Return False from isValidFont for a missing font (#156)

pyfiglet/__init__.py

@@ -179,16 +179,19 @@ def isValidFont(cls, font:str):
         if not font.endswith(('.flf', '.tlf')):
             return False
         f = None
-        if os.path.isfile(font):
-            f = open(font, 'rb')
-        else:
-            for location in FONT_DIRECTORIES:
-                full_file = os.path.join(location, font)
-                if os.path.isfile(full_file):
-                    f = open(full_file, 'rb')
-                    break
+        try:
+            if os.path.isfile(font):
+                f = open(font, 'rb')
             else:
-                f = importlib.resources.files('pyfiglet.fonts').joinpath(font).open('rb')
+                for location in FONT_DIRECTORIES:
+                    full_file = os.path.join(location, font)
+                    if os.path.isfile(full_file):
+                        f = open(full_file, 'rb')
+                        break
+                else:
+                    f = importlib.resources.files('pyfiglet.fonts').joinpath(font).open('rb')
+        except FileNotFoundError:
+            return False
 
         if zipfile.is_zipfile(f):
             # If we have a match, the ZIP file spec says we should just read the first file in the ZIP.

pyfiglet/tests/test_cli.py

@@ -55,6 +55,15 @@ def test_font_directories_are_searched(test_font_dir, monkeypatch):
     assert "0000000000" in rendered
 
 
+def test_is_valid_font_missing():
+    # A .flf/.tlf-named font that does not exist must be reported invalid,
+    # not raise FileNotFoundError. See #156.
+    assert pyfiglet.FigletFont.isValidFont("does_not_exist.flf") is False
+    assert pyfiglet.FigletFont.isValidFont("does_not_exist.tlf") is False
+    # A real bundled font is still recognized as valid.
+    assert pyfiglet.FigletFont.isValidFont("standard.flf")
+
+
 # normalize is just strip with padding
 def test_normalize():
     command = "pyfiglet -f slant -n 0"