Merge pull request #6065 from atteroTheGreatest/i1673

#1673 Display of chained exception

IPython/core/interactiveshell.py

@@ -2918,7 +2918,6 b' class InteractiveShell(SingletonConfigurable):'
         False : successful execution.
         True : an error occurred.
         """
-
         # Set our own excepthook in case the user code tries to call it
         # directly, so that the IPython crash handler doesn't get triggered
         old_excepthook,sys.excepthook = sys.excepthook, self.excepthook

IPython/core/tests/test_ultratb.py

@@ -9,6 +9,7 b' from IPython.testing import tools as tt'
 from IPython.testing.decorators import onlyif_unicode_paths
 from IPython.utils.syspathcontext import prepended_to_syspath
 from IPython.utils.tempdir import TemporaryDirectory
+from IPython.utils.py3compat import PY3
 
 ip = get_ipython()
 
@@ -147,3 +148,37 b' class SyntaxErrorTest(unittest.TestCase):'
         except ValueError:
             with tt.AssertPrints('QWERTY'):
                 ip.showsyntaxerror()
+
+
+class Python3ChainedExceptionsTest(unittest.TestCase):
+    DIRECT_CAUSE_ERROR_CODE = """
+try:
+    x = 1 + 2
+    print(not_defined_here)
+except Exception as e:
+    x += 55
+    x - 1
+    y = {}
+    raise KeyError('uh') from e
+    """
+
+    EXCEPTION_DURING_HANDLING_CODE = """
+try:
+    x = 1 + 2
+    print(not_defined_here)
+except Exception as e:
+    x += 55
+    x - 1
+    y = {}
+    raise KeyError('uh')
+    """
+
+    def test_direct_cause_error(self):
+        if PY3:
+            with tt.AssertPrints(["KeyError", "NameError", "direct cause"]):
+                ip.run_cell(self.DIRECT_CAUSE_ERROR_CODE)
+
+    def test_exception_during_handling_error(self):
+        if PY3:
+            with tt.AssertPrints(["KeyError", "NameError", "During handling"]):
+                ip.run_cell(self.EXCEPTION_DURING_HANDLING_CODE)

IPython/core/ultratb.py

@@ -39,7 +39,7 b" Give it a shot--you'll love it or you'll hate it."
   Verbose).
 
 
-Installation instructions for ColorTB::
+Installation instructions for VerboseTB::
 
     import sys,ultratb
     sys.excepthook = ultratb.VerboseTB()
@@ -141,6 +141,7 b' def inspect_error():'
     error('Internal Python error in the inspect module.\n'
           'Below is the traceback from this internal error.\n')
 
+
 # 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
@@ -220,9 +221,11 b' def findsource(object):'
         return lines, lnum
     raise IOError('could not find code object')
 
+
 # Monkeypatch inspect to apply our bugfix.
 def with_patch_inspect(f):
     """decorator for monkeypatching inspect.findsource"""
+
     def wrapped(*args, **kwargs):
         save_findsource = inspect.findsource
         inspect.findsource = findsource
@@ -230,8 +233,10 b' def with_patch_inspect(f):'
             return f(*args, **kwargs)
         finally:
             inspect.findsource = save_findsource
+
     return wrapped
 
+
 def fix_frame_records_filenames(records):
     """Try to fix the filenames in each record from inspect.getinnerframes().
 
@@ -257,7 +262,6 b' def _fixed_getinnerframes(etb, context=1,tb_offset=0):'
     LNUM_POS, LINES_POS, INDEX_POS =  2, 4, 5
 
     records  = fix_frame_records_filenames(inspect.getinnerframes(etb, context))
-
     # If the error is at the console, don't build any context, since it would
     # otherwise produce 5 blank lines printed out (there is no file at the
     # console)
@@ -290,6 +294,7 b' def _fixed_getinnerframes(etb, context=1,tb_offset=0):'
 
 _parser = PyColorize.Parser()
 
+
 def _format_traceback_lines(lnum, index, lines, Colors, lvals=None,scheme=None):
     numbers_width = INDENT_SIZE - 1
     res = []
@@ -510,7 +515,7 b' class ListTB(TBTools):'
         ## out_list.append(lines[-1])
 
