Hacking "check ast" into node_modules/prettier/bin/prettier.js at the bottom of `function format(argv, input, opt) {`

hacked_prettier_snippet.js

// 

// at the bottom of `function format(argv, input, opt) {`, near line 20367
  const pp = prettier$3.format(input, opt);
  const ast = cleanAST(prettier$3.__debug.parse(input, opt));
  const past = cleanAST(prettier$3.__debug.parse(pp, opt));

  if (ast !== past) {
    const MAX_AST_SIZE = 2097152; // 2MB
    const astDiff =
      ast.length > MAX_AST_SIZE || past.length > MAX_AST_SIZE
        ? "AST diff too large to render"
        : diff(ast, past);

    const safeJsxChanges = [
        '"children": []',
        '"children": [',
        '{',
        '"type": "JSXExpressionContainer",',
        '"expression": {',
        '"type": "StringLiteral",',
        '"value": " "',
        '},',
        '}',
        ']',
        '],',
    ]
    const safeNameRegex = /"name": "(\w+)",?/

    const minusLines = astDiff
      .split('\n')
      .filter(l => l.match(/^\-\s+\S/))
      .map(l => l.replace(/^\-\s+/, ''));
    const plusLines = astDiff
      .split('\n')
      .filter(l => l.match(/^\+\s+\S/))
      .map(l => l.replace(/^\+\s+/, ''));

    const unsafePlusLines = plusLines.filter(l => {
      if (safeJsxChanges.includes(l)) return false;
      if (l.match(/"type": "Identifier",?/)) return false;
      if (
        l.match(safeNameRegex) &&
        minusLines.join('').includes(`"value": "${l.match(safeNameRegex)[1]}"`)
      ) return false;
      return true;
    });
    const unsafeMinusLines = minusLines.filter(l => {
      if (safeJsxChanges.includes(l)) return false;
      if (l.match(/"type": "StringLiteral",?/)) return false;
      if (l.match(/"value": "\w+",?/)) return false;
      return true;
    });

    if (unsafePlusLines.length === 0 && unsafeMinusLines.length === 0) {
      console.log()
      console.warn('Safe diff:')
      console.warn(astDiff)
    } else {
      throw new errors.DebugError(
        "ast(input) !== ast(prettier(input))\n" +
          astDiff +
          "\n" //+
          // diff(input, pp)
      );
    }
  }