Implement PEP570

astor/code_gen.py

@@ -240,8 +240,15 @@ class SourceGenerator(ExplicitNodeVisitor):
                 self.write(write_comma, arg)
                 self.conditional_write('=', default)
 
-        loop_args(node.args, node.defaults)
-        self.conditional_write(write_comma, '*', node.vararg)
+        posonlyargs = getattr(node, "posonlyargs", [])
+        offset = 0
+        if posonlyargs:
+            offset += len(node.defaults) - len(node.args)
+            loop_args(posonlyargs, node.defaults[:offset])
+            self.write(write_comma, "/")
+
+        loop_args(node.args, node.defaults[offset:])
+        self.conditional_write(write_comma, "*", node.vararg)
 
         kwonlyargs = self.get_kwonlyargs(node)
         if kwonlyargs:

docs/changelog.rst

@@ -27,6 +27,12 @@ New features
 .. _`Issue 138`: https://github.com/berkerpeksag/astor/issues/138
 .. _`PR 139`: https://github.com/berkerpeksag/astor/pull/139
 
+* Support Python3.8's positional only arguments.
+  (Reported and fixed by Batuhan Taskaya in `Issue 142`_ and `PR 143`_.)
+
+.. _`Issue 138`: https://github.com/berkerpeksag/astor/issues/142
+.. _`PR 139`: https://github.com/berkerpeksag/astor/pull/143
+
 Bug fixes
 ~~~~~~~~~
 

tests/test_code_gen.py

@@ -164,6 +164,23 @@ class CodegenTestCase(unittest.TestCase, Comparisons):
                 pass"""
         self.assertSrcRoundtrips(source)
 
+    @unittest.skipUnless(sys.version_info >= (3, 8, 0, "alpha", 4),
+                         "positional only arguments introduced in Python 3.8")
+    def test_pos_only_arguments(self):
+        source = """
+        def test(a, b, /, c, *, d, **kwargs):
+            pass
+
+
+        def test(a=3, b=4, /, c=7):
+            pass
+
+
+        def test(a, b=4, /, c=8, d=9):
+            pass
+        """
+        self.assertSrcRoundtrips(source)
+
     def test_pass_arguments_node(self):
         source = canonical("""
             j = [1, 2, 3]