         # This means it was indenting everything but the last line by a little
-        # bit.  I've disabled this for now, but if we see ugliness somewhre we
+        # bit.  I've disabled this for now, but if we see ugliness somewhere we
         # can restore it.
 
         return out_list
@@ -550,7 +555,6 b' class ListTB(TBTools):'
             item += '%s    %s%s\n' % (Colors.line, line.strip(),
                                             Colors.Normal)
         list.append(item)
-        #from pprint import pformat; print 'LISTTB', pformat(list) # dbg
         return list
 
     def _format_exception_only(self, etype, value):
@@ -576,7 +580,6 b' class ListTB(TBTools):'
         else:
             if issubclass(etype, SyntaxError):
                 have_filedata = True
-                #print 'filename is',filename  # dbg
                 if not value.filename: value.filename = "<string>"
                 if value.lineno:
                     lineno = value.lineno
@@ -636,7 +639,6 b' class ListTB(TBTools):'
         """
         return ListTB.structured_traceback(self, etype, value, [])
 
-
     def show_exception_only(self, etype, evalue):
         """Only print the exception type and message, without a traceback.
 
@@ -659,6 +661,7 b' class ListTB(TBTools):'
         except:
             return '<unprintable %s object>' % type(value).__name__
 
+
 #----------------------------------------------------------------------------
 class VerboseTB(TBTools):
     """A port of Ka-Ping Yee's cgitb.py module that outputs color text instead
@@ -691,103 +694,14 b' class VerboseTB(TBTools):'
             check_cache = linecache.checkcache
         self.check_cache = check_cache
 
-    def structured_traceback(self, etype, evalue, etb, tb_offset=None,
-                             context=5):
-        """Return a nice text document describing the traceback."""
-
-        tb_offset = self.tb_offset if tb_offset is None else tb_offset
-
-        # some locals
-        try:
-            etype = etype.__name__
-        except AttributeError:
-            pass
+    def format_records(self, records):
         Colors        = self.Colors   # just a shorthand + quicker name lookup
         ColorsNormal  = Colors.Normal  # used a lot
         col_scheme    = self.color_scheme_table.active_scheme_name
         indent        = ' '*INDENT_SIZE
         em_normal     = '%s\n%s%s' % (Colors.valEm, indent,ColorsNormal)
         undefined     = '%sundefined%s' % (Colors.em, ColorsNormal)
-        exc = '%s%s%s' % (Colors.excName,etype,ColorsNormal)
-
-        # some internal-use functions
-        def text_repr(value):
-            """Hopefully pretty robust repr equivalent."""
-            # this is pretty horrible but should always return *something*
-            try:
-                return pydoc.text.repr(value)
-            except KeyboardInterrupt:
-                raise
-            except:
-                try:
-                    return repr(value)
-                except KeyboardInterrupt:
-                    raise
-                except:
-                    try:
-                        # all still in an except block so we catch
-                        # getattr raising
-                        name = getattr(value, '__name__', None)
-                        if name:
-                            # ick, recursion
-                            return text_repr(name)
-                        klass = getattr(value, '__class__', None)
-                        if klass:
