python · aldwinaldwin · Aug 13, 2019 · Aug 13, 2019 · Aug 14, 2019 · Aug 14, 2019
diff --git a/Lib/lib2to3/refactor.py b/Lib/lib2to3/refactor.py
@@ -592,12 +592,21 @@ def refactor_doctest(self, block, lineno, indent, filename):
             return block
         if self.refactor_tree(tree, filename):
             new = str(tree).splitlines(keepends=True)
+            # Adjust lineno for lines inserted before
+            jmp = 0
+            for n in new:
+                if n == '\n': break
+                jmp += 1
+            pre = new[:jmp]
             # Undo the adjustment of the line numbers in wrap_toks() below.
-            clipped, new = new[:lineno-1], new[lineno-1:]
+            clipped, new = new[jmp:lineno-1+jmp], new[lineno-1+jmp:]
             assert clipped == ["\n"] * (lineno-1), clipped
             if not new[-1].endswith("\n"):
                 new[-1] += "\n"
-            block = [indent + self.PS1 + new.pop(0)]
+            block = []
+            if pre:
+                block += [indent + self.PS1 + line for line in pre]
+            block += [indent + self.PS1 + new.pop(0)]
             if new:
                 block += [indent + self.PS2 + line for line in new]
         return block

diff --git a/Lib/lib2to3/tests/test_fixers.py b/Lib/lib2to3/tests/test_fixers.py
@@ -428,6 +428,30 @@ def test_unchanged(self):
         s = "reduce()"
         self.unchanged(s)
 
+class Test_doctests(FixerTestCase):
+    fixer = "reduce"
+
+    def check(self, before, after, ignore_warnings=False):
+        before = support.reformat(before)
+        after = support.reformat(after)
+        output = self.refactor.refactor_docstring(before, self.filename)
+        self.assertEqual(after, output)
+
+    def test_reduce(self):
+        # See issue 12611
+        b = """\
+        '''
+        >>> reduce(lambda x, y: x + y, seq)
+        '''
+        """
+        a = """\
+        '''
+        >>> from functools import reduce
+        >>> reduce(lambda x, y: x + y, seq)
+        '''
+        """
+        self.check(b, a)
+
 class Test_print(FixerTestCase):
     fixer = "print"
 

diff --git a/Misc/NEWS.d/next/Library/2019-08-13-09-27-23.bpo-12611.e06VtJ.rst b/Misc/NEWS.d/next/Library/2019-08-13-09-27-23.bpo-12611.e06VtJ.rst
@@ -0,0 +1 @@
+2to3 converting doctest using reduce(). Patch by Aldwin Pollefeyt.
-2to3 converting doctest using reduce(). Patch by Aldwin Pollefeyt.
+Fix 2to3 crashing when run on a doctest that uses reduce(). Patch by Aldwin Pollefeyt.
-2to3 converting doctest using reduce(). Patch by Aldwin Pollefeyt.
+Fix 2to3 crashing when run on a doctest that uses reduce(). Patch by Aldwin Pollefeyt.