Error handling in Modus makes it simple to have both a clear debugging process for developers and informative responses for end-users.

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Logging errors

The Console API in the Modus SDK is globally available in all functions. It allows developers to capture log messages and errors, which are automatically included in Modus runtime execution logs.
When deployed to Hypermode, function logs are available in the Hypermode Console on the Function Runs page.
The Console API provides five logging functions: 
console.log("This is a simple log message.")
console.debug("This is a debug message.")
console.info("This is an info message.")
console.warn("This is a warning message.")
console.error("This is an error message.")

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Error reporting in GraphQL

GraphQL responses have a standard structure that includes both data and errors sections. Modus allows for the inclusion of error codes or messages within the errors section to allow for downstream processing in addition to debugging. 
// in Go, error handling is typically done by returning an `error` object as the
// last result of a function; Modus transforms this into logging and error handling
// automatically, ensuring all errors are logged before being sent to the response
func TestError(input string) (string, error) {
    if input == "" {
        return "", errors.New("input is empty")
    }
    return "You said: " + input, nil
}

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Best practices for error handling

  • Handle non-fatal errors using console.error, allowing the function to continue. The GraphQL response may have both a data section and an errors section.
  • Handle critical errors using AssemblyScript throw keyword or the Go idiomatic error object to stop the function’s execution.
  • Return clear error messages: When returning errors, include concise and informative error messages that help diagnose the issue.