-                            return '%s instance' % text_repr(klass)
-                    except KeyboardInterrupt:
-                        raise
-                    except:
-                        return 'UNRECOVERABLE REPR FAILURE'
-        def eqrepr(value, repr=text_repr): return '=%s' % repr(value)
-        def nullrepr(value, repr=text_repr): return ''
-
-        # meat of the code begins
-        try:
-            etype = etype.__name__
-        except AttributeError:
-            pass
-
-        if self.long_header:
-            # Header with the exception type, python version, and date
-            pyver = 'Python ' + sys.version.split()[0] + ': ' + sys.executable
-            date = time.ctime(time.time())
-
-            head = '%s%s%s\n%s%s%s\n%s' % (Colors.topline, '-'*75, ColorsNormal,
-                                           exc, ' '*(75-len(str(etype))-len(pyver)),
-                                           pyver, date.rjust(75) )
-            head += "\nA problem occured executing Python code.  Here is the sequence of function"\
-                    "\ncalls leading up to the error, with the most recent (innermost) call last."
-        else:
-            # Simplified header
-            head = '%s%s%s\n%s%s' % (Colors.topline, '-'*75, ColorsNormal,exc,
-                                     'Traceback (most recent call last)'.\
-                                                  rjust(75 - len(str(etype)) ) )
         frames = []
-        # Flush cache before calling inspect.  This helps alleviate some of the
-        # problems with python 2.3's inspect.py.
-        ##self.check_cache()
-        # Drop topmost frames if requested
-        try:
-            # Try the default getinnerframes and Alex's: Alex's fixes some
-            # problems, but it generates empty tracebacks for console errors
-            # (5 blanks lines) where none should be returned.
-            #records = inspect.getinnerframes(etb, context)[tb_offset:]
-            #print 'python records:', records # dbg
-            records = _fixed_getinnerframes(etb, context, tb_offset)
-            #print 'alex   records:', records # dbg
-        except:
-
-            # FIXME: I've been getting many crash reports from python 2.3
-            # users, traceable to inspect.py.  If I can find a small test-case
-            # to reproduce this, I should either write a better workaround or
-            # file a bug report against inspect (if that's the real problem).
-            # So far, I haven't been able to find an isolated example to
-            # reproduce the problem.
-            inspect_error()
-            traceback.print_exc(file=self.ostream)
-            info('\nUnfortunately, your original traceback can not be constructed.\n')
-            return ''
-
         # build some color string templates outside these nested loops
         tpl_link       = '%s%%s%s' % (Colors.filenameEm,ColorsNormal)
         tpl_call       = 'in %s%%s%s%%s%s' % (Colors.vName, Colors.valEm,
@@ -798,11 +712,11 b' class VerboseTB(TBTools):'
         tpl_global_var = '%sglobal%s %s%%s%s' % (Colors.em, ColorsNormal,
                                                  Colors.vName, ColorsNormal)
         tpl_name_val   = '%%s %s= %%s%s' % (Colors.valEm, ColorsNormal)
+
         tpl_line       = '%s%%s%s %%s' % (Colors.lineno, ColorsNormal)
         tpl_line_em    = '%s%%s%s %%s%s' % (Colors.linenoEm,Colors.line,
                                             ColorsNormal)
 
