PY-18972 Automatically close quotes for f-string literals

python/src/com/jetbrains/python/editor/BaseQuoteHandler.java

@@ -88,15 +88,11 @@ public class BaseQuoteHandler extends SimpleTokenSetQuoteHandler implements Mult
   }
 
   private static int getLiteralStartOffset(CharSequence text, int start) {
-    char c = Character.toUpperCase(text.charAt(start));
-    if (c == 'U' || c == 'B') {
-      start++;
-      c = Character.toUpperCase(text.charAt(start));
+    int index = start;
+    while (index < start + 2 && "URBF".indexOf(Character.toUpperCase(text.charAt(index))) >= 0) {
+      index++;
     }
-    if (c == 'R') {
-      start++;
-    }
-    return start;
+    return index;
   }
 
   @Override

python/testSrc/com/jetbrains/python/PyEditingTest.java

@@ -87,6 +87,14 @@ public class PyEditingTest extends PyTestCase {
     assertEquals("'''docstring'''", doTestTyping("'''docstring''", 14,  '\''));
   }
 
+  // PY-18972
+  public void testFString() throws Exception {
+    assertEquals("f''", doTestTyping("f", 1, '\''));
+    assertEquals("rf''", doTestTyping("rf", 2, '\''));
+    assertEquals("fr''", doTestTyping("fr", 2, '\''));
+    assertEquals("fr''''''", doTestTyping("fr''", 4, '\''));
+  }
+
   public void testOvertypeFromInside() {
     assertEquals("''", doTestTyping("''", 1, '\''));
   }