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Overview

To maintain consistency and security, all Stratus functions are validated before they are saved. This guide explains the required syntax, module restrictions, and best practices to help you create functions that pass validation.

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Module Export & Handler Function

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Single Handler Export

Your code must export exactly one handler function.

Exporting multiple handler definitions or not exporting a handler at all will cause validation to fail.

// ❌ Incorrect – no exported handler:
const handler = async (input, output) => { ... };

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Proper Export Format

Always export your handler as a property of module.exports.

// ✅ Correct:
module.exports.handler = async (input, output) => {
  // Function body...
};

The exported handler must be a function. Assigning non-function values (e.g., a string) will trigger an error.

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Handler Function Parameters & Behavior

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Parameter Requirements

The handler function must accept exactly two parameters:

  • input – holds input data
  • output – provides methods for setting and building the function’s output
module.exports.handler = async (input, output) => { ... };

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Using output.setResult

Inside your handler, you must call output.setResult to set the result object.

// ❌ Incorrect:
module.exports.handler = async (input, output) => {
  // Missing call to output.setResult
  return output.buildOutput();
};

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Calling output.buildOutput()

The handler must return the result of output.buildOutput(). Omitting this call is not allowed.

// ✅ Correct:
module.exports.handler = async (input, output) => {
  output.setResult({ message: "Hello" });
  return output.buildOutput();
};

If the handler does not accept exactly two parameters, validation will fail with a message similar to: “The ‘handler’ function must accept exactly two parameters: ‘input’ and ‘output’.”

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Module Import Requirements

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Allowed Modules

You may include external modules via require(), but only approved packages are allowed:

  • axios
  • lodash
  • viem and its approved subpath viem/chains
const axios = require('axios');

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Disallowed Modules

The following are not allowed:

  • Modules not on the approved list (e.g., Node’s fs)
  • Unapproved subpaths from approved packages
  • Dynamic requires (using variables for module names)
// ❌ Incorrect:
const mod = 'axios';
const axios = require(mod); // Dynamic require not allowed

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Extra Exports

Adding extra properties to module.exports (aside from the handler) is allowed and will not affect validation:

module.exports.extra = "some extra value";
module.exports.handler = async (input, output) => {
  output.setResult({ message: "Hello" });
  return output.buildOutput();
};

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JavaScript Syntax

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Valid JavaScript

Your code must be syntactically valid JavaScript. Common syntax errors include:

  • Missing closing braces
  • Unmatched parentheses
  • Invalid syntax
// ❌ Example of Syntax Error:
module.exports.handler = async (input, output) => {
  output.setResult({ message: "Hello" })
  return output.buildOutput(;  // Error: Unmatched parenthesis
};

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Common Validation Error Messages

You may encounter the following validation errors:

"Module 'unknown/chains' is not approved"
"User code must export exactly one handler function"
"Invalid dynamic require detected"
"Failed to validate user code: ..."
"The 'handler' property must be assigned to a function"
"Multiple handler definitions found"
"The 'handler' function must accept exactly two parameters: 'input' and 'output'"
"The 'handler' function must use output.setResult"
"The 'handler' function must call output.buildOutput()"

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Examples

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Valid Stratus Function with External Module

const axios = require('axios');

module.exports.handler = async (input, output) => {
  const response = await axios.get("https://example.com");
  output.setResult({ data: response.data });
  return output.buildOutput();
};

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Valid Function Without External Modules

module.exports.handler = async (input, output) => {
  output.setResult({ message: "Hello World!" });
  return output.buildOutput();
};

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Common Mistakes

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Summary

To ensure your Stratus function passes syntax validation:

  • Export one handler function using the correct module export syntax
  • Ensure the handler is asynchronous and accepts exactly two parameters: input and output
  • Call both output.setResult and output.buildOutput() within your handler
  • Import only approved modules using string literals (no dynamic requires)
  • Write valid JavaScript with correct syntax

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