-        # now, loop over all records printing context and info
         abspath = os.path.abspath
         for frame, file, lnum, func, lines, index in records:
             #print '*** record:',file,lnum,func,lines,index  # dbg
@@ -943,6 +857,43 b' class VerboseTB(TBTools):'
                     _format_traceback_lines(lnum,index,lines,Colors,lvals,
                                             col_scheme))))
 
+        return frames
+
+    def prepare_chained_exception_message(self, cause):
+        direct_cause = "\nThe above exception was the direct cause of the following exception:\n"
+        exception_during_handling = "\nDuring handling of the above exception, another exception occurred:\n"
+
+        if cause:
+            message = [[direct_cause]]
+        else:
+            message = [[exception_during_handling]]
+        return message
+
+    def prepare_header(self, etype, long_version=False):
+        colors = self.Colors  # just a shorthand + quicker name lookup
+        colorsnormal = colors.Normal  # used a lot
+        exc = '%s%s%s' % (colors.excName, etype, colorsnormal)
+        if long_version:
+            # Header with the exception type, python version, and date
+            pyver = 'Python ' + sys.version.split()[0] + ': ' + sys.executable
+            date = time.ctime(time.time())
+
+            head = '%s%s%s\n%s%s%s\n%s' % (colors.topline, '-' * 75, colorsnormal,
+                                           exc, ' ' * (75 - len(str(etype)) - len(pyver)),
+                                           pyver, date.rjust(75) )
+            head += "\nA problem occurred executing Python code.  Here is the sequence of function" \
+                    "\ncalls leading up to the error, with the most recent (innermost) call last."
+        else:
+            # Simplified header
+            head = '%s%s' % (exc, 'Traceback (most recent call last)'. \
+                             rjust(75 - len(str(etype))) )
+
+        return head
+
+    def format_exception(self, etype, evalue):
+        colors = self.Colors  # just a shorthand + quicker name lookup
+        colorsnormal = colors.Normal  # used a lot
+        indent = ' ' * INDENT_SIZE
         # Get (safely) a string form of the exception info
         try:
             etype_str,evalue_str = map(str,(etype,evalue))
@@ -951,38 +902,123 b' class VerboseTB(TBTools):'
             etype,evalue = str,sys.exc_info()[:2]
             etype_str,evalue_str = map(str,(etype,evalue))
         # ... and format it
-        exception = ['%s%s%s: %s' % (Colors.excName, etype_str,
-                                     ColorsNormal, py3compat.cast_unicode(evalue_str))]
+        exception = ['%s%s%s: %s' % (colors.excName, etype_str,
+                                     colorsnormal, py3compat.cast_unicode(evalue_str))]
+
         if (not py3compat.PY3) and type(evalue) is types.InstanceType:
             try:
                 names = [w for w in dir(evalue) if isinstance(w, py3compat.string_types)]
             except:
-                # Every now and then, an object with funny inernals blows up
+                # Every now and then, an object with funny internals blows up
                 # when dir() is called on it.  We do the best we can to report
                 # the problem and continue
                 _m = '%sException reporting error (object with broken dir())%s:'
-                exception.append(_m % (Colors.excName,ColorsNormal))
+                exception.append(_m % (colors.excName, colorsnormal))
                 etype_str,evalue_str = map(str,sys.exc_info()[:2])
-                exception.append('%s%s%s: %s' % (Colors.excName,etype_str,
-                                     ColorsNormal, py3compat.cast_unicode(evalue_str)))
+                exception.append('%s%s%s: %s' % (colors.excName, etype_str,
+                                                 colorsnormal, py3compat.cast_unicode(evalue_str)))
                 names = []
             for name in names:
                 value = text_repr(getattr(evalue, name))
                 exception.append('\n%s%s = %s' % (indent, name, value))
 
-        # vds: >>
+        return exception
+
+    def format_exception_as_a_whole(self, etype, evalue, etb, number_of_lines_of_context, tb_offset):
+        # some locals
+        try:
+            etype = etype.__name__
+        except AttributeError:
+            pass
+
+        tb_offset = self.tb_offset if tb_offset is None else tb_offset
+        head = self.prepare_header(etype, self.long_header)
+        records = self.get_records(etb, number_of_lines_of_context, tb_offset)
+
+        frames = self.format_records(records)
+        if records is None:
+            return ""
+
+        formatted_exception = self.format_exception(etype, evalue)
         if records:
              filepath, lnum = records[-1][1:3]
-             #print "file:", str(file), "linenb", str(lnum) # dbg
              filepath = os.path.abspath(filepath)
              ipinst = get_ipython()
              if ipinst is not None:
                  ipinst.hooks.synchronize_with_editor(filepath, lnum, 0)
-        # vds: <<
 
