Catch AttributeErrors thrown by ipython_genutils during conversion as ValidationErrors (#240)

* Catch AttributeErrors thrown by ipython_genutils during reading and conversion as ValidationErrors

* fix docstrings

* revert changes to reader and extra test files, update error message

* fix test_nbformat

Author: therzka

nbformat/converter.py

@@ -5,6 +5,7 @@
 
 from . import versions
 from .reader import get_version
+from .validator import ValidationError
 
 
 def convert(nb, to_version):
@@ -20,6 +21,17 @@ def convert(nb, to_version):
     to_version : int
         Major revision to convert the notebook to.  Can either be an upgrade or
         a downgrade.
+
+    Raises
+    ------
+    ValueError
+        Notebook failed to convert.
+
+    ValueError
+        The version specified is invalid or doesn't exist.
+
+    ValidationError
+        Conversion failed due to missing expected attributes.
     """
 
     # Get input notebook version.
@@ -42,10 +54,13 @@ def convert(nb, to_version):
             step_version = version - 1
             convert_function = versions[version].downgrade
 
-        # Convert and make sure version changed during conversion.
-        converted = convert_function(nb)
-        if converted.get('nbformat', 1) == version:
-            raise ValueError("Failed to convert notebook from v%d to v%d." % (version, step_version))
+        try:
+            # Convert and make sure version changed during conversion.
+            converted = convert_function(nb)
+            if converted.get('nbformat', 1) == version:
+                raise ValueError("Failed to convert notebook from v%d to v%d." % (version, step_version))
+        except AttributeError as e:
+            raise ValidationError(f"Notebook could not be converted from version {version} to version {step_version} because it's missing a key: {e}")
 
         # Recursively convert until target version is reached.
         return convert(converted, to_version)

nbformat/tests/test3_no_metadata.ipynb

@@ -0,0 +1,147 @@
+{
+ "nbformat": 3,
+ "nbformat_minor": 0,
+ "worksheets": [
+  {
+   "cells": [
+    {
+     "cell_type": "heading",
+     "level": 1,
+     "metadata": {},
+     "source": [
+      "nbconvert latex test"
+     ]
+    },
+    {
+     "cell_type": "markdown",
+     "metadata": {},
+     "source": [
+      "**Lorem ipsum** dolor sit amet, consectetur adipiscing elit. Nunc luctus bibendum felis dictum sodales. Ut suscipit, orci ut interdum imperdiet, purus ligula mollis *justo*, non malesuada nisl augue eget lorem. Donec bibendum, erat sit amet porttitor aliquam, urna lorem ornare libero, in vehicula diam diam ut ante. Nam non urna rhoncus, accumsan elit sit amet, mollis tellus. Vestibulum nec tellus metus. Vestibulum tempor, ligula et vehicula rhoncus, sapien turpis faucibus lorem, id dapibus turpis mauris ac orci. Sed volutpat vestibulum venenatis."
+     ]
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Printed Using Python"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "print(\"hello\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "output_type": "stream",
+       "stream": "stdout",
+       "text": [
+        "hello\n"
+       ]
+      }
+     ],
+     "prompt_number": 1
+    },
+    {
+     "cell_type": "heading",
+     "level": 2,
+     "metadata": {},
+     "source": [
+      "Pyout"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "from IPython.display import HTML\n",
+      "HTML(\"\"\"\n",
+      "<script>\n",
+      "console.log(\"hello\");\n",
+      "</script>\n",
+      "<b>HTML</b>\n",
+      "\"\"\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "html": [
+        "\n",
+        "<script>\n",
+        "console.log(\"hello\");\n",
+        "</script>\n",
+        "<b>HTML</b>\n"
+       ],
+       "metadata": {},
+       "output_type": "pyout",
+       "prompt_number": 3,
+       "text": [
+        "<IPython.core.display.HTML at 0x1112757d0>"
+       ]
+      }
+     ],
+     "prompt_number": 3
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "%%javascript\n",
+      "console.log(\"hi\");"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "javascript": [
+        "console.log(\"hi\");"
+       ],
+       "metadata": {},
+       "output_type": "display_data",
+       "text": [
+        "<IPython.core.display.Javascript at 0x1112b4b50>"
+       ]
+      }
+     ],
+     "prompt_number": 7
+    },
+    {
+     "cell_type": "heading",
+     "level": 3,
+     "metadata": {},
+     "source": [
+      "Image"
+     ]
+    },
+    {
+     "cell_type": "code",
+     "collapsed": false,
+     "input": [
+      "from IPython.display import Image\n",
+      "Image(\"http://ipython.org/_static/IPy_header.png\")"
+     ],
+     "language": "python",
+     "metadata": {},
+     "outputs": [
+      {
+       "metadata": {},
+       "output_type": "pyout",
+       "png": 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L0amUWggcqrXO8gg2FKHG2CdW4Uem9XvBlUflu7RUaiByU3lPa92ZKN8cSav8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\nHMRRca/E5hVINNIVwI2B56z6/3ExLRI31pXNAAAAAElFTkSuQmCC\n",
+       "prompt_number": 6,
+       "text": [
+        "<IPython.core.display.Image at 0x111275490>"
+       ]
+      }
+     ],
+     "prompt_number": 6
+    }
+   ],
+   "metadata": {}
+  }
+ ]
+}

nbformat/tests/test_convert.py

@@ -7,7 +7,7 @@
 
 from ..converter import convert
 from ..reader import read, get_version
-from ..validator import isvalid, validate
+from ..validator import isvalid, validate, ValidationError
 from .. import current_nbformat
 
 
@@ -51,6 +51,14 @@ def test_upgrade_downgrade_4_3_4(self):
         self.assertEqual(isvalid(nb), True)
 
 
+    def test_upgrade_3_4__missing_metadata(self):
+        with self.fopen(u'test3_no_metadata.ipynb', u'r') as f:
+            nb = read(f)
+
+        with self.assertRaisesRegex(ValidationError, r'could not be converted.+metadata'):
+            convert(nb, 4)
+
+
     def test_open_current(self):
         """Can an old notebook be opened and converted to the current version
         while remembering the original version of the notebook?"""

nbformat/tests/test_nbformat.py

@@ -1,13 +1,14 @@
 import pytest
 
 from nbformat import read
+from ..validator import ValidationError
 
 
 def test_read_invalid_iowrapper(tmpdir):
     ipynb_filepath = tmpdir.join("empty.ipynb")
     ipynb_filepath.write("{}")
 
-    with pytest.raises(AttributeError) as excinfo:
+    with pytest.raises(ValidationError) as excinfo:
         with ipynb_filepath.open() as fp:
             read(fp, as_version=4)
     assert "cells" in str(excinfo.value)
@@ -17,7 +18,7 @@ def test_read_invalid_filepath(tmpdir):
     ipynb_filepath = tmpdir.join("empty.ipynb")
     ipynb_filepath.write("{}")
 
-    with pytest.raises(AttributeError) as excinfo:
+    with pytest.raises(ValidationError) as excinfo:
         read(str(ipynb_filepath), as_version=4)
     assert "cells" in str(excinfo.value)
 
@@ -26,7 +27,7 @@ def test_read_invalid_pathlikeobj(tmpdir):
     ipynb_filepath = tmpdir.join("empty.ipynb")
     ipynb_filepath.write("{}")
 
-    with pytest.raises(AttributeError) as excinfo:
+    with pytest.raises(ValidationError) as excinfo:
         read(ipynb_filepath, as_version=4)
     assert "cells" in str(excinfo.value)