Fixed code and tests for bad utf-8.

Author: jba

diffmatchpatch/dmp.go

@@ -1434,7 +1434,13 @@ func (dmp *DiffMatchPatch) DiffFromDelta(text1, delta string) (diffs []Diff, err
 		case '+':
 			// decode would Diff all "+" to " "
 			param = strings.Replace(param, "+", "%2b", -1)
-			param, _ = url.QueryUnescape(param)
+			param, err = url.QueryUnescape(param)
+			if err != nil {
+				return nil, err
+			}
+			if !utf8.ValidString(param) {
+				return nil, fmt.Errorf("invalid UTF-8 token: %q", param)
+			}
 			diffs = append(diffs, Diff{DiffInsert, param})
 		case '=', '-':
 			n, err := strconv.ParseInt(param, 10, 0)

diffmatchpatch/dmp_test.go

@@ -732,13 +732,17 @@ func Test_diffDelta(t *testing.T) {
 		t.Fatal("diff_fromDelta: Too short.")
 	}
 
-	// Generates error (%c3%xy invalid Unicode).
-	/*
-		seq, err := dmp.DiffFromDelta("", "+%c3%xy")
-		if err == nil {
-			panic(1) //assert.Fail("diff_fromDelta: Invalid character.");
-		}
-	*/
+	// Generates error (%xy invalid URL escape).
+	_, err = dmp.DiffFromDelta("", "+%c3%xy")
+	if err == nil {
+		assert.Fail(t, "diff_fromDelta: expected Invalid URL escape.");
+	}
+
+	// Generates error (invalid utf8).
+	_, err = dmp.DiffFromDelta("", "+%c3xy")
+	if err == nil {
+		assert.Fail(t, "diff_fromDelta: expected Invalid utf8.");
+	}
 
 	// Test deltas with special characters.
 	diffs = []Diff{