-        # return all our info assembled as a single string
-        # return '%s\n\n%s\n%s' % (head,'\n'.join(frames),''.join(exception[0]) )
-        return [head] + frames + [''.join(exception[0])]
+        return [[head] + frames + [''.join(formatted_exception[0])]]
+
+    def get_records(self, etb, number_of_lines_of_context, tb_offset):
+        try:
+            # Try the default getinnerframes and Alex's: Alex's fixes some
+            # problems, but it generates empty tracebacks for console errors
+            # (5 blanks lines) where none should be returned.
+            return _fixed_getinnerframes(etb, number_of_lines_of_context, tb_offset)
+        except:
+            # FIXME: I've been getting many crash reports from python 2.3
+            # users, traceable to inspect.py.  If I can find a small test-case
+            # to reproduce this, I should either write a better workaround or
+            # file a bug report against inspect (if that's the real problem).
+            # So far, I haven't been able to find an isolated example to
+            # reproduce the problem.
+            inspect_error()
+            traceback.print_exc(file=self.ostream)
+            info('\nUnfortunately, your original traceback can not be constructed.\n')
+            return None
+
+    def get_parts_of_chained_exception(self, evalue):
+        def get_chained_exception(exception_value):
+            cause = getattr(exception_value, '__cause__', None)
+            if cause:
+                return cause
+            return getattr(exception_value, '__context__', None)
+
+        chained_evalue = get_chained_exception(evalue)
+
+        if chained_evalue:
+            return chained_evalue.__class__, chained_evalue, chained_evalue.__traceback__
+
+    def structured_traceback(self, etype, evalue, etb, tb_offset=None,
+                             number_of_lines_of_context=5):
+        """Return a nice text document describing the traceback."""
+
+        formatted_exception = self.format_exception_as_a_whole(etype, evalue, etb, number_of_lines_of_context,
+                                                               tb_offset)
+
+        colors = self.Colors  # just a shorthand + quicker name lookup
+        colorsnormal = colors.Normal  # used a lot
+        head = '%s%s%s' % (colors.topline, '-' * 75, colorsnormal)
+        structured_traceback_parts = [head]
+        if py3compat.PY3:
+            chained_exceptions_tb_offset = 0
+            lines_of_context = 3
+            formatted_exceptions = formatted_exception
+            exception = self.get_parts_of_chained_exception(evalue)
+            if exception:
+                formatted_exceptions += self.prepare_chained_exception_message(evalue.__cause__)
+                etype, evalue, etb = exception
+            else:
+                evalue = None
+            while evalue:
+                formatted_exceptions += self.format_exception_as_a_whole(etype, evalue, etb, lines_of_context,
+                                                                         chained_exceptions_tb_offset)
+                exception = self.get_parts_of_chained_exception(evalue)
+
+                if exception:
+                    formatted_exceptions += self.prepare_chained_exception_message(evalue.__cause__)
+                    etype, evalue, etb = exception
+                else:
+                    evalue = None
+
+            # we want to see exceptions in a reversed order:
+            # the first exception should be on top
+            for formatted_exception in reversed(formatted_exceptions):
+                structured_traceback_parts += formatted_exception
+        else:
+            structured_traceback_parts += formatted_exception[0]
+
+        return structured_traceback_parts
 
     def debugger(self,force=False):
         """Call up the pdb debugger if desired, always clean up the tb
@@ -1050,6 +1086,7 b' class VerboseTB(TBTools):'
         except KeyboardInterrupt:
             print("\nKeyboardInterrupt")
 
+
 #----------------------------------------------------------------------------
 class FormattedTB(VerboseTB, ListTB):
     """Subclass ListTB but allow calling with a traceback.
@@ -1089,13 +1126,13 b' class FormattedTB(VerboseTB, ListTB):'
         else:
             return None
 
-    def structured_traceback(self, etype, value, tb, tb_offset=None, context=5):
+    def structured_traceback(self, etype, value, tb, tb_offset=None, number_of_lines_of_context=5):
         tb_offset = self.tb_offset if tb_offset is None else tb_offset
         mode = self.mode
         if mode in self.verbose_modes:
             # Verbose modes need a full traceback
             return VerboseTB.structured_traceback(
-                self, etype, value, tb, tb_offset, context
+                self, etype, value, tb, tb_offset, number_of_lines_of_context
             )
         else:
             # We must check the source cache because otherwise we can print
@@ -1104,7 +1141,7 b' class FormattedTB(VerboseTB, ListTB):'
             # Now we can extract and format the exception
             elist = self._extract_tb(tb)
             return ListTB.structured_traceback(
-                self, etype, value, elist, tb_offset, context
+                self, etype, value, elist, tb_offset, number_of_lines_of_context
             )
 
     def stb2text(self, stb):
@@ -1131,7 +1168,7 b' class FormattedTB(VerboseTB, ListTB):'
         # Set the join character for generating text tracebacks
         self.tb_join_char = self._join_chars[self.mode]
 
-    # some convenient shorcuts
+    # some convenient shortcuts
     def plain(self):
         self.set_mode(self.valid_modes[0])
 
@@ -1141,6 +1178,7 b' class FormattedTB(VerboseTB, ListTB):'
     def verbose(self):
         self.set_mode(self.valid_modes[2])
 
