prompt: You will be provided with a partial code base and an issue statement explaining a problem to resolve.
  <issue>
  cmd && othercmd throws an exception
  ```
  ➤ ls &&Exception in thread Thread-35:
  Traceback (most recent call last):
    File "/usr/lib/python3.6/threading.py", line 916, in _bootstrap_inner
      self.run()
    File "/usr/lib/python3.6/threading.py", line 864, in run
      self._target(*self._args, **self._kwargs)
    File "/usr/lib/python3.6/site-packages/prompt_toolkit/interface.py", line 860, in run
      completions = list(buffer.completer.get_completions(document, complete_event))
    File "/usr/lib/python3.6/site-packages/xonsh/ptk/completer.py", line 49, in get_completions
      self.ctx)
    File "/usr/lib/python3.6/site-packages/xonsh/__amalgam__.py", line 124, in complete
      out = func(prefix, line, begidx, endidx, ctx)
    File "/usr/lib/python3.6/site-packages/xonsh/completers/__amalgam__.py", line 831, in complete_skipper
      ctx)
    File "/usr/lib/python3.6/site-packages/xonsh/__amalgam__.py", line 124, in complete
      out = func(prefix, line, begidx, endidx, ctx)
    File "/usr/lib/python3.6/site-packages/xonsh/completers/__amalgam__.py", line 1427, in complete_base
      complete_command(prefix, line, start, end, ctx))
  TypeError: unsupported operand type(s) for |: 'tuple' and 'set'
  ```
  
  ```
  ➤ y -Q | egrep 'toolkit|xon'
  community/python-prompt_toolkit 1.0.14-1
  local/xonsh 0.5.9-1
  ```
  
  Let me know if you need anything else.
  
  </issue>
  <code>
  [start of xonsh/completers/base.py]
  1 """Base completer for xonsh."""
  2 import collections.abc as cabc
  3 
  4 from xonsh.completers.path import complete_path
  5 from xonsh.completers.python import complete_python
  6 from xonsh.completers.commands import complete_command
  7 
  8 
  9 def complete_base(prefix, line, start, end, ctx):
  10     """If the line is empty, complete based on valid commands, python names,
  11     and paths.  If we are completing the first argument, complete based on
  12     valid commands and python names.
  13     """
  14     if line.strip() == "":
  15         out = complete_python(prefix, line, start, end, ctx) | complete_command(
  16             prefix, line, start, end, ctx
  17         )
  18         paths = complete_path(prefix, line, start, end, ctx, False)
  19         return (out | paths[0]), paths[1]
  20     elif prefix == line:
  21         python_comps = complete_python(prefix, line, start, end, ctx)
  22         if isinstance(python_comps, cabc.Sequence):
  23             return (
  24                 python_comps[0] | complete_command(prefix, line, start, end, ctx),
  25                 python_comps[1],
  26             )
  27         else:
  28             return python_comps | complete_command(prefix, line, start, end, ctx)
  29     return set()
  30
  [end of xonsh/completers/base.py]
  </code>
  
  I need you to solve this issue by generating a single patch file that I can apply directly to this repository using git apply. Please respond with a single patch file in the following format.
  <patch>
  diff --git a/file.py b/file.py
  --- a/file.py
  +++ b/file.py
  @@ -1,27 +1,35 @@
   def euclidean(a, b):
  -    while b:
  -        a, b = b, a % b
  -    return a
  +    if b == 0:
  +        return a
  +    return euclidean(b, a % b)
   
   
   def bresenham(x0, y0, x1, y1):
       points = []
       dx = abs(x1 - x0)
       dy = abs(y1 - y0)
  -    sx = 1 if x0 < x1 else -1
  -    sy = 1 if y0 < y1 else -1
  -    err = dx - dy
  +    x, y = x0, y0
  +    sx = -1 if x0 > x1 else 1
  +    sy = -1 if y0 > y1 else 1
   
  -    while True:
  -        points.append((x0, y0))
  -        if x0 == x1 and y0 == y1:
  -            break
  -        e2 = 2 * err
  -        if e2 > -dy:
  -            err -= dy
  -            x0 += sx
  -        if e2 < dx:
  -            err += dx
  -            y0 += sy
  +    if dx > dy:
  +        err = dx / 2.0
  +        while x != x1:
  +            points.append((x, y))
  +            err -= dy
  +            if err < 0:
  +                y += sy
  +                err += dx
  +            x += sx
  +    else:
  +        err = dy / 2.0
  +        while y != y1:
  +            points.append((x, y))
  +            err -= dx
  +            if err < 0:
  +                x += sx
  +                err += dy
  +            y += sy
  +
  +    points.append((x, y))
       return points
  
