PY-11481 Correctly detect escaped quotes at the end of string literals

python/src/com/jetbrains/python/validation/StringLiteralQuotesAnnotator.java

@@ -58,9 +58,17 @@ public class StringLiteralQuotesAnnotator extends PyAnnotator {
 
   private boolean checkQuotedString(@NotNull ASTNode stringNode, @NotNull String nodeText) {
     final char firstQuote = nodeText.charAt(0);
-    final int lastChar = nodeText.length() - 1;
-    if (lastChar == 0 || nodeText.charAt(lastChar) != firstQuote ||
-        (nodeText.charAt(lastChar - 1) == '\\' && (lastChar == 1 || nodeText.charAt(lastChar - 2) != '\\'))) {
+    final char lastChar = nodeText.charAt(nodeText.length() - 1);
+    int precedingBackslashCount = 0;
+    for (int i = nodeText.length() - 2; i >= 0; i--) {
+      if (nodeText.charAt(i) == '\\') {
+        precedingBackslashCount++;
+      }
+      else {
+        break;
+      }
+    }
+    if (nodeText.length() == 1 || lastChar != firstQuote || precedingBackslashCount % 2 != 0) {
       getHolder().createErrorAnnotation(stringNode, PyBundle.message("ANN.missing.closing.quote", firstQuote));
       return true;
     }

python/testData/highlighting/multipleEscapedBackslashes.py

@@ -0,0 +1,2 @@
+S1 = 'This literal contains even number of backslashes\\\\\\'
+S2 = <error descr="Missing closing quote [']">'This literal contains odd number of backslashes\\\\\\\'</error>

python/testSrc/com/jetbrains/python/PythonHighlightingTest.java

@@ -174,6 +174,10 @@ public class PythonHighlightingTest extends PyTestCase {
     doTest(true, false);
   }
 
+  public void testMultipleEscapedBackslashes() {
+    doTest(true, false);
+  }
+
   public void testUnsupportedFeaturesInPython3() {
     doTest(LanguageLevel.PYTHON30, true, false);
   }