Added the get_current_file_name method to obtain the current log file

name from the text file sink backend.

Also make sure the close handler is not called when the file is not
open.

doc/changelog.qbk

@@ -11,11 +11,16 @@
 
 [heading 2.10, Boost 1.63]
 
+[*New features:]
+
+* Added a way to access the current file name from the [link log.detailed.sink_backends.text_file text file sink backend]. The file name can be obtained with the `get_current_file_name` method.
+
 [*Bug fixes:]
 
 * Fixed compilation errors for Android API prior to version 21.
 * Streaming operators now take scalar types and enums by value. This allows to output static constants and bitfields directly into formatting stream and record stream. ([ticket 11998])
 * In UDP socket based syslog backend implementation, changed the syslog message format for better compliance with RFC3164.
+* File close handler installed in [link log.detailed.sink_backends.text_file text file sink backend] is no longer called if the file is not open yet.
 
 [heading 2.9, Boost 1.62]
 

include/boost/log/sinks/text_file_backend.hpp

@@ -476,6 +476,11 @@ class text_file_backend :
      */
     BOOST_LOG_API void auto_flush(bool f = true);
 
+    /*!
+     * \return The name of the currently open log file. If no file is open, returns an empty path.
+     */
+    BOOST_LOG_API filesystem::path get_current_file_name() const;
+
     /*!
      * Performs scanning of the target directory for log files that may have been left from
      * previous runs of the application. The found files are considered by the file collector

src/text_file_backend.cpp

@@ -1176,26 +1176,28 @@ BOOST_LOG_API void text_file_backend::consume(record_view const& rec, string_typ
 {
     typedef file_char_traits< string_type::value_type > traits_t;
 
-    bool no_new_filename = false;
-    if (!m_pImpl->m_File.good())
+    filesystem::path prev_file_name;
+    bool use_prev_file_name = false;
+    if (BOOST_UNLIKELY(!m_pImpl->m_File.good()))
     {
         // The file stream is not operational. One possible reason is that there is no more free space
         // on the file system. In this case it is possible that this log record will fail to be written as well,
         // leaving the newly creted file empty. Eventually this results in lots of empty log files.
         // We should take precautions to avoid this. https://svn.boost.org/trac/boost/ticket/11016
+        prev_file_name = m_pImpl->m_FileName;
         close_file();
 
         system::error_code ec;
-        uintmax_t size = filesystem::file_size(m_pImpl->m_FileName, ec);
+        uintmax_t size = filesystem::file_size(prev_file_name, ec);
         if (!!ec || size == 0)
         {
             // To reuse the empty file avoid re-generating the new file name later
-            no_new_filename = true;
+            use_prev_file_name = true;
         }
         else if (!!m_pImpl->m_pFileCollector)
         {
             // Complete file rotation
-            m_pImpl->m_pFileCollector->store_file(m_pImpl->m_FileName);
+            m_pImpl->m_pFileCollector->store_file(prev_file_name);
         }
     }
     else if
@@ -1212,19 +1214,23 @@ BOOST_LOG_API void text_file_backend::consume(record_view const& rec, string_typ
 
     if (!m_pImpl->m_File.is_open())
     {
-        if (!no_new_filename)
-            m_pImpl->m_FileName = m_pImpl->m_StorageDir / m_pImpl->m_FileNameGenerator(m_pImpl->m_FileCounter++);
+        filesystem::path new_file_name;
+        if (!use_prev_file_name)
+            new_file_name = m_pImpl->m_StorageDir / m_pImpl->m_FileNameGenerator(m_pImpl->m_FileCounter++);
+        else
+            prev_file_name.swap(new_file_name);
 
-        filesystem::create_directories(m_pImpl->m_FileName.parent_path());
+        filesystem::create_directories(new_file_name.parent_path());
 
-        m_pImpl->m_File.open(m_pImpl->m_FileName, m_pImpl->m_FileOpenMode);
-        if (!m_pImpl->m_File.is_open())
+        m_pImpl->m_File.open(new_file_name, m_pImpl->m_FileOpenMode);
+        if (BOOST_UNLIKELY(!m_pImpl->m_File.is_open()))
         {
             BOOST_THROW_EXCEPTION(filesystem_error(
                 "Failed to open file for writing",
-                m_pImpl->m_FileName,
+                new_file_name,
                 system::error_code(system::errc::io_error, system::generic_category())));
         }
+        m_pImpl->m_FileName.swap(new_file_name);
 
         if (!m_pImpl->m_OpenHandler.empty())
             m_pImpl->m_OpenHandler(m_pImpl->m_File);
@@ -1337,29 +1343,36 @@ BOOST_LOG_API void text_file_backend::set_file_name_pattern_internal(filesystem:
 //! Closes the currently open file
 void text_file_backend::close_file()
 {
-    if (!m_pImpl->m_CloseHandler.empty())
+    if (m_pImpl->m_File.is_open())
     {
-        // Rationale: We should call the close handler even if the stream is !good() because
-        // writing the footer may not be the only thing the handler does. However, there is
-        // a chance that the file had become writable since the last failure (e.g. there was
-        // no space left to write the last record, but it got freed since then), so if the handler
-        // attempts to write a footer it may succeed now. For this reason we clear the stream state
-        // and let the handler have a try.
-        m_pImpl->m_File.clear();
-        m_pImpl->m_CloseHandler(m_pImpl->m_File);
+        if (!m_pImpl->m_CloseHandler.empty())
+        {
+            // Rationale: We should call the close handler even if the stream is !good() because
+            // writing the footer may not be the only thing the handler does. However, there is
+            // a chance that the file had become writable since the last failure (e.g. there was
+            // no space left to write the last record, but it got freed since then), so if the handler
+            // attempts to write a footer it may succeed now. For this reason we clear the stream state
+            // and let the handler have a try.
+            m_pImpl->m_File.clear();
+            m_pImpl->m_CloseHandler(m_pImpl->m_File);
+        }
+
+        m_pImpl->m_File.close();
     }
-    m_pImpl->m_File.close();
+
     m_pImpl->m_File.clear();
     m_pImpl->m_CharactersWritten = 0;
+    m_pImpl->m_FileName.clear();
 }
 
 //! The method rotates the file
 BOOST_LOG_API void text_file_backend::rotate_file()
 {
+    filesystem::path prev_file_name = m_pImpl->m_FileName;
     close_file();
 
     if (!!m_pImpl->m_pFileCollector)
-        m_pImpl->m_pFileCollector->store_file(m_pImpl->m_FileName);
+        m_pImpl->m_pFileCollector->store_file(prev_file_name);
 }
 
 //! The method sets the file open mode
@@ -1390,6 +1403,12 @@ BOOST_LOG_API void text_file_backend::set_close_handler(close_handler_type const
     m_pImpl->m_CloseHandler = handler;
 }
 
+//! The method returns name of the currently open log file. If no file is open, returns an empty path.
+BOOST_LOG_API filesystem::path text_file_backend::get_current_file_name() const
+{
+    return m_pImpl->m_FileName;
+}
+
 //! Performs scanning of the target directory for log files
 BOOST_LOG_API uintmax_t text_file_backend::scan_for_files(file::scan_method method, bool update_counter)
 {