PY-15564 Remove text after the first backslash inside whitespace during line joining

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

@@ -119,6 +119,12 @@ public class PyJoinLinesHandler implements JoinRawLinesHandlerDelegate {
         }
       }
     }
+    final String sequence = text.subSequence(i + 1, end).toString();
+    final int index = sequence.indexOf('\\');
+    if (index >= 0) {
+      document.replaceString(i + 1, end, sequence.substring(0, index));
+      return i + 1 + index;
+    }
     return CANNOT_JOIN;
   }
 

python/testData/joinLines/BackslashBetweenTargetsInFromImport-after.py

@@ -0,0 +1 @@
+from foo import bar, baz

python/testData/joinLines/BackslashBetweenTargetsInFromImport.py

@@ -0,0 +1,2 @@
+from foo import bar, \
+    baz

python/testData/joinLines/BackslashBetweenTargetsInImport-after.py

@@ -0,0 +1 @@
+import foo, bar

python/testData/joinLines/BackslashBetweenTargetsInImport.py

@@ -0,0 +1,2 @@
+import foo, \
+    bar

python/testSrc/com/jetbrains/python/PyJoinLinesTest.java

@@ -138,4 +138,14 @@ public class PyJoinLinesTest extends PyTestCase {
   public void testListComprehension() {
     doTest();
   }
+
+  // PY-15564
+  public void testBackslashBetweenTargetsInImport() {
+    doTest();
+  }
+
+  // PY-15564
+  public void testBackslashBetweenTargetsInFromImport() {
+    doTest();
+  }
 }