	return b.tr.newBreak(b.Pos)
+}
+
+func (b *BreakNode) Position() Pos {
+	return b.Pos
+}
+
+func (b *BreakNode) tree() *Tree {
+	return b.tr
+}
+
+// ContinueNode represents a {{continue}} action.
+type ContinueNode struct {
+	NodeType
+	Pos
+	tr *Tree
+}
+
+func (t *Tree) newContinue(pos Pos) *ContinueNode {
+	return &ContinueNode{NodeType: NodeContinue, Pos: pos, tr: t}
+}
+
+func (c *ContinueNode) Type() NodeType {
+	return c.NodeType
+}
+
+func (c *ContinueNode) String() string {
+	return "{{continue}}"
+}
+
+func (c *ContinueNode) Copy() Node {
+	return c.tr.newContinue(c.Pos)
+}
+
+func (c *ContinueNode) Position() Pos {
+	return c.Pos
+}
+
+func (c *ContinueNode) tree() *Tree {
+	return c.tr
+}
+
 // WithNode represents a {{with}} action and its commands.
 type WithNode struct {
 	BranchNode