Add config file support for config resolution

packages/smithy-aws-core/src/smithy_aws_core/config/__init__.py

@@ -0,0 +1,76 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+import os
+
+from smithy_aws_core.config.file_parser import (
+    FileType,
+    parse_config_file,
+    standardize,
+)
+from smithy_aws_core.config.parsed_config_file import ParsedConfigFile
+
+_DEFAULT_CONFIG_FILE = "~/.aws/config"
+_DEFAULT_CREDENTIALS_FILE = "~/.aws/credentials"
+_CONFIG_FILE_ENV_VAR = "AWS_CONFIG_FILE"
+_CREDENTIALS_FILE_ENV_VAR = "AWS_SHARED_CREDENTIALS_FILE"
+
+
+def resolve_config_paths(
+    config_file_path: str | None = None,
+    credentials_file_path: str | None = None,
+) -> tuple[str, str]:
+    """Resolve the final config and credentials file paths.
+
+    Resolution order for each path:
+    1. Explicit argument (if provided)
+    2. Environment variable (AWS_CONFIG_FILE / AWS_SHARED_CREDENTIALS_FILE)
+    3. Default (~/.aws/config / ~/.aws/credentials)
+
+    The ~ is expanded to the user's home directory.
+
+    :param config_file_path: Override path for config file.
+    :param credentials_file_path: Override path for credentials file.
+    :returns: Tuple of (resolved_config_path, resolved_credentials_path).
+    """
+    config_path = (
+        config_file_path or os.environ.get(_CONFIG_FILE_ENV_VAR) or _DEFAULT_CONFIG_FILE
+    )
+    credentials_path = (
+        credentials_file_path
+        or os.environ.get(_CREDENTIALS_FILE_ENV_VAR)
+        or _DEFAULT_CREDENTIALS_FILE
+    )
+
+    return (
+        os.path.expanduser(os.path.expandvars(config_path)),
+        os.path.expanduser(os.path.expandvars(credentials_path)),
+    )
+
+
+async def load_config(
+    config_file_path: str | None = None,
+    credentials_file_path: str | None = None,
+) -> ParsedConfigFile:
+    """Load and merge AWS config and credentials files.
+
+    Parses both files, standardizes them, and returns a merged
+    ParsedConfigFile ready for querying.
+
+    :param config_file_path: Override path for config file.
+        Defaults to AWS_CONFIG_FILE env var or ~/.aws/config.
+    :param credentials_file_path: Override path for credentials file.
+        Defaults to AWS_SHARED_CREDENTIALS_FILE env var or ~/.aws/credentials.
+    :returns: A ParsedConfigFile with merged profiles from both files.
+    """
+    config_path, credentials_path = resolve_config_paths(
+        config_file_path, credentials_file_path
+    )
+
+    raw_config = await parse_config_file(config_path)
+    raw_credentials = await parse_config_file(credentials_path)
+
+    std_config = standardize(raw_config, FileType.CONFIG)
+    std_credentials = standardize(raw_credentials, FileType.CREDENTIALS)
+
+    return ParsedConfigFile(std_config, std_credentials)

packages/smithy-aws-core/src/smithy_aws_core/config/exceptions.py

@@ -0,0 +1,8 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""Config related exceptions"""
+
+
+class ConfigParseError(Exception):
+    """Raised when a config file cannot be parsed due to invalid syntax."""