pug/walk.js at master · ArtCodeStudio/pug · GitHub

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export default function walkAST(ast, before, after, options) {
  if (after && typeof after === "object" && typeof options === "undefined") {
    options = after;
    after = null;
  }
  options = options || { includeDependencies: false };
  var parents = (options.parents = options.parents || []);

  var replace = function replace(replacement) {
    if (Array.isArray(replacement) && !replace.arrayAllowed) {
      throw new Error(
        "replace() can only be called with an array if the last parent is a Block or NamedBlock",
      );
    }
    ast = replacement;
  };
  replace.arrayAllowed = parents[0] &&
    (/^(Named)?Block$/.test(parents[0].type) ||
      (parents[0].type === "RawInclude" && ast.type === "IncludeFilter"));

  if (before) {
    var result = before(ast, replace);
    if (result === false) {
      return ast;
    } else if (Array.isArray(ast)) {
      // return right here to skip after() call on array
      return walkAndMergeNodes(ast);
    }
  }

  parents.unshift(ast);

  switch (ast.type) {
    case "NamedBlock":
    case "Block":
      ast.nodes = walkAndMergeNodes(ast.nodes);
      break;
    case "Case":
    case "Filter":
    case "Mixin":
    case "Tag":
    case "InterpolatedTag":
    case "When":
    case "Code":
    case "While":
      if (ast.block) {
        ast.block = walkAST(ast.block, before, after, options);
      }
      break;
    case "Each":
      if (ast.block) {
        ast.block = walkAST(ast.block, before, after, options);
      }
      if (ast.alternate) {
        ast.alternate = walkAST(ast.alternate, before, after, options);
      }
      break;
    case "EachOf":
      if (ast.block) {
        ast.block = walkAST(ast.block, before, after, options);
      }
      break;
    case "Conditional":
      if (ast.consequent) {
        ast.consequent = walkAST(ast.consequent, before, after, options);
      }
      if (ast.alternate) {
        ast.alternate = walkAST(ast.alternate, before, after, options);
      }
      break;
    case "Include":
      walkAST(ast.block, before, after, options);
      walkAST(ast.file, before, after, options);
      break;
    case "Extends":
      walkAST(ast.file, before, after, options);
      break;
    case "RawInclude":
      ast.filters = walkAndMergeNodes(ast.filters);
      walkAST(ast.file, before, after, options);
      break;
    case "Attrs":
    case "BlockComment":
    case "Comment":
    case "Doctype":
    case "IncludeFilter":
    case "MixinBlock":
    case "YieldBlock":
    case "Text":
      break;
    case "FileReference":
      if (options.includeDependencies && ast.ast) {
        walkAST(ast.ast, before, after, options);
      }
      break;
    default:
      throw new Error("Unexpected node type " + ast.type);
      break;
  }

  parents.shift();

  after && after(ast, replace);
  return ast;

  function walkAndMergeNodes(nodes) {
    return nodes.reduce(function (nodes, node) {
      var result = walkAST(node, before, after, options);
      if (Array.isArray(result)) {
        return nodes.concat(result);
      } else {
        return nodes.concat([result]);
      }
    }, []);
  }
}