Add support for f-string debugging syntax (#139)

Fixes #138

astor/code_gen.py

@@ -584,7 +584,11 @@ class SourceGenerator(ExplicitNodeVisitor):
                         self.write(value.s.replace('{', '{{').replace('}', '}}'))
                     elif isinstance(value, ast.FormattedValue):
                         with self.delimit('{}'):
-                            self.visit(value.value)
+                            # expr_text used for f-string debugging syntax.
+                            if getattr(value, 'expr_text', None):
+                                self.write(value.expr_text)
+                            else:
+                                self.visit(value.value)
                             if value.conversion != -1:
                                 self.write('!%s' % chr(value.conversion))
                             if value.format_spec is not None:

docs/changelog.rst

@@ -21,6 +21,12 @@ New features
 .. _`Issue 126`: https://github.com/berkerpeksag/astor/issues/126
 .. _`PR 134`: https://github.com/berkerpeksag/astor/pull/134
 
+* Support Python 3.8's f-string debugging syntax.
+  (Reported and fixed by Batuhan Taskaya in `Issue 138`_ and `PR 139`_.)
+
+.. _`Issue 138`: https://github.com/berkerpeksag/astor/issues/138
+.. _`PR 139`: https://github.com/berkerpeksag/astor/pull/139
+
 Bug fixes
 ~~~~~~~~~
 

tests/test_code_gen.py

+# coding: utf-8
 """
 Part of the astor library for Python AST manipulation
 
@@ -664,6 +665,19 @@ class CodegenTestCase(unittest.TestCase, Comparisons):
         '''
         self.assertSrcRoundtripsGtVer(source, (3, 6))
 
+    @unittest.skipUnless(sys.version_info >= (3, 8, 0, "alpha", 4),
+                         "f-string debugging introduced in Python 3.8")
+    def test_fstring_debugging(self):
+        source = """
+        x = f'{5=}'
+        y = f'{5=!r}'
+        z = f'{3*x+15=}'
+        f'{x=:}'
+        f'{x=:.2f}'
+        f'alpha α {pi=} ω omega'
+        """
+        self.assertAstRoundtripsGtVer(source, (3, 8))
+
     def test_docstring_function(self):
         source = '''
         def f(arg):