font-patcher: Handle argument checks with arguments

[why]
The extension handling is a bit out-of-place and could be handled by the
arguments handling, which simplifies the code.
Somes goes for other argument validity checks.

[how]
Put argument checks into setup_arguments().

Dropping self.extensions in favour of self.args.extensions.

No functional change.

Signed-off-by: Fini Jastrow <ulf.fini.jastrow@desy.de>

font-patcher

@@ -163,16 +163,8 @@ class font_patcher:
         self.patch_set = None  # class 'list'
         self.font_dim = None  # class 'dict'
         self.onlybitmaps = 0
-        self.extension = ""
         self.essential = set()
         self.config = configparser.ConfigParser(empty_lines_in_values=False, allow_no_value=True)
-        if not os.path.isfile(self.args.font):
-            sys.exit("{}: Font file does not exist: {}".format(projectName, self.args.font))
-        if not os.access(self.args.font, os.R_OK):
-            sys.exit("{}: Can not open font file for reading: {}".format(projectName, self.args.font))
-        if len(fontforge.fontsInFile(self.args.font)) > 1:
-            sys.exit("{}: Font file contains {} fonts, can only handle single font files".format(projectName,
-                len(fontforge.fontsInFile(self.args.font))))
         try:
             self.sourceFont = fontforge.open(self.args.font, 1) # 1 = ("fstypepermitted",))
         except Exception:
@@ -181,19 +173,12 @@ class font_patcher:
         self.get_essential_references()
         self.setup_name_backup()
         self.remove_ligatures()
-        make_sure_path_exists(self.args.outputdir)
         self.check_position_conflicts()
         self.setup_patch_set()
         self.setup_line_dimensions()
         self.get_sourcefont_dimensions()
         self.sourceFont.encoding = 'UnicodeFull'  # Update the font encoding to ensure that the Unicode glyphs are available
         self.onlybitmaps = self.sourceFont.onlybitmaps  # Fetch this property before adding outlines. NOTE self.onlybitmaps initialized and never used
-        if self.args.extension == "":
-            self.extension = os.path.splitext(self.args.font)[1]
-        else:
-            self.extension = '.' + self.args.extension
-        if re.match("\.ttc$", self.extension, re.IGNORECASE):
-            sys.exit(projectName + ": Can not create True Type Collections")
 
 
     def patch(self):
@@ -261,11 +246,11 @@ class font_patcher:
     def generate(self):
         # the `PfEd-comments` flag is required for Fontforge to save '.comment' and '.fontlog'.
         if self.sourceFont.fullname != None:
-            outfile = self.args.outputdir + "/" + self.sourceFont.fullname + self.extension
+            outfile = self.args.outputdir + "/" + self.sourceFont.fullname + self.args.extension
             self.sourceFont.generate(outfile, flags=(str('opentype'), str('PfEd-comments')))
             message = "\nGenerated: {} in '{}'".format(self.sourceFont.fullname, outfile)
         else:
-            outfile = self.args.outputdir + "/" + self.sourceFont.cidfontname + self.extension
+            outfile = self.args.outputdir + "/" + self.sourceFont.cidfontname + self.args.extension
             self.sourceFont.generate(outfile, flags=(str('opentype'), str('PfEd-comments')))
             message = "\nGenerated: {} in '{}'".format(self.sourceFont.fontname, outfile)
 
@@ -1270,6 +1255,22 @@ def setup_arguments():
         print("Warniung: Specified contradicting --variable-width-glyphs and --use-single-width-glyph. Ignoring --variable-width-glyphs.")
         args.nonmono = False
 
+    make_sure_path_exists(args.outputdir)
+    if not os.path.isfile(args.font):
+        sys.exit("{}: Font file does not exist: {}".format(projectName, args.font))
+    if not os.access(args.font, os.R_OK):
+        sys.exit("{}: Can not open font file for reading: {}".format(projectName, args.font))
+    if len(fontforge.fontsInFile(args.font)) > 1:
+        sys.exit("{}: Font file contains {} fonts, can only handle single font files".format(projectName,
+            len(fontforge.fontsInFile(args.font))))
+
+    if args.extension == "":
+        args.extension = os.path.splitext(args.font)[1]
+    else:
+        args.extension = '.' + args.extension
+    if re.match("\.ttc$", args.extension, re.IGNORECASE):
+        sys.exit(projectName + ": Can not create True Type Collections")
+
     return args