Fix bom trimming (#543)

Author: SimonCropp

src/Directory.Build.props

@@ -2,7 +2,7 @@
 <Project>
   <PropertyGroup>
     <NoWarn>CS1591;CS0649;xUnit1026;xUnit1013;msb3277;CS0436</NoWarn>
-    <Version>17.1.3</Version>
+    <Version>17.1.4</Version>
     <ImplicitUsings>enable</ImplicitUsings>
     <LangVersion>10</LangVersion>
     <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>

src/Verify/IoHelpers.cs

@@ -2,8 +2,6 @@
 {
     static readonly UTF8Encoding Utf8 = new(true, true);
 
-    static readonly string UTF8Preamble = Encoding.UTF8.GetString(Encoding.UTF8.GetPreamble());
-
     public static void DeleteIfEmpty(string path)
     {
         var info = new FileInfo(path);
@@ -45,19 +43,9 @@ static async Task<string> ReadStringWithFixedLines(this Stream stream)
         return builder.ToString();
     }
 
-    static string TrimPreamble(string text)
-    {
-        if (text.StartsWith(UTF8Preamble))
-        {
-            return text.Substring(UTF8Preamble.Length);
-        }
-
-        return text;
-    }
-
 #if NETSTANDARD2_1 || NET5_0_OR_GREATER
     public static Task WriteText(string path, string text) =>
-        File.WriteAllTextAsync(path, TrimPreamble(text), Utf8);
+        File.WriteAllTextAsync(path, text, Utf8);
 
     public static async Task<string> ReadStringWithFixedLines(string path)
     {
@@ -80,7 +68,7 @@ public static async Task WriteStream(string path, Stream stream)
 #else
     public static async Task WriteText(string path, string text)
     {
-        var encodedText = Utf8.GetBytes(TrimPreamble(text));
+        var encodedText = Utf8.GetBytes(text);
 
         using var stream = OpenWrite(path);
         await stream.WriteAsync(encodedText, 0, encodedText.Length);

src/Verify/Verifier/InnerVerifier_Inner.cs

@@ -58,12 +58,17 @@ bool TryGetTargetBuilder(object? target, [NotNullWhen(true)] out StringBuilder?
             return true;
         }
 
-        if (!hasAppends && target is string stringTarget)
+        if (target is string stringTarget)
         {
-            builder = new(stringTarget);
-            builder.FixNewlines();
-            extension = settings.ExtensionOrTxt();
-            return true;
+            target = stringTarget = TrimPreamble(stringTarget);
+
+            if (!hasAppends)
+            {
+                builder = new(stringTarget);
+                builder.FixNewlines();
+                extension = settings.ExtensionOrTxt();
+                return true;
+            }
         }
 
         extension = "txt";
@@ -77,4 +82,7 @@ bool TryGetTargetBuilder(object? target, [NotNullWhen(true)] out StringBuilder?
 
         return true;
     }
+
+    static string TrimPreamble(string text) =>
+        text.TrimStart('\uFEFF');
 }