deno/ext/node/polyfills/_fs/_fs_symlink.ts

// Copyright 2018-2025 the Deno authors. MIT license.

import { primordials } from "ext:core/mod.js";

import {
  CallbackWithError,
  makeCallback,
} from "ext:deno_node/_fs/_fs_common.ts";
import { promisify } from "ext:deno_node/internal/util.mjs";
import type { Buffer } from "node:buffer";
import { validateOneOf } from "ext:deno_node/internal/validators.mjs";
import { getValidatedPathToString } from "ext:deno_node/internal/fs/utils.mjs";
import * as pathModule from "node:path";
import { isWindows } from "ext:deno_node/_util/os.ts";
import { stat, statSync } from "ext:deno_node/_fs/_fs_stat.ts";

const { PromisePrototypeThen } = primordials;

export type SymlinkType = "file" | "dir" | "junction";

export function symlink(
  target: string | Buffer | URL,
  path: string | Buffer | URL,
  linkType?: SymlinkType | CallbackWithError,
  callback?: CallbackWithError,
) {
  if (callback === undefined) {
    callback = linkType as CallbackWithError;
    linkType = undefined;
  } else {
    validateOneOf(linkType, "type", [
      "dir",
      "file",
      "junction",
      null,
      undefined,
    ]);
  }

  callback = makeCallback(callback);
  target = getValidatedPathToString(target, "target");
  path = getValidatedPathToString(path);

  if (isWindows && !linkType) {
    let absoluteTarget;
    try {
      // Symlinks targets can be relative to the newly created path.
      // Calculate absolute file name of the symlink target, and check
      // if it is a directory. Ignore resolve error to keep symlink
      // errors consistent between platforms if invalid path is
      // provided.
      absoluteTarget = pathModule.resolve(path, "..", target);
    } catch {
      // Continue regardless of error.
    }
    if (absoluteTarget !== undefined) {
      stat(absoluteTarget, (err, stat) => {
        const resolvedType = !err && stat.isDirectory() ? "dir" : "file";

        PromisePrototypeThen(
          Deno.symlink(
            target,
            path,
            { type: resolvedType },
          ),
          () => callback(null),
          callback,
        );
      });
      return;
    }
  }

  PromisePrototypeThen(
    Deno.symlink(
      target,
      path,
      { type: linkType ?? "file" },
    ),
    () => callback(null),
    callback,
  );
}

export const symlinkPromise = promisify(symlink) as (
  target: string | Buffer | URL,
  path: string | Buffer | URL,
  type?: SymlinkType,
) => Promise<void>;

export function symlinkSync(
  target: string | Buffer | URL,
  path: string | Buffer | URL,
  type?: SymlinkType,
) {
  validateOneOf(type, "type", ["dir", "file", "junction", null, undefined]);
  target = getValidatedPathToString(target, "target");
  path = getValidatedPathToString(path);

  if (isWindows && !type) {
    const absoluteTarget = pathModule.resolve(path, "..", target);
    if (
      statSync(absoluteTarget, { bigint: false, throwIfNoEntry: false })
        ?.isDirectory()
    ) {
      type = "dir";
    }
  }

  Deno.symlinkSync(target, path, { type: type ?? "file" });
}