sebmck/6to5

// @flow
import * as t from "@babel/types";
import type { TraversalAncestors, TraversalHandler } from "@babel/types";
import { parse } from "@babel/parser";
import { codeFrameColumns } from "@babel/code-frame";
import type { TemplateOpts, ParserOpts } from "./options";
import type { Formatter } from "./formatters";

export type Metadata = {
  ast: BabelNodeFile,
  placeholders: Array<Placeholder>,
  placeholderNames: Set<string>,
};

type PlaceholderType = "string" | "param" | "statement" | "other";
export type Placeholder = {|
  name: string,
  resolve: BabelNodeFile => { parent: BabelNode, key: string, index?: number },
  type: PlaceholderType,
  isDuplicate: boolean,
|};

const PATTERN = /^[_$A-Z0-9]+$/;

export default function parseAndBuildMetadata<T>(
  formatter: Formatter<T>,
  code: string,
  opts: TemplateOpts,
): Metadata {
  const {
    placeholderWhitelist,
    placeholderPattern,
    preserveComments,
    syntacticPlaceholders,
  } = opts;

  const ast = parseWithCodeFrame(code, opts.parser, syntacticPlaceholders);

  t.removePropertiesDeep(ast, {
    preserveComments,
  });

  formatter.validate(ast);

  const syntactic = {
    placeholders: [],
    placeholderNames: new Set(),
  };
  const legacy = {
    placeholders: [],
    placeholderNames: new Set(),
  };
  const isLegacyRef = { value: undefined };

  t.traverse(ast, (placeholderVisitorHandler: TraversalHandler<*>), {
    syntactic,
    legacy,
    isLegacyRef,
    placeholderWhitelist,
    placeholderPattern,
    syntacticPlaceholders,
  });

  return {
    ast,
    ...(isLegacyRef.value ? legacy : syntactic),
  };
}

function placeholderVisitorHandler(
  node: BabelNode,
  ancestors: TraversalAncestors,
  state: MetadataState,
) {
  let name;

  if (t.isPlaceholder(node)) {
    if (state.syntacticPlaceholders === false) {
      throw new Error(
        "%%foo%%-style placeholders can't be used when " +
          "'.syntacticPlaceholders' is false.",
      );
    } else {
      name = ((node: any).name: BabelNodeIdentifier).name;
      state.isLegacyRef.value = false;
    }
  } else if (state.isLegacyRef.value === false || state.syntacticPlaceholders) {
    return;
  } else if (t.isIdentifier(node) || t.isJSXIdentifier(node)) {
    name = ((node: any): BabelNodeIdentifier).name;
    state.isLegacyRef.value = true;
  } else if (t.isStringLiteral(node)) {
    name = ((node: any): BabelNodeStringLiteral).value;
    state.isLegacyRef.value = true;
  } else {
    return;
  }

  if (
    !state.isLegacyRef.value &&
    (state.placeholderPattern != null || state.placeholderWhitelist != null)
  ) {
    // This check is also in options.js. We need it there to handle the default
    // .syntacticPlaceholders behavior.
    throw new Error(
      "'.placeholderWhitelist' and '.placeholderPattern' aren't compatible" +
        " with '.syntacticPlaceholders: true'",
    );
  }

  if (
    state.isLegacyRef.value &&
    (state.placeholderPattern === false ||
      !(state.placeholderPattern || PATTERN).test(name)) &&
    !state.placeholderWhitelist?.has(name)
  ) {
    return;
  }

  // Keep our own copy of the ancestors so we can use it in .resolve().
  ancestors = ancestors.slice();

  const { node: parent, key } = ancestors[ancestors.length - 1];

  let type: PlaceholderType;
  if (
    t.isStringLiteral(node) ||
    t.isPlaceholder(node, { expectedNode: "StringLiteral" })
  ) {
    type = "string";
  } else if (
    (t.isNewExpression(parent) && key === "arguments") ||
    (t.isCallExpression(parent) && key === "arguments") ||
    (t.isFunction(parent) && key === "params")
  ) {
    type = "param";
  } else if (t.isExpressionStatement(parent) && !t.isPlaceholder(node)) {
    type = "statement";
    ancestors = ancestors.slice(0, -1);
  } else if (t.isStatement(node) && t.isPlaceholder(node)) {
    type = "statement";
  } else {
    type = "other";
  }

  const { placeholders, placeholderNames } = state.isLegacyRef.value
    ? state.legacy
    : state.syntactic;

  placeholders.push({
    name,
    type,
    resolve: ast => resolveAncestors(ast, ancestors),
    isDuplicate: placeholderNames.has(name),
  });
  placeholderNames.add(name);
}

function resolveAncestors(ast: BabelNodeFile, ancestors: TraversalAncestors) {
  let parent: BabelNode = ast;
  for (let i = 0; i < ancestors.length - 1; i++) {
    const { key, index } = ancestors[i];

    if (index === undefined) {
      parent = (parent: any)[key];
    } else {
      parent = (parent: any)[key][index];
    }
  }

  const { key, index } = ancestors[ancestors.length - 1];

  return { parent, key, index };
}

type MetadataState = {
  syntactic: {
    placeholders: Array<Placeholder>,
    placeholderNames: Set<string>,
  },
  legacy: {
    placeholders: Array<Placeholder>,
    placeholderNames: Set<string>,
  },
  isLegacyRef: { value: boolean | void },
  placeholderWhitelist: Set<string> | void,
  placeholderPattern: RegExp | false | void,
  syntacticPlaceholders: boolean | void,
};

function parseWithCodeFrame(
  code: string,
  parserOpts: ParserOpts,
  syntacticPlaceholders?: boolean,
): BabelNodeFile {
  const plugins = (parserOpts.plugins || []).slice();
  if (syntacticPlaceholders !== false) {
    plugins.push("placeholders");
  }

  parserOpts = {
    allowReturnOutsideFunction: true,
    allowSuperOutsideMethod: true,
    sourceType: "module",
    ...parserOpts,
    plugins,
  };

  try {
    // $FlowFixMe - The parser AST is not the same type as the babel-types type.
    return parse(code, parserOpts);
  } catch (err) {
    const loc = err.loc;
    if (loc) {
      err.message += "\n" + codeFrameColumns(code, { start: loc });
      err.code = "BABEL_TEMPLATE_PARSE_ERROR";
    }
    throw err;
  }
}