Google Cloud Functions测试出现Expecting value错误求助

First, let's clarify what this error signals: it’s thrown when json.loads() tries to parse an empty string or content that isn’t valid JSON. Since your function runs smoothly with real Pub/Sub triggers but fails only during testing, the issue is almost certainly tied to how test payloads are structured or handled in your code.

Here’s how to diagnose and fix it:

• Validate your test payload structure
  When testing a Pub/Sub-triggered Cloud Function, the test event must match the actual Pub/Sub message format. The GCF test interface might default to an empty or invalid payload if you don’t explicitly configure it. Ensure your test event includes a properly base64-encoded data field with valid JSON content. For example:

  {
    "data": "eyJ0ZXN0X2tleSI6ICJ0ZXN0X3ZhbHVlIn0=",
    "attributes": {}
  }
  

  The data value here is base64-encoded JSON ({"test_key": "test_value"}). If you leave data empty or use an invalid base64 string, decoding it will result in an empty string, triggering the JSON parse error.

• Add fault tolerance for empty/malformed payloads
  Even if real Pub/Sub messages always have valid data, test scenarios might not. Wrap your JSON parsing logic in a try-except block or add a check for empty content before parsing:

  import base64
  import json
  
  def my_function(event, context):
      data = event.get('data')
      if not data:
          print("No data provided in the message")
          return
      try:
          decoded_data = base64.b64decode(data).decode('utf-8')
          payload = json.loads(decoded_data)
      except (json.JSONDecodeError, ValueError) as e:
          print(f"Failed to parse payload: {str(e)}")
          return
      # Rest of your function logic
  

  This ensures test runs won’t crash even if the payload is malformed or empty.

• Check for changes in GCF’s default test payload
  You noted the function worked fine in July—it’s possible the default test payload for Pub/Sub triggers was updated in the GCF console. Double-check that you’re using the correct Pub/Sub test template and haven’t accidentally cleared or modified the payload fields.

• Inspect test-specific function logs
  Go to the Cloud Functions section in the GCP Console, select your function, and filter logs to view only test invocations. You’ll see the exact event structure being passed to your function, which can confirm if the data field is missing or invalid.

内容的提问来源于stack exchange，提问作者saikumar