  </patch>
golden_diff: diff --git a/xonsh/completers/base.py b/xonsh/completers/base.py
  --- a/xonsh/completers/base.py
  +++ b/xonsh/completers/base.py
  @@ -11,19 +11,21 @@
       and paths.  If we are completing the first argument, complete based on
       valid commands and python names.
       """
  +    # get and unpack python completions
  +    python_comps = complete_python(prefix, line, start, end, ctx)
  +    if isinstance(python_comps, cabc.Sequence):
  +        python_comps, python_comps_len = python_comps
  +    else:
  +        python_comps_len = None
  +    # add command completions
  +    out = python_comps | complete_command(prefix, line, start, end, ctx)
  +    # add paths, if needed
       if line.strip() == "":
  -        out = complete_python(prefix, line, start, end, ctx) | complete_command(
  -            prefix, line, start, end, ctx
  -        )
           paths = complete_path(prefix, line, start, end, ctx, False)
           return (out | paths[0]), paths[1]
       elif prefix == line:
  -        python_comps = complete_python(prefix, line, start, end, ctx)
  -        if isinstance(python_comps, cabc.Sequence):
  -            return (
  -                python_comps[0] | complete_command(prefix, line, start, end, ctx),
  -                python_comps[1],
  -            )
  +        if python_comps_len is None:
  +            return out
           else:
  -            return python_comps | complete_command(prefix, line, start, end, ctx)
  +            return out, python_comps_len
       return set()
  
verification_info: {"golden_diff": "diff --git a/xonsh/completers/base.py b/xonsh/completers/base.py\n--- a/xonsh/completers/base.py\n+++ b/xonsh/completers/base.py\n@@ -11,19 +11,21 @@\n     and paths.  If we are completing the first argument, complete based on\n     valid commands and python names.\n     \"\"\"\n+    # get and unpack python completions\n+    python_comps = complete_python(prefix, line, start, end, ctx)\n+    if isinstance(python_comps, cabc.Sequence):\n+        python_comps, python_comps_len = python_comps\n+    else:\n+        python_comps_len = None\n+    # add command completions\n+    out = python_comps | complete_command(prefix, line, start, end, ctx)\n+    # add paths, if needed\n     if line.strip() == \"\":\n-        out = complete_python(prefix, line, start, end, ctx) | complete_command(\n-            prefix, line, start, end, ctx\n-        )\n         paths = complete_path(prefix, line, start, end, ctx, False)\n         return (out | paths[0]), paths[1]\n     elif prefix == line:\n-        python_comps = complete_python(prefix, line, start, end, ctx)\n-        if isinstance(python_comps, cabc.Sequence):\n-            return (\n-                python_comps[0] | complete_command(prefix, line, start, end, ctx),\n-                python_comps[1],\n-            )\n+        if python_comps_len is None:\n+            return out\n         else:\n-            return python_comps | complete_command(prefix, line, start, end, ctx)\n+            return out, python_comps_len\n     return set()\n", "issue": "cmd && othercmd throws an exception\n```\r\n\u27a4 ls &&Exception in thread Thread-35:\r\nTraceback (most recent call last):\r\n  File \"/usr/lib/python3.6/threading.py\", line 916, in _bootstrap_inner\r\n    self.run()\r\n  File \"/usr/lib/python3.6/threading.py\", line 864, in run\r\n    self._target(*self._args, **self._kwargs)\r\n  File \"/usr/lib/python3.6/site-packages/prompt_toolkit/interface.py\", line 860, in run\r\n    completions = list(buffer.completer.get_completions(document, complete_event))\r\n  File \"/usr/lib/python3.6/site-packages/xonsh/ptk/completer.py\", line 49, in get_completions\r\n    self.ctx)\r\n  File \"/usr/lib/python3.6/site-packages/xonsh/__amalgam__.py\", line 124, in complete\r\n    out = func(prefix, line, begidx, endidx, ctx)\r\n  File \"/usr/lib/python3.6/site-packages/xonsh/completers/__amalgam__.py\", line 831, in complete_skipper\r\n    ctx)\r\n  File \"/usr/lib/python3.6/site-packages/xonsh/__amalgam__.py\", line 124, in complete\r\n    out = func(prefix, line, begidx, endidx, ctx)\r\n  File \"/usr/lib/python3.6/site-packages/xonsh/completers/__amalgam__.py\", line 1427, in complete_base\r\n    complete_command(prefix, line, start, end, ctx))\r\nTypeError: unsupported operand type(s) for |: 'tuple' and 'set'\r\n```\r\n\r\n```\r\n\u27a4 y -Q | egrep 'toolkit|xon'\r\ncommunity/python-prompt_toolkit 1.0.14-1\r\nlocal/xonsh 0.5.9-1\r\n```\r\n\r\nLet me know if you need anything else.\n", "before_files": [{"content": "\"\"\"Base completer for xonsh.\"\"\"\nimport collections.abc as cabc\n\nfrom xonsh.completers.path import complete_path\nfrom xonsh.completers.python import complete_python\nfrom xonsh.completers.commands import complete_command\n\n\ndef complete_base(prefix, line, start, end, ctx):\n    \"\"\"If the line is empty, complete based on valid commands, python names,\n    and paths.  If we are completing the first argument, complete based on\n    valid commands and python names.\n    \"\"\"\n    if line.strip() == \"\":\n        out = complete_python(prefix, line, start, end, ctx) | complete_command(\n            prefix, line, start, end, ctx\n        )\n        paths = complete_path(prefix, line, start, end, ctx, False)\n        return (out | paths[0]), paths[1]\n    elif prefix == line:\n        python_comps = complete_python(prefix, line, start, end, ctx)\n        if isinstance(python_comps, cabc.Sequence):\n            return (\n                python_comps[0] | complete_command(prefix, line, start, end, ctx),\n                python_comps[1],\n            )\n        else:\n            return python_comps | complete_command(prefix, line, start, end, ctx)\n    return set()\n", "path": "xonsh/completers/base.py"}]}