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, 38 insertions, 6 deletions

diff --git a/src/text/template/parse/parse.go b/src/text/template/parse/parse.go
index a91a544ce0..ad9c051978 100644
--- a/src/text/template/parse/parse.go
+++ b/src/text/template/parse/parse.go
@@ -23,12 +23,13 @@ type Tree struct {
 	Root      *ListNode // top-level root of the tree.
 	text      string    // text parsed to create the template (or its parent)
 	// Parsing only; cleared after parse.
-	funcs     []map[string]interface{}
-	lex       *lexer
-	token     [3]item // three-token lookahead for parser.
-	peekCount int
-	vars      []string // variables defined at the moment.
-	treeSet   map[string]*Tree
+	funcs      []map[string]interface{}
+	lex        *lexer
+	token      [3]item // three-token lookahead for parser.
+	peekCount  int
+	vars       []string // variables defined at the moment.
+	treeSet    map[string]*Tree
+	rangeDepth int // nesting level of range loops.
 }
 
 // Copy returns a copy of the Tree. Any parsing state is discarded.
@@ -219,6 +220,7 @@ func (t *Tree) stopParse() {
 	t.vars = nil
 	t.funcs = nil
 	t.treeSet = nil
+	t.rangeDepth = 0
 }
 
 // Parse parses the template definition string to construct a representation of
@@ -373,6 +375,10 @@ func (t *Tree) action() (n Node) {
 		return t.templateControl()
 	case itemWith:
 		return t.withControl()
+	case itemBreak:
+		return t.breakControl()
+	case itemContinue:
+		return t.continueControl()
 	}
 	t.backup()
 	token := t.peek()
@@ -453,7 +459,13 @@ func (t *Tree) parseControl(allowElseIf bool, context string) (pos Pos, line int
 	defer t.popVars(len(t.vars))
 	pipe = t.pipeline(context)
 	var next Node
+	if context == "range" {
+		t.rangeDepth++
+	}
 	list, next = t.itemList()
+	if context == "range" {
+		t.rangeDepth--
+	}
 	switch next.Type() {
 	case nodeEnd: //done
 	case nodeElse:
@@ -498,6 +510,26 @@ func (t *Tree) rangeControl() Node {
 	return t.newRange(t.parseControl(false, "range"))
 }
 
+// Break:
+//	{{break}}
+// Break keyword is past.
+func (t *Tree) breakControl() Node {
+	if t.rangeDepth == 0 {
+		t.errorf("unexpected break outside of range")
+	}
+	return t.newBreak(t.expect(itemRightDelim, "break").pos)
+}
+
+// Continue:
+//	{{continue}}
+// Continue keyword is past.
+func (t *Tree) continueControl() Node {
+	if t.rangeDepth == 0 {
+		t.errorf("unexpected continue outside of range")
+	}
+	return t.newContinue(t.expect(itemRightDelim, "continue").pos)
+}
+
 // With:
 //	{{with pipeline}} itemList {{end}}
 //	{{with pipeline}} itemList {{else}} itemList {{end}}