Improve error message for duplicate profile sections in config

.changes/next-release/config-duplicate-profile-error.json

@@ -0,0 +1,7 @@
+[
+  {
+    "type": "bugfix",
+    "category": "config",
+    "description": "Improved error message when config file contains duplicate profile sections to include the profile name and file path"
+  }
+]

awscli/botocore/configloader.py

@@ -146,6 +146,14 @@ def raw_config_parse(config_filename, parse_subsections=True):
         cp = configparser.RawConfigParser()
         try:
             cp.read([path])
+        except configparser.DuplicateSectionError as e:
+            message = _get_duplicate_section_error_message(
+                path, e.section, e.lineno
+            )
+            raise botocore.exceptions.ConfigParseError(
+                path=_unicode_path(path),
+                message=message,
+            )
         except (configparser.Error, UnicodeDecodeError):
             raise botocore.exceptions.ConfigParseError(
                 path=_unicode_path(path)
@@ -200,6 +208,52 @@ def _parse_nested(config_value):
     return parsed
 
 
+def _find_first_section_line(path, section):
+    try:
+        with open(path, 'r', encoding='utf-8-sig', errors='replace') as f:
+            for lineno, line in enumerate(f, start=1):
+                clean_line = line.strip()
+                if not clean_line or clean_line.startswith(('#', ';')):
+                    continue
+                match = configparser.RawConfigParser.SECTCRE.match(clean_line)
+                if match:
+                    header = match.group('header')
+                    if header == section or header.strip() == section.strip():
+                        return lineno
+    except Exception:
+        pass
+    return None
+
+
+def _get_duplicate_section_error_message(path, section, dup_lineno):
+    parts = section.split(None, 1)
+    if len(parts) == 2 and parts[0] == 'profile':
+        target_type = 'profile'
+        target_name = parts[1].strip('"\'')
+    elif section == 'default':
+        target_type = 'profile'
+        target_name = 'default'
+    else:
+        target_type = 'section'
+        target_name = section
+
+    first_lineno = _find_first_section_line(path, section)
+
+    if first_lineno and dup_lineno and first_lineno != dup_lineno:
+        line_info = (
+            f" (first seen on line {first_lineno}, "
+            f"duplicated on line {dup_lineno})"
+        )
+    elif dup_lineno:
+        line_info = f" (duplicated on line {dup_lineno})"
+    elif first_lineno:
+        line_info = f" (line {first_lineno})"
+    else:
+        line_info = ""
+
+    return f"Found duplicate {target_type} '{target_name}'{line_info}"
+
+
 def _parse_section(key, values):
     result = {}
     try:

awscli/botocore/exceptions.py

@@ -299,6 +299,11 @@ class ConfigParseError(BotoCoreError):
 
     fmt = 'Unable to parse config file: {path}'
 
+    def __init__(self, **kwargs):
+        if 'message' in kwargs:
+            self.fmt = 'Unable to parse config file: {path} - {message}'
+        super().__init__(**kwargs)
+
 
 class ConfigNotFound(BotoCoreError):
     """

tests/unit/botocore/test_configloader.py

@@ -207,6 +207,97 @@ def test_services_config(self):
             'https://localhost:8888/',
         )
 
