don't use sys.exit(...) inside main(), but only under if __name__ == "__main__"

The convention is that sys.exit(...) is called only if a module is run as a script,
and that main() entry points use return statements to report exit codes: 0 (or None)
for successful execution, or any non-zero integer for errors.

E.g. see the console scripts generated when installing with pip.

Lib/fontTools/__main__.py

@@ -1,7 +1,8 @@
 from __future__ import print_function, division, absolute_import
+import sys
+
 
 def main(args=None):
-	import sys
 	if args is None:
 		args = sys.argv[1:]
 
@@ -27,5 +28,6 @@ def main(args=None):
 	import runpy
 	runpy.run_module(mod, run_name='__main__')
 
+
 if __name__ == '__main__':
-	main()
+	sys.exit(main())

Lib/fontTools/inspect.py

@@ -262,10 +262,10 @@ def main(args=None):
 		args = sys.argv[1:]
 	if len(args) < 1:
 		print("usage: pyftinspect font...", file=sys.stderr)
-		sys.exit(1)
+		return 1
 	for arg in args:
 		Inspect(arg)
 	gtk.main()
 
 if __name__ == "__main__":
-	main()
+	sys.exit(main())

Lib/fontTools/merge.py

@@ -932,7 +932,7 @@ def main(args=None):
 
 	if len(args) < 1:
 		print("usage: pyftmerge font...", file=sys.stderr)
-		sys.exit(1)
+		return 1
 
 	configLogger(level=logging.INFO if options.verbose else logging.WARNING)
 	if options.timing:
@@ -948,4 +948,4 @@ def main(args=None):
 
 
 if __name__ == "__main__":
-	main()
+	sys.exit(main())

Lib/fontTools/mtiLib/__init__.py

@@ -1151,11 +1151,14 @@ def build(f, font, tableTag=None):
 	return parseTable(lines, font, tableTag=tableTag)
 
 
-def main(args, font=None):
+def main(args=None, font=None):
 	import sys
 	from fontTools import configLogger
 	from fontTools.misc.testTools import MockFont
 
+	if args is None:
+		args = sys.argv[1:]
+
 	# configure the library logger (for >= WARNING)
 	configLogger()
 	# comment this out to enable debug messages from mtiLib's logger
@@ -1186,6 +1189,7 @@ def main(args, font=None):
 		writer.endtag(tag)
 		writer.newline()
 
+
 if __name__ == '__main__':
 	import sys
-	main (sys.argv[1:])
+	sys.exit(main())

Lib/fontTools/subset/__init__.py

@@ -2872,7 +2872,7 @@ def main(args=None):
 
     if '--help' in args:
         print(__doc__)
-        sys.exit(0)
+        return 0
 
     options = Options()
     try:
@@ -2885,11 +2885,11 @@ def main(args=None):
     except options.OptionError as e:
         usage()
         print("ERROR:", e, file=sys.stderr)
-        sys.exit(2)
+        return 2
 
     if len(args) < 2:
         usage()
-        sys.exit(1)
+        return 1
 
     configLogger(level=logging.INFO if options.verbose else logging.WARNING)
     if options.timing:
@@ -2995,4 +2995,4 @@ __all__ = [
 ]
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

Lib/fontTools/subset/__main__.py

@@ -1,6 +1,7 @@
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
+import sys
 from fontTools.subset import main
 
 if __name__ == '__main__':
-	main()
+    sys.exit(main())

Lib/fontTools/ttx.py

@@ -414,4 +414,4 @@ def main(args=None):
 
 
 if __name__ == "__main__":
-	main()
+	sys.exit(main())

Lib/fontTools/varLib/__init__.py

@@ -449,7 +449,6 @@ def main(args=None):
 if __name__ == "__main__":
 	import sys
 	if len(sys.argv) > 1:
-		main()
-		#sys.exit(0)
+		sys.exit(main())
 	import doctest, sys
 	sys.exit(doctest.testmod().failed)

Lib/fontTools/varLib/__main__.py

@@ -1,6 +1,7 @@
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
+import sys
 from fontTools.varLib import main
 
 if __name__ == '__main__':
-	main()
+	sys.exit(main())

Lib/fontTools/varLib/interpolate_layout.py

@@ -337,7 +337,6 @@ def main(args=None):
 if __name__ == "__main__":
 	import sys
 	if len(sys.argv) > 1:
-		main()
-		#sys.exit(0)
+		sys.exit(main())
 	import doctest, sys
 	sys.exit(doctest.testmod().failed)

Lib/fontTools/varLib/mutator.py

@@ -60,7 +60,6 @@ def main(args=None):
 if __name__ == "__main__":
 	import sys
 	if len(sys.argv) > 1:
-		main()
-		#sys.exit(0)
+		sys.exit(main())
 	import doctest, sys
 	sys.exit(doctest.testmod().failed)

Snippets/interpolate.py

@@ -140,4 +140,5 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    import sys
+    sys.exit(main())

Snippets/woff2_compress.py

@@ -13,7 +13,7 @@ def main(args=None):
         args = sys.argv[1:]
     if len(args) < 1:
         print("One argument, the input filename, must be provided.", file=sys.stderr)
-        sys.exit(1)
+        return 1
 
     filename = args[0]
     outfilename = makeOutputFileName(filename, outputDir=None, extension='.woff2')
@@ -26,4 +26,4 @@ def main(args=None):
 
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

Snippets/woff2_decompress.py

@@ -23,7 +23,7 @@ def main(args=None):
         args = sys.argv[1:]
     if len(args) < 1:
         print("One argument, the input filename, must be provided.", file=sys.stderr)
-        sys.exit(1)
+        return 1
 
     filename = args[0]
     outfilename = make_output_name(filename)
@@ -36,4 +36,4 @@ def main(args=None):
 
 
 if __name__ == '__main__':
-    main()
+    sys.exit(main())

fonttools

@@ -9,5 +9,4 @@ sys.path.insert(0, libdir)
 from fontTools.__main__ import main
 
 if __name__ == '__main__':
-
-	main()
+	sys.exit(main())