Don't throw in directory_entry::refresh if the file doesn't exist.

This makes directory_entry::status, directory_entry::symlink_status, as well
as related methods behave similarly to the equivalent standalone operations.

std::filesystem specification for directory_entry::refresh doesn't explicitly
say that the file not existing is not an error, but it does say that
directory_entry::status and directory_entry::symlink_status should behave
the same way as the standalone operations. Currently, libstdc++, libc++
and MSVC standard library all avoid throwing the exception from
directory_entry::refresh if the file doesn't exist.

Closes #314.

doc/release_history.html

@@ -45,6 +45,7 @@ <h2>1.86.0</h2>
   <li><code>is_empty</code> operation is now better protected against concurrent filesystem modifications.</li>
   <li>On POSIX systems, <code>is_empty</code> now indicates error if invoked on a file other than a regular file or a directory.</li>
   <li>On Windows, fixed <code>file_size</code> and <code>is_empty</code> operating on symlinks rather than the files the symlinks refer to. (<a href="https://github.com/boostorg/filesystem/issues/313">#313</a>)</li>
+  <li><code>directory_entry::refresh</code> no longer throws an exception if the file referenced by the entry doesn't exist. This makes <code>directory_entry::status</code> and <code>directory_entry::symlink_status</code>, as well as methods based on them, behave similarly to the equivalent standalone operations. The fact that the file does not exist is still indicated via the <code>error_code</code> returned by the corresponding <code>directory_entry::refresh</code> overload, or can be seen by testing if the file type returned by <code>directory_entry::status</code> or <code>directory_entry::symlink_status</code> calls is <code>file_type::file_not_found</code>. (<a href="https://github.com/boostorg/filesystem/issues/314">#314</a>)</li>
 </ul>
 
 <h2>1.85.0</h2>

src/directory.cpp

@@ -91,25 +91,15 @@ namespace filesystem {
 
 BOOST_FILESYSTEM_DECL void directory_entry::refresh_impl(system::error_code* ec) const
 {
-    system::error_code local_ec;
-    m_symlink_status = detail::symlink_status(m_path, &local_ec);
+    m_status = filesystem::file_status();
+    m_symlink_status = filesystem::file_status();
+
+    m_symlink_status = detail::symlink_status(m_path, ec);
 
     if (!filesystem::is_symlink(m_symlink_status))
     {
         // Also works if symlink_status fails - set m_status to status_error as well
         m_status = m_symlink_status;
-
-        if (BOOST_UNLIKELY(!!local_ec))
-        {
-            if (!ec)
-                BOOST_FILESYSTEM_THROW(filesystem_error("boost::filesystem::directory_entry::refresh", m_path, local_ec));
-
-            *ec = local_ec;
-            return;
-        }
-
-        if (ec)
-            ec->clear();
     }
     else
     {

test/operations_test.cpp

@@ -603,6 +603,23 @@ void directory_iterator_tests()
         BOOST_TEST_EQ(vec[3].path().filename().string(), std::string("f1"));
     }
 
+    // Test that querying a file status for a removed file referenced by the iterator
+    // doesn't cause an error (i.e. the behavior is similar to standalone status/symlink_status).
+    // https://github.com/boostorg/filesystem/issues/314
+    {
+        BOOST_TEST(fs::is_empty(d2));
+        create_file(d2 / "file");
+        fs::directory_iterator it(d2);
+        fs::remove(d2 / "file");
+
+        for (; it != fs::directory_iterator(); ++it)
+        {
+            it->symlink_status();
+            it->status();
+            it->refresh();
+        }
+    }
+
     { // *i++ must meet the standard's InputIterator requirements
         fs::directory_iterator dir_itr(dir);
         BOOST_TEST(dir_itr != fs::directory_iterator());