+    def test_duplicate_profile_error_message(self):
+        contents = (
+            '[default]\n'
+            'region = us-west-2\n\n'
+            '[profile xyz]\n'
+            'aws_access_key_id = foo\n'
+            'aws_secret_access_key = bar\n\n'
+            '[profile other]\n'
+            'region = eu-west-1\n\n'
+            '[profile xyz]\n'
+            'aws_access_key_id = baz\n'
+        )
+        full_path = os.path.join(self.tempdir, 'aws_config_dup_profile')
+        with open(full_path, 'w') as f:
+            f.write(contents)
+
+        with self.assertRaises(botocore.exceptions.ConfigParseError) as cm:
+            raw_config_parse(full_path)
+        expected_msg = (
+            f"Unable to parse config file: {full_path} - "
+            "Found duplicate profile 'xyz' "
+            "(first seen on line 4, duplicated on line 11)"
+        )
+        self.assertEqual(str(cm.exception), expected_msg)
+
+        # Also verify load_config raises the same error
+        with self.assertRaises(botocore.exceptions.ConfigParseError) as cm:
+            load_config(full_path)
+        self.assertEqual(str(cm.exception), expected_msg)
+
+    def test_duplicate_profile_with_quotes_error_message(self):
+        contents = (
+            '[profile "personal"]\n'
+            'aws_access_key_id = foo\n'
+            'aws_secret_access_key = bar\n\n'
+            '[profile "personal"]\n'
+            'aws_access_key_id = baz\n'
+        )
+        full_path = os.path.join(self.tempdir, 'aws_config_dup_quotes')
+        with open(full_path, 'w') as f:
+            f.write(contents)
+
+        with self.assertRaises(botocore.exceptions.ConfigParseError) as cm:
+            raw_config_parse(full_path)
+        expected_msg = (
+            f"Unable to parse config file: {full_path} - "
+            "Found duplicate profile 'personal' "
+            "(first seen on line 1, duplicated on line 5)"
+        )
+        self.assertEqual(str(cm.exception), expected_msg)
+
+    def test_duplicate_default_profile_error_message(self):
+        contents = (
+            '[default]\n'
+            'region = us-west-2\n\n'
+            '[default]\n'
+            'region = us-east-1\n'
+        )
+        full_path = os.path.join(self.tempdir, 'aws_config_dup_default')
+        with open(full_path, 'w') as f:
+            f.write(contents)
+
+        with self.assertRaises(botocore.exceptions.ConfigParseError) as cm:
+            raw_config_parse(full_path)
+        expected_msg = (
+            f"Unable to parse config file: {full_path} - "
+            "Found duplicate profile 'default' "
+            "(first seen on line 1, duplicated on line 4)"
+        )
+        self.assertEqual(str(cm.exception), expected_msg)
+
+    def test_duplicate_section_error_message(self):
+        contents = (
+            '[sso-session my-session]\n'
+            'sso_region = us-west-2\n\n'
+            '[sso-session my-session]\n'
+            'sso_region = us-east-1\n'
+        )
+        full_path = os.path.join(self.tempdir, 'aws_config_dup_section')
+        with open(full_path, 'w') as f:
+            f.write(contents)
+
+        with self.assertRaises(botocore.exceptions.ConfigParseError) as cm:
+            raw_config_parse(full_path)
+        expected_msg = (
+            f"Unable to parse config file: {full_path} - "
+            "Found duplicate section 'sso-session my-session' "
+            "(first seen on line 1, duplicated on line 4)"
+        )
+        self.assertEqual(str(cm.exception), expected_msg)
+
 
 if __name__ == "__main__":
     unittest.main()

tests/unit/botocore/test_exceptions.py

@@ -98,6 +98,21 @@ def test_single_kwarg_botocore_error(self):
         self.assertEqual(str(unpickled_exception), str(exception))
         self.assertEqual(unpickled_exception.kwargs, exception.kwargs)
 
+    def test_config_parse_error(self):
+        exception = botocore.exceptions.ConfigParseError(
+            path='/path/to/config',
+            message=(
+                "Found duplicate profile 'xyz' "
+                "(first seen on line 5, duplicated on line 20)"
+            ),
+        )
+        unpickled_exception = pickle.loads(pickle.dumps(exception))
+        self.assertIsInstance(
+            unpickled_exception, botocore.exceptions.ConfigParseError
+        )
+        self.assertEqual(str(unpickled_exception), str(exception))
+        self.assertEqual(unpickled_exception.kwargs, exception.kwargs)
+
     def test_multiple_kwarg_botocore_error(self):
         exception = botocore.exceptions.UnknownServiceError(
             service_name='myservice', known_service_names=['s3']