Fixes issue with valid Notebooks not diffing

The diffing library was not taking into account that notebook code cells
can have no output entry, and assumed there would be an empty output
entry instead, which was causing errors

Changelog: fixed

Gemfile.lock

@@ -100,7 +100,7 @@ PATH
 PATH
   remote: gems/ipynbdiff
   specs:
-    ipynbdiff (0.4.7)
+    ipynbdiff (0.4.8)
       diffy (~> 3.4)
       oj (~> 3.13.16)
 

gems/ipynbdiff/Gemfile.lock

 PATH
   remote: .
   specs:
-    ipynbdiff (0.4.7)
+    ipynbdiff (0.4.8)
       diffy (~> 3.4)
       oj (~> 3.13.16)
 

gems/ipynbdiff/lib/ipynb_diff/transformer.rb

@@ -80,6 +80,8 @@ def transform_code_cell(cell, notebook, symbol)
     end
 
     def transform_outputs(outputs, symbol)
+      return [] unless outputs
+
       transformed = outputs.map
                            .with_index { |output, i| @out_transformer.transform(output, symbol / ['outputs', i]) }
                            .compact

gems/ipynbdiff/lib/ipynb_diff/version.rb

@@ -2,6 +2,6 @@
 
 module IpynbDiff
   module Version
-    VERSION = '0.4.7'
+    VERSION = '0.4.8'
   end
 end

gems/ipynbdiff/spec/test_helper.rb

@@ -20,6 +20,10 @@ def test_case_input_path(test_case)
   File.join(BASE_PATH, test_case, 'input.ipynb')
 end
 
+def test_case_input_path_test(test_case)
+  File.join(BASE_PATH, test_case, 'input.ipynb.test')
+end
+
 def test_case_symbols_path(test_case)
   File.join(BASE_PATH, test_case, 'expected_symbols.txt')
 end
@@ -38,7 +42,8 @@ def read_file_if_exists(path)
 
 def read_test_case(test_case_name)
   {
-    input: read_file_if_exists(test_case_input_path(test_case_name)),
+    input: read_file_if_exists(test_case_input_path(test_case_name)) ||
+      read_file_if_exists(test_case_input_path_test(test_case_name)),
     expected_markdown: read_file_if_exists(test_case_md_path(test_case_name)),
     expected_symbols: read_file_if_exists(test_case_symbols_path(test_case_name)),
     expected_line_numbers: read_file_if_exists(test_case_line_numbers_path(test_case_name))

gems/ipynbdiff/spec/testdata/only_code/input.ipynb → gems/ipynbdiff/spec/testdata/only_code/input.ipynb.test

@@ -5,7 +5,6 @@
    "execution_count": 1,
    "id": "3",
    "metadata": {},
-   "outputs": [],
    "source": [
     "import pandas as pd\n",
     "import numpy as np\n",