Merge pull request matplotlib#18825 from anntzer/pgffontwarn

Warn in pgf backend when unknown font is requested.

Author: QuLogic

lib/matplotlib/backends/backend_pgf.py

@@ -134,7 +134,7 @@ def _font_properties_str(prop):
           and mpl.rcParams["pgf.texsystem"] != "pdflatex"):
         commands.append(r"\setmainfont{%s}\rmfamily" % family)
     else:
-        pass  # print warning?
+        _log.warning("Ignoring unknown font: %s", family)
 
     size = prop.get_size_in_points()
     commands.append(r"\fontsize{%f}{%f}" % (size, size * 1.2))

lib/matplotlib/tests/test_backend_pgf.py

@@ -328,3 +328,13 @@ def test_png():
     # Just a smoketest.
     fig, ax = plt.subplots()
     fig.savefig(BytesIO(), format="png", backend="pgf")
+
+
+@needs_xelatex
+def test_unknown_font(caplog):
+    with caplog.at_level("WARNING"):
+        mpl.rcParams["font.family"] = "this-font-does-not-exist"
+        plt.figtext(.5, .5, "hello, world")
+        plt.savefig(BytesIO(), format="pgf")
+    assert "Ignoring unknown font: this-font-does-not-exist" in [
+        r.getMessage() for r in caplog.records]