Make config writer use XmlWriter for disk write

... instead of doing XmlWriter -> string -> disk.
- This guarantees that the file encoding and the XML declaration are
  properly in sync.
- Adds a `saveNormalizedXml` function to Utils to facilitate this.
- Adds a test to UtilsSpecs for the new function.
- Updates ConfigFile.saveConfigNode to use the new function.
- Should fix #2003 permanently.
- Removes the previous fix in commit d1d06b7

src/Paket.Core/ConfigFile.fs

@@ -17,13 +17,6 @@ let private rootElement = "configuration"
 let private getConfigNode (nodeName : string) =
     let rootNode = 
         let doc = XmlDocument ()
-
-        let xmldecl = doc.CreateXmlDeclaration("1.0",null,null)
-        xmldecl.Encoding <- "UTF-8"
-        xmldecl.Standalone <- "yes"
-
-        doc.InsertBefore(xmldecl, doc.DocumentElement) |> ignore
-
         if File.Exists Constants.PaketConfigFile then 
             try 
                 use f = File.OpenRead(Constants.PaketConfigFile)
@@ -49,7 +42,7 @@ let private getConfigNode (nodeName : string) =
 let private saveConfigNode (node : XmlNode) =
     trial {
         do! createDir Constants.PaketConfigFolder
-        do! saveFile Constants.PaketConfigFile (normalizeXml node.OwnerDocument)
+        do! saveNormalizedXml Constants.PaketConfigFile node.OwnerDocument
     }
 
 

src/Paket.Core/Utils.fs

@@ -316,6 +316,19 @@ let inline normalizeXml (doc:XmlDocument) =
     xmlTextWriter.Flush()
     stringWriter.GetStringBuilder() |> string
 
+let saveNormalizedXml (fileName:string) (doc:XmlDocument) =
+    // combination of saveFile and normalizeXml which ensures that the
+    // file encoding matches the one listed in the XML itself.
+    tracefn "Saving xml %s" fileName
+    let settings = XmlWriterSettings (Indent=true)
+
+    try
+        use fstream = File.Create(fileName)
+        use xmlTextWriter = XmlWriter.Create(fstream, settings)
+        doc.WriteTo(xmlTextWriter) |> ok
+    with _ ->
+        FileSaveError fileName |> fail
+
 let normalizeFeedUrl (source:string) =
     match source.TrimEnd([|'/'|]) with
     | "https://api.nuget.org/v3/index.json" -> Constants.DefaultNuGetV3Stream 

tests/Paket.Tests/UtilsSpecs.fs

@@ -6,6 +6,8 @@ open NUnit.Framework
 open FsUnit
 open System
 open System.Net
+open Chessie.ErrorHandling
+open System.Xml
 
 [<Test>]
 let ``createRelativePath should handle spaces``() =
@@ -252,4 +254,20 @@ let ``should simplify path``() =
     System.IO.Path.IsPathRooted p2 |> shouldEqual true
     System.IO.Path.IsPathRooted p3 |> shouldEqual false
     System.IO.Path.GetFullPath p1 |> shouldEqual (System.IO.Path.GetFullPath p2)
-    System.IO.Path.Combine(normalizePath p0,normalizePath p3) |> Path.GetFullPath |> shouldEqual (System.IO.Path.GetFullPath p2)
+    System.IO.Path.Combine(normalizePath p0,normalizePath p3) |> Path.GetFullPath |> shouldEqual (System.IO.Path.GetFullPath p2)
+
+[<Test>]
+let ``saving new XML file should produce valid XML``() =
+    let tempFile = Path.GetTempFileName ()
+    try
+        let doc = XmlDocument ()
+        doc.AppendChild(doc.CreateElement("configuration")) |> ignore
+        saveNormalizedXml tempFile doc |> shouldEqual (ok ())
+        let newDoc = XmlDocument ()
+        use f = File.OpenRead(tempFile)
+        newDoc.Load f
+        if not (newDoc.FirstChild :? XmlDeclaration) then
+            failwith "Generated XML should contain a declaration"
+    finally
+        if File.Exists(tempFile) then
+            File.Delete(tempFile)