Make File.create() fail when a directory exists at the same path

runtime/bin/file_linux.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_LINUX)
 
 #include "bin/file.h"
 
 #include <errno.h>         // NOLINT
 #include <fcntl.h>         // NOLINT
 #include <libgen.h>        // NOLINT
 #include <sys/mman.h>      // NOLINT
 #include <sys/sendfile.h>  // NOLINT
 #include <sys/stat.h>      // NOLINT
 #include <sys/types.h>     // NOLINT
 #include <unistd.h>        // NOLINT
 
 #include "bin/builtin.h"
+#include "bin/fdutils.h"
 #include "bin/log.h"
 #include "platform/signal_blocker.h"
 #include "platform/utils.h"
 
 namespace dart {
 namespace bin {
 
 class FileHandle {
  public:
   explicit FileHandle(int fd) : fd_(fd) {}
@@ skipping 190 matching lines @@
 
 
 File* File::OpenStdio(int fd) {
   return ((fd < 0) || (2 < fd)) ? NULL : new File(new FileHandle(fd));
 }
 
 
 bool File::Exists(const char* name) {
   struct stat64 st;
   if (TEMP_FAILURE_RETRY(stat64(name, &st)) == 0) {
-    return S_ISREG(st.st_mode);
+    // Everything but a directory and a link is a file to Dart.
+    return !S_ISDIR(st.st_mode) && !S_ISLNK(st.st_mode);
   } else {
     return false;
   }
 }
 
 
 bool File::Create(const char* name) {
   int fd =
       TEMP_FAILURE_RETRY(open64(name, O_RDONLY | O_CREAT | O_CLOEXEC, 0666));
   if (fd < 0) {
     return false;
   }
-  return (TEMP_FAILURE_RETRY(close(fd)) == 0);
+  // File.create returns a File, so we shouldn't be giving the illusion that the
+  // call has created a file or that a file already exists if there is already
+  // an entity at the same path that is a directory or a link.
+  bool is_file = true;
+  struct stat64 st;
+  if (TEMP_FAILURE_RETRY(fstat64(fd, &st)) == 0) {
+    if (S_ISDIR(st.st_mode)) {
+      errno = EISDIR;
+      is_file = false;
+    } else if (S_ISLNK(st.st_mode)) {
+      errno = ENOENT;
+      is_file = false;
+    }
+  }
+  FDUtils::SaveErrorAndClose(fd);
+  return is_file;
 }
 
 
 bool File::CreateLink(const char* name, const char* target) {
   return NO_RETRY_EXPECTED(symlink(target, name)) == 0;
 }
 
 
 bool File::Delete(const char* name) {
   File::Type type = File::GetType(name, true);
@@ skipping 265 matching lines @@
   return ((file_1_info.st_ino == file_2_info.st_ino) &&
           (file_1_info.st_dev == file_2_info.st_dev))
              ? File::kIdentical
              : File::kDifferent;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_LINUX)