Honor 'Date': None in metadata

yuyichao · yuyichao · commit 2b44dbb49e4f · 2020-07-19T03:04:24.000-04:00
Allow removing the 'Date' metadata from output. Fix #17968
diff --git a/lib/matplotlib/backends/backend_svg.py b/lib/matplotlib/backends/backend_svg.py
@@ -338,7 +338,10 @@ def _write_metadata(self, metadata):
 
         # Special handling.
         date = metadata.get('Date', None)
-        if date is not None:
+        if date is None and 'Date' in metadata:
+            # User explicitly set `Date` to `None`
+            pass
+        elif date is not None:
             if isinstance(date, str):
                 dates = [date]
             elif isinstance(date, (datetime.datetime, datetime.date)):
diff --git a/lib/matplotlib/tests/test_backend_svg.py b/lib/matplotlib/tests/test_backend_svg.py
@@ -371,6 +371,20 @@ def test_svg_default_metadata(monkeypatch):
     # Type
     assert 'StillImage' in buf
 
+    # Now make sure all the default metadata can be cleared.
+    with BytesIO() as fd:
+        fig.savefig(fd, format='svg', metadata={'Date': None, 'Creator': None,
+                                                'Format': None, 'Type': None})
+        buf = fd.getvalue().decode()
+
+    # Creator
+    assert mpl.__version__ not in buf
+    # Date
+    assert '1970-08-16' not in buf
+    # Format
+    assert 'image/svg+xml' not in buf
+    # Type
+    assert 'StillImage' not in buf
 
 def test_svg_metadata():
     single_value = ['Coverage', 'Identifier', 'Language', 'Relation', 'Source',
