Start working on mutation issues in validate.

We change the validation logic and separate the normalisation from
the validation step.

We make sure that if a notebook is normalized, it emits a warning.
In the future we will turn the warning in to an Error.

We add test for the current and an xfail test for the future behavior

nbformat/json_compat.py

@@ -76,6 +76,12 @@ def _validator_for_name(validator_name):
     for (name, module, validator_cls) in _VALIDATOR_MAP:
         if module and validator_name == name:
             return validator_cls
+    # we always return something.
+    raise ValueError(
+        "Missing validator for {validator_name}".format(
+            validator_name=repr(validator_name)
+        )
+    )
 
 
 def get_current_validator():

nbformat/tests/test4.5.ipynb

@@ -0,0 +1,164 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "id": "2fcdfa53",
+   "metadata": {},
+   "source": [
+    "# nbconvert latex test"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "0bc81532",
+   "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": "markdown",
+   "id": "bb687f78",
+   "metadata": {},
+   "source": [
+    "## Printed Using Python"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "38f37a24",
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "hello\n"
+     ]
+    }
+   ],
+   "source": [
+    "print(\"hello\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "a1f70963",
+   "metadata": {},
+   "source": [
+    "## Pyout"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 3,
+   "id": "8206b3b9",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": [
+       "\n",
+       "<script>\n",
+       "console.log(\"hello\");\n",
+       "</script>\n",
+       "<b>HTML</b>\n"
+      ],
+      "text/plain": [
+       "<IPython.core.display.HTML at 0x1112757d0>"
+      ]
+     },
+     "execution_count": 3,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "from IPython.display import HTML\n",
+    "HTML(\"\"\"\n",
+    "<script>\n",
+    "console.log(\"hello\");\n",
+    "</script>\n",
+    "<b>HTML</b>\n",
+    "\"\"\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 7,
+   "id": "88d8965b",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "application/javascript": [
+       "console.log(\"hi\");"
+      ],
+      "text/plain": [
+       "<IPython.core.display.Javascript at 0x1112b4b50>"
+      ]
+     },
+     "metadata": {},
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "%%javascript\n",
+    "console.log(\"hi\");"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "34334c4f",
+   "metadata": {},
+   "source": [
+    "### Image"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 6,
+   "id": "8b414a68",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "image/png": 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L0amUWggcqrXO8gg2FKHG2CdW4Uem9XvBlUflu7RUaiByU3lPa92ZKN8cSav8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\nHMRRca/E5hVINNIVwI2B56z6/3ExLRI31pXNAAAAAElFTkSuQmCC\n",
+      "text/plain": [
+       "<IPython.core.display.Image at 0x111275490>"
+      ]
+     },
+     "execution_count": 6,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "from IPython.display import Image\n",
+    "Image(\"http://ipython.org/_static/IPy_header.png\")"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.10.0"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

nbformat/tests/test_validator.py

@@ -6,6 +6,9 @@
 import os
 import re
 
+from nbformat.warnings import MissingIDFieldWarning
+from copy import deepcopy
+
 from .base import TestsBase
 from jsonschema import ValidationError
 from nbformat import read
@@ -14,6 +17,8 @@
 
 import pytest
 
+nb4 = ("test4.ipynb", "test4.5.ipynb")
+
 
 # Fixtures
 @pytest.fixture(autouse=True)
@@ -29,6 +34,49 @@ def set_validator(validator_name):
     os.environ["NBFORMAT_VALIDATOR"] = validator_name
 
 
+@pytest.mark.parametrize("validator_name", VALIDATORS)
+def test_should_warn(validator_name):
+    """Test that a v4 notebook witout id emit a warning"""
+    set_validator(validator_name)
+    with TestsBase.fopen(u"test4.5.ipynb", u"r") as f:
+        nb = read(f, as_version=4)
+
+    del nb.cells[3]["id"]
+    assert nb.cells[3].get("id") is None
+    assert nb.cells[3]["cell_type"] == "code"
+
+    nb_copy = deepcopy(nb)
+
+    with pytest.warns(MissingIDFieldWarning):
+        validate(nb)
+    assert isvalid(nb) == True
+
+
+@pytest.mark.xfail(reason="In the future we want to stop warning, and raise an error")
+@pytest.mark.parametrize("validator_name", VALIDATORS)
+def test_should_not_mutate(validator_name):
+    """Test that a v4 notebook without id raise an error and does/not mutate
+
+    Probably should be 2 test. To enable in the future.
+    """
+    set_validator(validator_name)
+    with TestsBase.fopen(u"test4.5.ipynb", u"r") as f:
+        nb = read(f, as_version=4)
+
+    del nb.cells[3]["id"]
+    assert nb.cells[3].get("id") is None
+    assert nb.cells[3]["cell_type"] == "code"
+
+    nb_deep_copy = deepcopy(nb)
+
+    with (pytest.raises(MissingIDFieldWarning), pytest.warns(None)):
+        validate(nb)
+
+    assert nb == nb_deep_copy
+
+    assert isvalid(nb) == True
+
+
 @pytest.mark.parametrize("validator_name", VALIDATORS)
 def test_nb2(validator_name):
     """Test that a v2 notebook converted to current passes validation"""
@@ -50,10 +98,11 @@ def test_nb3(validator_name):
 
 
 @pytest.mark.parametrize("validator_name", VALIDATORS)
-def test_nb4(validator_name):
+@pytest.mark.parametrize("nbfile", nb4)
+def test_nb4(validator_name, nbfile):
     """Test that a v4 notebook passes validation"""
     set_validator(validator_name)
-    with TestsBase.fopen(u'test4.ipynb', u'r') as f:
+    with TestsBase.fopen(nbfile, u"r") as f:
         nb = read(f, as_version=4)
     validate(nb)
     assert isvalid(nb) == True