Reapply monkeypatch to inspect.findsource()

IPython/core/tests/test_ultratb.py

@@ -0,0 +1,51 @@
+"""Tests for IPython.core.ultratb
+"""
+
+import os.path
+import unittest
+
+from IPython.testing import tools as tt
+from IPython.utils.syspathcontext import prepended_to_syspath
+from IPython.utils.tempdir import TemporaryDirectory
+
+ip = get_ipython()
+
+file_1 = """1
+2
+3
+def f():
+  1/0
+"""
+
+file_2 = """def f():
+  1/0
+"""
+
+class ChangedPyFileTest(unittest.TestCase):
+    def test_changing_py_file(self):
+        """Traceback produced if the line where the error occurred is missing?
+
+        https://github.com/ipython/ipython/issues/1456
+        """
+        with TemporaryDirectory() as td:
+            fname = os.path.join(td, "foo.py")
+            with open(fname, "w") as f:
+                f.write(file_1)
+
+            with prepended_to_syspath(td):
+                ip.run_cell("import foo")
+
+            with tt.AssertPrints("ZeroDivisionError"):
+                ip.run_cell("foo.f()")
+
+            # Make the file shorter, so the line of the error is missing.
+            with open(fname, "w") as f:
+                f.write(file_2)
+
+            # For some reason, this was failing on the *second* call after
+            # changing the file, so we call f() twice.
+            with tt.AssertNotPrints("Internal Python error", channel='stderr'):
+                with tt.AssertPrints("ZeroDivisionError"):
+                    ip.run_cell("foo.f()")
+                with tt.AssertPrints("ZeroDivisionError"):
+                    ip.run_cell("foo.f()")

IPython/core/ultratb.py

@@ -126,15 +126,10 @@ def inspect_error():
     error('Internal Python error in the inspect module.\n'
           'Below is the traceback from this internal error.\n')
 
-
-# N.B. This function is a monkeypatch we are currently not applying.
-# It was written some time ago, to fix an apparent Python bug with
-# codeobj.co_firstlineno . Unfortunately, we don't know under what conditions
-# the bug occurred, so we can't tell if it has been fixed. If it reappears, we
-# will apply the monkeypatch again. Also, note that findsource() is not called
-# by our code at this time - we don't know if it was when the monkeypatch was
-# written, or if the monkeypatch is needed for some other code (like a debugger).
-# For the discussion about not applying it, see gh-1229. TK, Jan 2011.
+# This function is a monkeypatch we apply to the Python inspect module. We have
+# now found when it's needed (see discussion on issue gh-1456), and we have a
+# test case (IPython.core.tests.test_ultratb.ChangedPyFileTest) that fails if
+# the monkeypatch is not applied. TK, Aug 2012.
 def findsource(object):
     """Return the entire source file and starting line number for an object.
 
@@ -210,10 +205,8 @@ def findsource(object):
         return lines, lnum
     raise IOError('could not find code object')
 
-# Not applying the monkeypatch - see above the function for details. TK, Jan 2012
-# Monkeypatch inspect to apply our bugfix.  This code only works with py25
-#if sys.version_info[:2] >= (2,5):
-#    inspect.findsource = findsource
+# Monkeypatch inspect to apply our bugfix.  This code only works with Python >= 2.5
+inspect.findsource = findsource
 
 def fix_frame_records_filenames(records):
     """Try to fix the filenames in each record from inspect.getinnerframes().

IPython/testing/tools.py

@@ -306,7 +306,10 @@ def write(self, s):
             super(MyStringIO, self).write(s)
 
 notprinted_msg = """Did not find {0!r} in printed output (on {1}):
-{2!r}"""
+-------
+{2!s}
+-------
+"""
 
 class AssertPrints(object):
     """Context manager for testing that code prints certain text.
@@ -337,7 +340,13 @@ def __exit__(self, etype, value, traceback):
         printed = self.buffer.getvalue()
         assert self.s in printed, notprinted_msg.format(self.s, self.channel, printed)
         return False
-
+
+printed_msg = """Found {0!r} in printed output (on {1}):
+-------
+{2!s}
+-------
+"""
+
 class AssertNotPrints(AssertPrints):
     """Context manager for checking that certain output *isn't* produced.
 
@@ -346,7 +355,7 @@ def __exit__(self, etype, value, traceback):
         self.tee.flush()
         setattr(sys, self.channel, self.orig_stream)
         printed = self.buffer.getvalue()
-        assert self.s not in printed, notprinted_msg.format(self.s, self.channel, printed)
+        assert self.s not in printed, printed_msg.format(self.s, self.channel, printed)
         return False
 
 @contextmanager