Don't escape block strings (google#98)

* Don't escape block strings

Author: sbarzowski

ast/ast.go

@@ -416,6 +416,16 @@ const (
 	VerbatimStringSingle
 )
 
+func (k LiteralStringKind) FullyEscaped() bool {
+	switch k {
+	case StringSingle, StringDouble:
+		return true
+	case StringBlock, VerbatimStringDouble, VerbatimStringSingle:
+		return false
+	}
+	panic(fmt.Sprintf("Unknown string kind: %v", k))
+}
+
 // LiteralString represents a JSON string
 type LiteralString struct {
 	NodeBase

desugarer.go

@@ -502,15 +502,15 @@ func desugar(astPtr *ast.Node, objLevel int) (err error) {
 		// Nothing to do.
 
 	case *ast.LiteralString:
-		if node.Kind != ast.VerbatimStringDouble && node.Kind != ast.VerbatimStringSingle {
+		if node.Kind.FullyEscaped() {
 			unescaped, err := stringUnescape(node.Loc(), node.Value)
 			if err != nil {
 				return err
 			}
 			node.Value = unescaped
-			node.Kind = ast.StringDouble
-			node.BlockIndent = ""
 		}
+		node.Kind = ast.StringDouble
+		node.BlockIndent = ""
 	case *ast.Object:
 		// Hidden variable to allow $ binding.
 		if objLevel == 0 {

testdata/block_escaping.golden

@@ -0,0 +1 @@
+"\\n\n\\t\n"

testdata/block_escaping.jsonnet

@@ -0,0 +1,4 @@
+|||
+	\n
+	\t
+|||