Handle empty sections when using configure set command

awscli/customizations/configure/writer.py

@@ -108,11 +108,17 @@ def _update_section_contents(self, contents, section_name, new_values):
         # to figure out if we're updating a value or adding a new value.
         # There's 2 cases.  Either we're setting a normal scalar value
         # of, we're setting a nested value.
-        section_start_line_num += 1
         last_matching_line = section_start_line_num
-        j = section_start_line_num
+        j = last_matching_line + 1
         while j < len(contents):
             line = contents[j]
+            if self.SECTION_REGEX.search(line) is not None:
+                # We've hit a new section which means the config key is
+                # not in the section.  We need to add it here.
+                self._insert_new_values(line_number=last_matching_line,
+                                        contents=contents,
+                                        new_values=new_values)
+                return
             match = self.OPTION_REGEX.search(line)
             if match is not None:
                 last_matching_line = j
@@ -131,13 +137,6 @@ def _update_section_contents(self, contents, section_name, new_values):
                             j, contents, new_values[key_name],
                             len(match.group(1)) - len(match.group(1).lstrip()))
                         return
-            elif self.SECTION_REGEX.search(line) is not None:
-                # We've hit a new section which means the config key is
-                # not in the section.  We need to add it here.
-                self._insert_new_values(line_number=last_matching_line,
-                                        contents=contents,
-                                        new_values=new_values)
-                return
             j += 1
 
         if new_values:

tests/integration/customizations/test_configure.py

@@ -298,6 +298,22 @@ def test_get_nested_attribute(self):
         self.assertEqual(p.rc, 1)
         self.assertEqual(p.stdout, '')
 
+    def test_can_handle_empty_section(self):
+        self.set_config_file_contents(
+            '[default]\n'
+        )
+        p = aws('configure set preview.cloudfront true',
+                env_vars=self.env_vars)
+        p = aws('configure set region us-west-2',
+                env_vars=self.env_vars)
+        self.assertEqual(
+            '[default]\n'
+            'region = us-west-2\n'
+            '[preview]\n'
+            'cloudfront = true\n',
+            self.get_config_file_contents(),
+        )
+
 
 class TestConfigureHasArgTable(unittest.TestCase):
     def test_configure_command_has_arg_table(self):

tests/unit/customizations/configure/test_writer.py

@@ -335,4 +335,18 @@ def test_update_nested_attr_no_prior_nesting(self):
             's3 =\n'
             '    signature_version = newval\n'
             '[profile foo]\n'
-            'foo = bar\n')
+            'foo = bar\n')
+
+    def test_can_handle_empty_section(self):
+        original = (
+            '[default]\n'
+            '[preview]\n'
+            'cloudfront = true\n'
+        )
+        self.assert_update_config(
+            original, {'region': 'us-west-2', '__section__': 'default'},
+            '[default]\n'
+            'region = us-west-2\n'
+            '[preview]\n'
+            'cloudfront = true\n'
+        )