feat(dashscope): support to load headers from the environment

[DavdGao]

AgentScope Version

[The version of AgentScope you are working on, e.g. import agentscope; print(agentscope.__version__)]

Description

[Please describe the background, purpose, changes made, and how to test this PR]

Checklist

Please check the following items before code is ready to be reviewed.

• Code has been formatted with pre-commit run --all-files command
• All tests are passing
• Docstrings are in Google style
• Related documentation has been updated (e.g. links, examples, etc.)
• Code is ready for review

[Copilot]

Pull request overview

This pull request adds support for loading HTTP headers from the DASHSCOPE_API_HEADERS environment variable for DashScope API calls. This allows users to configure custom headers without modifying code.

Key Changes

• Added environment variable loading for DASHSCOPE_API_HEADERS in the DashScopeChatModel initialization
• Headers from the environment variable are parsed as JSON and merged with explicitly provided headers in generate_kwargs
• Error handling ensures invalid JSON triggers a warning rather than failing initialization

[Copilot]

The json and os imports are being added at the top of the file, which violates the lazy loading guideline. These imports should be moved to the point of use within the __init__ method where they are actually needed. This helps minimize initial import overhead for the module.

[Copilot]

The new feature for loading headers from the DASHSCOPE_API_HEADERS environment variable lacks test coverage. Since this file has comprehensive test coverage in tests/model_dashscope_test.py, tests should be added to verify:

1. Headers are correctly loaded and parsed from the environment variable
2. Invalid JSON in the environment variable triggers a warning
3. Headers from generate_kwargs take precedence over environment headers
4. The feature works correctly when the environment variable is not set

[Copilot]

The error handling approach is unconventional. When the parsed headers are not a dictionary (line 110), the code raises a JSONDecodeError with empty arguments to trigger the exception handler. This is misleading because the JSON parsing actually succeeded - it's the type validation that failed. Consider using a TypeError or ValueError instead, or check the type before attempting JSON parsing and skip the environment variable with a warning if it's not a dictionary.

Suggested change

	if not isinstance(headers, dict):
	raise json.JSONDecodeError("", "", 0)
	if self.generate_kwargs.get("headers"):
	headers.update(self.generate_kwargs["headers"])
	self.generate_kwargs["headers"] = headers
	except json.JSONDecodeError:
	logger.warning(
	"Failed to parse DASHSCOPE_API_HEADERS environment "
	"variable as JSON. It should be a JSON object.",
	)
	except json.JSONDecodeError:
	logger.warning(
	"Failed to parse DASHSCOPE_API_HEADERS environment "
	"variable as JSON. It should be a JSON object.",
	)
	else:
	if not isinstance(headers, dict):
	logger.warning(
	"DASHSCOPE_API_HEADERS environment variable was "
	"parsed successfully but is not a JSON object. "
	"It should be a JSON object.",
	)
	else:
	if self.generate_kwargs.get("headers"):
	headers.update(self.generate_kwargs["headers"])
	self.generate_kwargs["headers"] = headers

[Copilot]

The str() conversion on line 109 is unnecessary. os.getenv() already returns a string or None, and the check on line 107 ensures that headers is truthy (not None or empty string). The str() wrapper adds no value and can be removed: headers = json.loads(headers).

Suggested change

	headers = json.loads(str(headers))
	headers = json.loads(headers)