FileTarget fix: CreatedDir setting when replacing file content

src/NLog/Targets/FileTarget.cs

@@ -1822,7 +1822,7 @@ private void WriteToFile(string fileName, LogEventInfo logEvent, byte[] bytes, b
         {
             if (this.ReplaceFileContentsOnEachWrite)
             {
-                ReplaceFileContent(fileName, bytes);
+                ReplaceFileContent(fileName, bytes, true);
                 return;
             }
 
@@ -1957,24 +1957,38 @@ private void ProcessOnStartup(string fileName, LogEventInfo logEvent)
         /// </summary>
         /// <param name="fileName">The name of the file to be written.</param>
         /// <param name="bytes">Sequence of <see langword="byte"/> to be written in the content section of the file.</param>
+        /// <param name="firstAttempt">First attempt to write?</param>
         /// <remarks>This method is used when the content of the log file is re-written on every write.</remarks>
-        private void ReplaceFileContent(string fileName, byte[] bytes)
+        private void ReplaceFileContent(string fileName, byte[] bytes, bool firstAttempt)
         {
-            using (FileStream fs = File.Create(fileName))
+            try
             {
-                byte[] headerBytes = this.GetHeaderBytes();
-                if (headerBytes != null)
+                using (FileStream fs = File.Create(fileName))
                 {
-                    fs.Write(headerBytes, 0, headerBytes.Length);
-                }
+                    byte[] headerBytes = this.GetHeaderBytes();
+                    if (headerBytes != null)
+                    {
+                        fs.Write(headerBytes, 0, headerBytes.Length);
+                    }
 
-                fs.Write(bytes, 0, bytes.Length);
+                    fs.Write(bytes, 0, bytes.Length);
 
-                byte[] footerBytes = this.GetFooterBytes();
-                if (footerBytes != null)
+                    byte[] footerBytes = this.GetFooterBytes();
+                    if (footerBytes != null)
+                    {
+                        fs.Write(footerBytes, 0, footerBytes.Length);
+                    }
+                }
+            }
+            catch (DirectoryNotFoundException)
+            {
+                if (!this.CreateDirs || !firstAttempt)
                 {
-                    fs.Write(footerBytes, 0, footerBytes.Length);
+                    throw;
                 }
+                Directory.CreateDirectory(Path.GetDirectoryName(fileName));
+                //retry.
+                ReplaceFileContent(fileName, bytes, false);
             }
         }
 

tests/NLog.UnitTests/Targets/FileTargetTests.cs

@@ -414,6 +414,48 @@ public void ReplaceFileContentsOnEachWriteTest(bool useHeader, bool useFooter)
             }
         }
 
+
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public void ReplaceFileContentsOnEachWrite_CreateDirs(bool createDirs)
+        {
+
+            LogManager.ThrowExceptions = false;
+
+            var tempPath = Path.Combine(Path.GetTempPath(), "dir_" + Guid.NewGuid().ToString());
+            var logfile = Path.Combine(tempPath, "log.log");
+
+            try
+            {
+                var target = new FileTarget
+                {
+                    FileName = logfile,
+                    ReplaceFileContentsOnEachWrite = true,
+                    CreateDirs = createDirs
+                };
+                var config = new LoggingConfiguration();
+
+                config.AddTarget("logfile", target);
+
+                config.AddRuleForAllLevels(target);
+
+                LogManager.Configuration = config;
+
+                ILogger logger = LogManager.GetLogger("A");
+                logger.Info("a");
+
+                Assert.Equal(createDirs, Directory.Exists(tempPath));
+            }
+            finally
+            {
+                if (File.Exists(logfile))
+                    File.Delete(logfile);
+                if (Directory.Exists(tempPath))
+                    Directory.Delete(tempPath, true);
+            }
+        }
+
         [Fact]
         public void CreateDirsTest()
         {
@@ -2662,6 +2704,7 @@ public void BatchErrorHandlingTest()
             Assert.NotNull(exceptions[2]);
             Assert.NotNull(exceptions[3]);
         }
+
     }