From 671750cca64835e384572343c919ac5f17d00075 Mon Sep 17 00:00:00 2001
From: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>
Date: Sat, 6 Apr 2019 11:23:52 +0200
Subject: [PATCH] Check for positive number or rows and cols

---
 lib/matplotlib/axes/_subplots.py    |  4 ++++
 lib/matplotlib/tests/test_figure.py | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/lib/matplotlib/axes/_subplots.py b/lib/matplotlib/axes/_subplots.py
index 001f5f1624cb..f5e57cd73326 100644
--- a/lib/matplotlib/axes/_subplots.py
+++ b/lib/matplotlib/axes/_subplots.py
@@ -48,6 +48,10 @@ def __init__(self, fig, *args, **kwargs):
             rows, cols, num = args
             rows = int(rows)
             cols = int(cols)
+            if rows <= 0:
+                raise ValueError(f'Number of rows must be > 0, not {rows}')
+            if cols <= 0:
+                raise ValueError(f'Number of columns must be > 0, not {cols}')
             if isinstance(num, tuple) and len(num) == 2:
                 num = [int(n) for n in num]
                 self._subplotspec = GridSpec(
diff --git a/lib/matplotlib/tests/test_figure.py b/lib/matplotlib/tests/test_figure.py
index 6ae4d430df01..28a0de07fe6e 100644
--- a/lib/matplotlib/tests/test_figure.py
+++ b/lib/matplotlib/tests/test_figure.py
@@ -164,6 +164,18 @@ def test_gca():
     assert fig.gca() is ax1
 
 
+def test_add_subplot_invalid():
+    fig = plt.figure()
+    with pytest.raises(ValueError):
+        fig.add_subplot(2, 0, 1)
+    with pytest.raises(ValueError):
+        fig.add_subplot(0, 2, 1)
+    with pytest.raises(ValueError):
+        fig.add_subplot(2, 2, 0)
+    with pytest.raises(ValueError):
+        fig.add_subplot(2, 2, 5)
+
+
 @image_comparison(baseline_images=['figure_suptitle'])
 def test_suptitle():
     fig, _ = plt.subplots()