Objective validator that uses the stored Python runtime

validator.js

const path = require('path');
const jetpack = require('fs-jetpack');
const { 
  NiceError, 
  executeScript, 
  checkSetup,
  executePythonCode 
} = require('../../validation');

// Append this python code to the user-created code - it will execute and
// validate that the user's script did what we expected
const VALIDATION_PYTHON_CODE = `

# Validate variables have been declared
assert 'hail_friend' in locals(), "The 'hail_friend' function was not created."

# Assert hail_friend is a function
assert callable(hail_friend), "hail_friend is not a callable function."

# Call the function so we can inspect stdout
hail_friend()
`;

module.exports = async helper => {
  try {
    const py = helper.env.TQ_PYTHON_EXE;
    const programPath = path.join(
      helper.env.TQ_PYTHON_CODE_PATH,
      'functions.py'
    );

    // Ensure prerequisite stuff is set up
    await checkSetup(py, programPath);

    // Our test args
    const ARGS = [];

    // Execute the player's script to ensure it runs
    const stdout = await executeScript(py, programPath, ARGS);
    console.log(stdout);

    // Now, do an assertion check of the code with our own python code appended
    const code = await jetpack.readAsync(programPath);
    const testCode = `${code}\n\n${VALIDATION_PYTHON_CODE}`;
    
    const testResult = await executePythonCode(helper.env, testCode, ARGS);
    console.log(testResult);
    if (testResult.exitCode !== 0) {
      if (testResult.stderr.indexOf('AssertionError:') > 0) {
        const assertionText = testResult.stderr.split('AssertionError:')[1];
        throw new NiceError(`
          Looks like there's a small problem. ${assertionText}
        `);
      } else {
        throw new NiceError(`
          We couldn't validate your Python code - please try again.
        `);
      }
    } else if (testResult.stdout.toLowerCase().indexOf('hail, friend') < 0) {
      // It should contain the text "hail, friend"
      throw new NiceError(`
        We didn't see the requested string of text output by your
        <span class="highlight">hail_friend</span> function. It needs to print
        the string "Hail, friend!"
      `);
    }

    // If we make it this far, we've passed validation
    helper.success(`
      Well done! Not only did you put the "fun" in "function", you also passed
      the <em>Trial of Reusability</em>.
    `);
  } catch (e) {
    console.log(e);
    if (e.name === 'NiceError') {
      helper.fail(e.message);
    } else {
      helper.fail(`
        Sorry! We couldn't successfully run your Python script.
      `);
    }
  }
};