fs: respect dereference when copy symlink directory

Co-authored-by: Jake Yuesong Li <[email protected]>

src/node_file.cc

@@ -3175,7 +3175,8 @@ static void CpSyncCheckPaths(const FunctionCallbackInfo<Value>& args) {
       return THROW_ERR_FS_CP_DIR_TO_NON_DIR(env, message.c_str());
     }
 
-    if (!src_is_dir && dest_is_dir) {
+    if (src_status.type() != std::filesystem::file_type::symlink
+        && !src_is_dir && dest_is_dir) {
       std::string message = "Cannot overwrite directory " + dest_path.string() +
                             " with non-directory " + src_path.string();
       return THROW_ERR_FS_CP_NON_DIR_TO_DIR(env, message.c_str());

test/parallel/test-fs-cp.mjs

@@ -119,6 +119,23 @@ function nextdir() {
 }
 
 
+// It overrides target directory with what symlink points to, when dereference is true.
+{
+  const src = nextdir();
+  const symlink = nextdir();
+  const dest = nextdir();
+  mkdirSync(src, mustNotMutateObjectDeep({ recursive: true }));
+  writeFileSync(join(src, 'foo.js'), 'foo', 'utf8');
+  symlinkSync(src, symlink);
+
+  mkdirSync(dest, mustNotMutateObjectDeep({ recursive: true }));
+
+  cpSync(symlink, dest, mustNotMutateObjectDeep({ dereference: true, recursive: true }));
+  const destStat = lstatSync(dest);
+  assert(!destStat.isSymbolicLink());
+  assertDirEquivalent(src, dest);
+}
+
 // It throws error when verbatimSymlinks is not a boolean.
 {
   const src = './test/fixtures/copy/kitchen-sink';