+
 #----------------------------------------------------------------------------
 class AutoFormattedTB(FormattedTB):
     """A traceback printer which can be called on the fly.
@@ -1167,7 +1205,6 b' class AutoFormattedTB(FormattedTB):'
           per-call basis (this overrides temporarily the instance's tb_offset
           given at initialization time.  """
 
-
         if out is None:
             out = self.ostream
         out.flush()
@@ -1182,18 +1219,20 b' class AutoFormattedTB(FormattedTB):'
             print("\nKeyboardInterrupt")
 
     def structured_traceback(self, etype=None, value=None, tb=None,
-                             tb_offset=None, context=5):
+                             tb_offset=None, number_of_lines_of_context=5):
         if etype is None:
             etype,value,tb = sys.exc_info()
         self.tb = tb
         return FormattedTB.structured_traceback(
-            self, etype, value, tb, tb_offset, context)
+            self, etype, value, tb, tb_offset, number_of_lines_of_context)
+
 
 #---------------------------------------------------------------------------
 
 # A simple class to preserve Nathan's original functionality.
 class ColorTB(FormattedTB):
     """Shorthand to initialize a FormattedTB in Linux colors mode."""
+
     def __init__(self,color_scheme='Linux',call_pdb=0):
         FormattedTB.__init__(self,color_scheme=color_scheme,
                              call_pdb=call_pdb)
@@ -1208,6 +1247,7 b' class SyntaxTB(ListTB):'
 
     def __call__(self, etype, value, elist):
         self.last_syntax_error = value
+
         ListTB.__call__(self,etype,value,elist)
 
     def structured_traceback(self, etype, value, elist, tb_offset=None,
@@ -1236,7 +1276,46 b' class SyntaxTB(ListTB):'
         return ''.join(stb)
 
 
+# some internal-use functions
+def text_repr(value):
+    """Hopefully pretty robust repr equivalent."""
+    # this is pretty horrible but should always return *something*
+    try:
+        return pydoc.text.repr(value)
+    except KeyboardInterrupt:
+        raise
+    except:
+        try:
+            return repr(value)
+        except KeyboardInterrupt:
+            raise
+        except:
+            try:
+                # all still in an except block so we catch
+                # getattr raising
+                name = getattr(value, '__name__', None)
+                if name:
+                    # ick, recursion
+                    return text_repr(name)
+                klass = getattr(value, '__class__', None)
+                if klass:
+                    return '%s instance' % text_repr(klass)
+            except KeyboardInterrupt:
+                raise
+            except:
+                return 'UNRECOVERABLE REPR FAILURE'
+
+
+def eqrepr(value, repr=text_repr):
+    return '=%s' % repr(value)
+
+
+def nullrepr(value, repr=text_repr):
+    return ''
+
+
 #----------------------------------------------------------------------------
+
 # module testing (minimal)
 if __name__ == "__main__":
     def spam(c, d_e):

IPython/nbconvert/preprocessors/tests/files/Skip Exceptions.ipynb

@@ -1,6 +1,7 b''
 {
  "metadata": {
-  "name": ""
+  "name": "",
+  "signature": "sha256:9d47889f0678e9685429071216d0f3354db59bb66489f3225bcadfb6a1a9bbba"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -21,7 +22,8 b''
        "evalue": "message",
        "output_type": "pyerr",
        "traceback": [
-        "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m\n\u001b[1;31mException\u001b[0m                                 Traceback (most recent call last)",
+        "\u001b[1;31m---------------------------------------------------------------------------\u001b[0m",
+        "\u001b[1;31mException\u001b[0m                                 Traceback (most recent call last)",
         "\u001b[1;32m<ipython-input-1-335814d14fc1>\u001b[0m in \u001b[0;36m<module>\u001b[1;34m()\u001b[0m\n\u001b[1;32m----> 1\u001b[1;33m \u001b[1;32mraise\u001b[0m \u001b[0mException\u001b[0m\u001b[1;33m(\u001b[0m\u001b[1;34m\"message\"\u001b[0m\u001b[1;33m)\u001b[0m\u001b[1;33m\u001b[0m\u001b[0m\n\u001b[0m",
         "\u001b[1;31mException\u001b[0m: message"
        ]