fix(IpynbOutput)!: rank always favors output format

Previously, both `fmt == f` case and Image have a rank of 1.
In the end, e.g. from ipynb to html conversion,
if both html and image exists, it actually prefers the image.
This commit changes this, so that fmt == f is always highest rank,
and rank never collides.
This is achieved by keeping fmt == f case having rank 1,
and every other rank increased by 1.

2 files changed, 70 insertions, 0 deletions

diff --git a/test/ipynb/rank.ipynb b/test/ipynb/rank.ipynb
new file mode 100644
index 000000000..c03ed7d99
--- /dev/null
+++ b/test/ipynb/rank.ipynb
@@ -0,0 +1,60 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 1,
+   "id": "5cf8f54d-bf3c-4db2-996d-22662a86ad43",
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "import matplotlib.pyplot as plt"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 2,
+   "id": "a0228622-9ff8-4392-9ddd-f70a90f0e106",
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/html": "<p><em>you should see this when converting from ipynb to html instead of the image below.</em></p>",
+      "image/png": "iVBORw0KGgoAAAANSUhEUgAAAAQAAAAECAYAAACp8Z5+AAAAOXRFWHRTb2Z0d2FyZQBNYXRwbG90bGliIHZlcnNpb24zLjUuMCwgaHR0cHM6Ly9tYXRwbG90bGliLm9yZy8/fFQqAAAACXBIWXMAAACdAAAAnQGPcuduAAAASUlEQVR4nGNkYGBgc1HM+/lfkI/hqQ0XAwsDAwPDzSphBi6h/wwlahsgAiJCHxkkBL4zWLA8YGBkYGBgZGBg4GRgYPjDwMDABADgfgxL+wQIRAAAAABJRU5ErkJggg==\n",
+      "text/plain": [
+       "<Figure size 4x4 with 1 Axes>"
+      ]
+     },
+     "metadata": {
+      "needs_background": "light"
+     },
+     "output_type": "display_data"
+    }
+   ],
+   "source": [
+    "fig, ax = plt.subplots(figsize=(1, 1), dpi=4)\n",
+    "ax.imshow([[0, 1], [2, 3]]);"
+   ]
+  }
+ ],
+ "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
+}
diff --git a/test/ipynb/rank.out.html b/test/ipynb/rank.out.html
new file mode 100644
index 000000000..eb5176509
--- /dev/null
+++ b/test/ipynb/rank.out.html
@@ -0,0 +1,10 @@
+<div id="5cf8f54d-bf3c-4db2-996d-22662a86ad43" class="cell code" data-execution_count="1">
+<div class="sourceCode" id="cb1"><pre class="sourceCode python"><code class="sourceCode python"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="im">import</span> matplotlib.pyplot <span class="im">as</span> plt</span></code></pre></div>
+</div>
+<div id="a0228622-9ff8-4392-9ddd-f70a90f0e106" class="cell code" data-execution_count="2">
+<div class="sourceCode" id="cb2"><pre class="sourceCode python"><code class="sourceCode python"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>fig, ax <span class="op">=</span> plt.subplots(figsize<span class="op">=</span>(<span class="dv">1</span>, <span class="dv">1</span>), dpi<span class="op">=</span><span class="dv">4</span>)</span>
+<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>ax.imshow([[<span class="dv">0</span>, <span class="dv">1</span>], [<span class="dv">2</span>, <span class="dv">3</span>]])<span class="op">;</span></span></code></pre></div>
+<div class="output display_data">
+<p><em>you should see this when converting from ipynb to html instead of the image below.</em></p>
+</div>
+</div>