Keep original line ending in merge postactions

code/src/CoreTemplateStudio/CoreTemplateStudio.Core/Helpers/FileHelper.cs

@@ -4,6 +4,9 @@
 
 using System;
 using System.IO;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
 
 namespace Microsoft.Templates.Core.Helpers
 {
@@ -25,5 +28,45 @@ public static string GetFileContent(string filePath)
                 return string.Empty;
             }
         }
+
+        public static Encoding GetEncoding(string originalFilePath)
+        {
+            // Will read the file, and look at the BOM to check the encoding.
+            using (var reader = new StreamReader(File.OpenRead(originalFilePath), true))
+            {
+                var bytes = File.ReadAllBytes(originalFilePath);
+                var encoding = reader.CurrentEncoding;
+
+                // The preamble is the first couple of bytes that may be appended to define an encoding.
+                var preamble = encoding.GetPreamble();
+
+                // We preserve the read encoding unless there is no BOM, if it is UTF-8 we return the non BOM encoding.
+                if (preamble == null || preamble.Length == 0 || preamble.Where((p, i) => p != bytes[i]).Any())
+                {
+                    if (encoding.EncodingName == Encoding.UTF8.EncodingName)
+                    {
+                        return new UTF8Encoding(false);
+                    }
+                }
+
+                return encoding;
+            }
+        }
+
+        public const string LineEndingWindows = "\r\n";
+        public const string LineEndingUnix = "\n";
+
+        public static string GetLineEnding(string originalFilePath)
+        {
+            // Will read the file, and check last file ending.
+            using (var reader = new StreamReader(File.OpenRead(originalFilePath), true))
+            {
+                var fileContent = File.ReadAllText(originalFilePath);
+                string pattern = @"(\n)|(\r\n)";
+                var lineEnding = Regex.Match(fileContent, pattern, RegexOptions.RightToLeft);
+
+                return lineEnding.Value;
+            }
+        }
     }
 }

code/src/CoreTemplateStudio/CoreTemplateStudio.Core/PostActions/Catalog/AddJsonDictionaryItem/AddJsonDictionaryItemPostAction.cs

@@ -7,7 +7,9 @@
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Text.RegularExpressions;
 using Microsoft.TemplateEngine.Abstractions;
+using Microsoft.Templates.Core.Helpers;
 using Microsoft.Templates.Core.Templates;
 using Newtonsoft.Json;
 using Newtonsoft.Json.Linq;
@@ -48,33 +50,13 @@ internal override void ExecuteInternal()
 
             json[keyToDict] = JObject.FromObject(newContent);
 
-            var originalEncoding = GetEncoding(jsonPath);
+            string lineEndingPattern = @"(\n)|(\r\n)";
+            var originalEncoding = FileHelper.GetEncoding(jsonPath);
+            var originalLineEnding = FileHelper.GetLineEnding(jsonPath);
+
+            var jsonString = Regex.Replace(json.ToString(Formatting.Indented), lineEndingPattern, originalLineEnding);
 
-            File.WriteAllText(jsonPath, json.ToString(Formatting.Indented), originalEncoding);
-        }
-
-        private Encoding GetEncoding(string originalFilePath)
-        {
-            // Will read the file, and look at the BOM to check the encoding.
-            using (var reader = new StreamReader(File.OpenRead(originalFilePath), true))
-            {
-                var bytes = File.ReadAllBytes(originalFilePath);
-                var encoding = reader.CurrentEncoding;
-
-                // The preamble is the first couple of bytes that may be appended to define an encoding.
-                var preamble = encoding.GetPreamble();
-
-                // We preserve the read encoding unless there is no BOM, if it is UTF-8 we return the non BOM encoding.
-                if (preamble == null || preamble.Length == 0 || preamble.Where((p, i) => p != bytes[i]).Any())
-                {
-                    if (encoding.EncodingName == Encoding.UTF8.EncodingName)
-                    {
-                        return new UTF8Encoding(false);
-                    }
-                }
-
-                return encoding;
-            }
+            File.WriteAllText(jsonPath, jsonString, originalEncoding);
         }
     }
 }