fs: fix cp handle existing symlinks

Author: jakecastelli

lib/internal/fs/cp/cp.js

@@ -54,6 +54,7 @@ const {
   resolve,
   sep,
 } = require('path');
+const fsBinding = internalBinding('fs');
 
 async function cpFn(src, dest, opts) {
   // Warn about using preserveTimestamps on 32-bit node
@@ -344,7 +345,10 @@ async function onLink(destStat, src, dest, opts) {
   if (!isAbsolute(resolvedDest)) {
     resolvedDest = resolve(dirname(dest), resolvedDest);
   }
-  if (isSrcSubdir(resolvedSrc, resolvedDest)) {
+
+  const srcIsDir = fsBinding.internalModuleStat(src) === 1;
+
+  if (srcIsDir && isSrcSubdir(resolvedSrc, resolvedDest)) {
     throw new ERR_FS_CP_EINVAL({
       message: `cannot copy ${resolvedSrc} to a subdirectory of self ` +
             `${resolvedDest}`,

test/parallel/test-fs-cp.mjs

@@ -259,7 +259,23 @@ function nextdir(dirname) {
   cpSync(src, dest, mustNotMutateObjectDeep({ recursive: true }));
 }
 
-// It throws error if symlink in dest points to location in src.
+{
+  const src = nextdir();
+  const dest = nextdir();
+  mkdirSync(src, mustNotMutateObjectDeep({ recursive: true }));
+  writeFileSync(`${src}/test.txt`, 'test');
+  symlinkSync(resolve(`${src}/test.txt`), join(src, 'link.txt'));
+  cp(src, dest, { recursive: true },
+     mustCall((err) => {
+       assert.strictEqual(err, null);
+
+       cp(src, dest, { recursive: true }, mustCall((err) => {
+         assert.strictEqual(err, null);
+       }));
+     }));
+}
+
+// It allows copying symlinks in src to locations in dest with existing synlinks not pointing to a directory.
 {
   const src = nextdir();
   mkdirSync(join(src, 'a', 'b'), mustNotMutateObjectDeep({ recursive: true }));