bun.sh/src/codegen/replacements.ts

import { LoaderKeys } from "../api/schema";
import { sliceSourceCode } from "./builtin-parser";

// This is a list of extra syntax replacements to do. Kind of like macros
// These are only run on code itself, not string contents or comments.
export const replacements: ReplacementRule[] = [
  { from: /\bthrow new TypeError\b/g, to: "$throwTypeError" },
  { from: /\bthrow new RangeError\b/g, to: "$throwRangeError" },
  { from: /\bthrow new OutOfMemoryError\b/g, to: "$throwOutOfMemoryError" },
  { from: /\bnew TypeError\b/g, to: "$makeTypeError" },
  { from: /\bexport\s*default/g, to: "$exports =" },
];

// These rules are run on the entire file, including within strings.
export const globalReplacements: ReplacementRule[] = [
  {
    from: /\bnotImplementedIssue\(\s*([0-9]+)\s*,\s*((?:"[^"]*"|'[^']+'))\s*\)/g,
    to: "new TypeError(`${$2} is not implemented yet. See https://github.com/oven-sh/bun/issues/$1`)",
  },
  {
    from: /\bnotImplementedIssueFn\(\s*([0-9]+)\s*,\s*((?:"[^"]*"|'[^']+'))\s*\)/g,
    to: "() => $throwTypeError(`${$2} is not implemented yet. See https://github.com/oven-sh/bun/issues/$1`)",
  },
];

// This is a list of globals we should access using @ notation
// This prevents a global override attacks.
// Note that the public `Bun` global is immutable.
// undefined -> __intrinsic__undefined -> @undefined
export const globalsToPrefix = [
  "AbortSignal",
  "Array",
  "ArrayBuffer",
  "Buffer",
  "Infinity",
  "Loader",
  "Promise",
  "ReadableByteStreamController",
  "ReadableStream",
  "ReadableStreamBYOBReader",
  "ReadableStreamBYOBRequest",
  "ReadableStreamDefaultController",
  "ReadableStreamDefaultReader",
  "TransformStream",
  "TransformStreamDefaultController",
  "Uint8Array",
  "String",
  "Buffer",
  "RegExp",
  "WritableStream",
  "WritableStreamDefaultController",
  "WritableStreamDefaultWriter",
  "isFinite",
  "undefined",
];

// These enums map to $<enum>IdToLabel and $<enum>LabelToId
// Make sure to define in ./builtins.d.ts
export const enums = {
  Loader: LoaderKeys,
  ImportKind: [
    "entry-point",
    "import-statement",
    "require-call",
    "dynamic-import",
    "require-resolve",
    "import-rule",
    "url-token",
    "internal",
  ],
};

// These identifiers have typedef but not present at runtime (converted with replacements)
// If they are present in the bundle after runtime, we warn at the user.
// TODO: implement this check.
export const warnOnIdentifiersNotPresentAtRuntime = [
  //
  "OutOfMemoryError",
  "notImplementedIssue",
  "notImplementedIssueFn",
];

// These are passed to --define to the bundler
const debug = process.argv[2] === "--debug=ON";
export const define: Record<string, string> = {
  "process.env.NODE_ENV": JSON.stringify(debug ? "development" : "production"),
  "IS_BUN_DEVELOPMENT": String(debug),

  $streamClosed: "1",
  $streamClosing: "2",
  $streamErrored: "3",
  $streamReadable: "4",
  $streamWaiting: "5",
  $streamWritable: "6",

  "process.platform": JSON.stringify(Bun.env.TARGET_PLATFORM ?? process.platform),
  "process.arch": JSON.stringify(Bun.env.TARGET_ARCH ?? process.arch),
};

// ------------------------------ //

for (const name in enums) {
  const value = enums[name];
  if (typeof value !== "object") throw new Error("Invalid enum object " + name + " defined in " + import.meta.file);
  if (typeof value === null) throw new Error("Invalid enum object " + name + " defined in " + import.meta.file);
  const keys = Array.isArray(value) ? value : Object.keys(value).filter(k => !k.match(/^[0-9]+$/));
  define[`$${name}IdToLabel`] = "[" + keys.map(k => `"${k}"`).join(", ") + "]";
  define[`$${name}LabelToId`] = "{" + keys.map(k => `"${k}": ${keys.indexOf(k)}`).join(", ") + "}";
}

for (const name of globalsToPrefix) {
  define[name] = "__intrinsic__" + name;
}

for (const key in define) {
  if (key.startsWith("$")) {
    define["__intrinsic__" + key.slice(1)] = define[key];
    delete define[key];
  }
}

export interface ReplacementRule {
  from: RegExp;
  to: string;
  global?: boolean;
}

/** Applies source code replacements as defined in `replacements` */
export function applyReplacements(src: string, length: number) {
  let slice = src.slice(0, length);
  let rest = src.slice(length);
  slice = slice.replace(/([^a-zA-Z0-9_\$])\$([a-zA-Z0-9_]+\b)/gm, `$1__intrinsic__$2`);
  for (const replacement of replacements) {
    slice = slice.replace(replacement.from, replacement.to.replaceAll("$", "__intrinsic__"));
  }
  let match;
  if ((match = slice.match(/__intrinsic__(debug|assert)$/)) && rest.startsWith("(")) {
    const name = match[1];
    if (name === "debug") {
      const innerSlice = sliceSourceCode(rest, true);
      return [
        slice.slice(0, match.index) + "(IS_BUN_DEVELOPMENT?$debug_log" + innerSlice.result + ":void 0)",
        innerSlice.rest,
        true,
      ];
    } else if (name === "assert") {
      const checkSlice = sliceSourceCode(rest, true, undefined, true);
      let rest2 = checkSlice.rest;
      let extraArgs = "";
      if (checkSlice.result.at(-1) === ",") {
        const sliced = sliceSourceCode("(" + rest2.slice(1), true, undefined, false);
        extraArgs = ", " + sliced.result.slice(1, -1);
        rest2 = sliced.rest;
      }
      return [
        slice.slice(0, match.index) +
          "(IS_BUN_DEVELOPMENT?$assert(" +
          checkSlice.result.slice(1, -1) +
          "," +
          JSON.stringify(
            checkSlice.result
              .slice(1, -1)
              .replace(/__intrinsic__/g, "$")
              .trim(),
          ) +
          extraArgs +
          "):void 0)",
        rest2,
        true,
      ];
    }
  }
  return [slice, rest, false];
}

/** Applies source code replacements as defined in `globalReplacements` */
export function applyGlobalReplacements(src: string) {
  let result = src;
  for (const replacement of globalReplacements) {
    result = result.replace(replacement.from, replacement.to.replaceAll("$", "__intrinsic__"));
  }
  return result;
}