handle escaped backslashes (#1997)

pkg/yqlib/operator_strings.go

@@ -54,40 +54,52 @@ func interpolate(d *dataTreeNavigator, context Context, str string) (string, err
 	for i := 0; i < len(runes); i++ {
 		char := runes[i]
 		if !inExpression {
-			if char == '\\' && i != len(runes)-1 && runes[i+1] == '(' {
+			if char == '\\' && i < len(runes)-1 {
+				switch runes[i+1] {
+				case '(':
 					inExpression = true
-				i = i + 1 // skip over the next open bracket
+					// skip the lparen
+					i++
 					continue
+				case '\\':
+					// skip the escaped backslash
+					i++
+				default:
+					log.Debugf("Ignoring non-escaping backslash @ %v[%d]", str, i)
+				}
 			}
 			sb.WriteRune(char)
 		} else { // we are in an expression
-			if char == ')' && nestedBracketsCounter == 0 {
+			if char == ')' {
+				if nestedBracketsCounter == 0 {
 					// finished the expression!
 					log.Debugf("Expression is :%v", expSb.String())
 					value, err := evaluate(d, context, expSb.String())
 					if err != nil {
 						return "", err
 					}
-
 					inExpression = false
 					expSb = strings.Builder{} // reset this
 
 					sb.WriteString(value)
 					continue
+				}
+				nestedBracketsCounter--
 			} else if char == '(' {
 				nestedBracketsCounter++
-			} else if char == '\\' && i != len(runes)-1 && runes[i+1] == ')' {
-				// close brackets is escaped, skip over it
-				expSb.WriteRune(char)
-				expSb.WriteRune(runes[i+1])
-				i = i + 1
+			} else if char == '\\' && i < len(runes)-1 {
+				switch esc := runes[i+1]; esc {
+				case ')', '\\':
+					// write escaped character
+					expSb.WriteRune(esc)
+					i++
 					continue
-			} else if char == ')' {
-				nestedBracketsCounter--
+				default:
+					log.Debugf("Ignoring non-escaping backslash @ %v[%d]", str, i)
+				}
 			}
 			expSb.WriteRune(char)
 		}
-
 	}
 	if inExpression {
 		return "", fmt.Errorf("unclosed interpolation string \\(")

pkg/yqlib/operator_strings_test.go

@@ -26,7 +26,7 @@ var stringsOperatorScenarios = []expressionScenario{
 		description: "Interpolation - just escape",
 		expression:  `"\\"`,
 		expected: []string{
-			"D0, P[], (!!str)::\\\\\n",
+			"D0, P[], (!!str)::\\\n",
 		},
 	},
 	{
@@ -47,6 +47,15 @@ var stringsOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!str)::Hi (.value)\n",
 		},
 	},
+	{
+		skipDoc:     true,
+		description: "Interpolation - don't!",
+		document:    `value: things`,
+		expression:  `"Hi \\(.value)"`,
+		expected: []string{
+			"D0, P[], (!!str)::Hi \\(.value)\n",
+		},
+	},
 	{
 		skipDoc:     true,
 		description: "Interpolation - random close bracket",
@@ -63,6 +72,13 @@ var stringsOperatorScenarios = []expressionScenario{
 		expression:    `"Hi \("`,
 		expectedError: "unclosed interpolation string \\(",
 	},
+	{
+		skipDoc:       true,
+		description:   "Interpolation - unclosed interpolation string due to escape",
+		document:      `value: things`,
+		expression:    `"Hi \(\)"`,
+		expectedError: "unclosed interpolation string \\(",
+	},
 	{
 		description:    "To up (upper) case",
 		subdescription: "Works with unicode characters",