Fix trivia handling

Parser.Tests/ThereAndBackAgain.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using System.Text;
 using Xunit;
 
 namespace Parser.Tests
@@ -57,6 +58,34 @@ namespace Parser.Tests
             Assert.Equal(text.Length, actualWidth);
         }
 
+        [Theory]
+        [MemberData(nameof(FilesData))]
+        public void TestLeadingAndTrailingTrivia(string fileName)
+        {
+            var text = File.ReadAllText(fileName);
+            var window = new TextWindowWithNull(text, fileName);
+            var parser = CreateParser(window);
+            var tree = parser.Parse();
+
+            var sb = new StringBuilder();
+            var maybeLeadingTrivia = tree.Root.LeadingTrivia;
+            var maybeTrailingTrivia = tree.Root.TrailingTrivia;
+            if (maybeLeadingTrivia is SyntaxTriviaList leadingTrivia)
+            {
+                sb.Append(leadingTrivia.FullText);
+            }
+
+            sb.Append(tree.Root.Text);
+
+            if (maybeTrailingTrivia is SyntaxTriviaList trailingTrivia)
+            {
+                sb.Append(trailingTrivia.FullText);
+            }
+
+            var actualText = sb.ToString();
+            Assert.Equal(text, actualText);
+        }
+
         public static IEnumerable<object[]> FilesData()
         {
             return Files().Select(fileName => new object[] { fileName });

Parser/Internal/GreenNode.cs

@@ -209,7 +209,6 @@ namespace Parser.Internal
                 }
 
                 return sb.ToString();
-
             }
         } 
 

Parser/Internal/MParserGreen.cs

@@ -1175,9 +1175,14 @@ namespace Parser.Internal
             return ParseExpressionStatement();
         }
 
-        private BlockStatementSyntaxNode ParseBlockStatement()
+        private BlockStatementSyntaxNode? ParseBlockStatement()
         {
             var statements = ParseStatementList();
+            if (statements.Length == 0)
+            {
+                return null;
+            }
+
             return Factory.BlockStatementSyntax(statements);
         }
         

Parser/Internal/SyntaxFactory.Generated.cs

@@ -3,7 +3,7 @@ namespace Parser.Internal
 {
     internal partial class SyntaxFactory
     {
-        public FileSyntaxNode FileSyntax(BlockStatementSyntaxNode body, SyntaxToken endOfFile)
+        public FileSyntaxNode FileSyntax(BlockStatementSyntaxNode? body, SyntaxToken endOfFile)
         {
             return new FileSyntaxNode(body, endOfFile);
         }

Parser/Internal/SyntaxNode.Generated.cs

@@ -3,9 +3,9 @@ namespace Parser.Internal
 {
     internal class FileSyntaxNode : SyntaxNode
     {
-        internal readonly BlockStatementSyntaxNode _body;
+        internal readonly BlockStatementSyntaxNode? _body;
         internal readonly SyntaxToken _endOfFile;
-        internal FileSyntaxNode(BlockStatementSyntaxNode body, SyntaxToken endOfFile): base(TokenKind.File)
+        internal FileSyntaxNode(BlockStatementSyntaxNode? body, SyntaxToken endOfFile): base(TokenKind.File)
         {
             Slots = 2;
             this.AdjustWidth(body);
@@ -14,7 +14,7 @@ namespace Parser.Internal
             _endOfFile = endOfFile;
         }
 
-        internal FileSyntaxNode(BlockStatementSyntaxNode body, SyntaxToken endOfFile, TokenDiagnostic[] diagnostics): base(TokenKind.File, diagnostics)
+        internal FileSyntaxNode(BlockStatementSyntaxNode? body, SyntaxToken endOfFile, TokenDiagnostic[] diagnostics): base(TokenKind.File, diagnostics)
         {
             Slots = 2;
             this.AdjustWidth(body);

Parser/Internal/SyntaxNode.cs

@@ -51,7 +51,7 @@ namespace Parser.Internal
             return builder.ToString();
         }
 
-        public override string FullText => CollectFullText();
+        //public override string FullText => CollectFullText();
 
         public override GreenNode? LeadingTriviaCore => throw new NotImplementedException();
         public override GreenNode? TrailingTriviaCore => throw new NotImplementedException();

Parser/Internal/SyntaxTrivia.cs

@@ -20,6 +20,7 @@ namespace Parser.Internal
         }
 
         public override string Text => _text;
+        public override string FullText => _text;
         public int Width => _text.Length;
 
         public override GreenNode? GetSlot(int i)

Parser/SyntaxDefinition.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Syntax xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
     <Class Name="FileSyntaxNode" BaseClass="SyntaxNode" Kind="File">
-        <Field Type="BlockStatementSyntaxNode" Name="body" />
+        <Field Type="BlockStatementSyntaxNode" Name="body" Nullable="true"/>
         <Field Type="SyntaxToken" Name="endOfFile" />
     </Class>
     <Class Name="BlockStatementSyntaxNode" BaseClass="StatementSyntaxNode" Kind="BlockStatement">

Parser/SyntaxNode.Generated.cs

@@ -16,12 +16,12 @@ namespace Parser
             }
         }
 
-        public BlockStatementSyntaxNode Body
+        public BlockStatementSyntaxNode? Body
         {
             get
             {
-                var red = this.GetRed(ref this._body!, 0);
+                var red = this.GetRed(ref this._body, 0);
-                return red is null ? throw new System.Exception("body cannot be null.") : (BlockStatementSyntaxNode)red;
+                return red is null ? default : (BlockStatementSyntaxNode)red;
             }
         }
 
@@ -29,7 +29,7 @@ namespace Parser
         {
             return i switch
             {
-            0 => GetRed(ref _body!, 0), _ => null
+            0 => GetRed(ref _body, 0), _ => null
             }
 
             ;

Parser/SyntaxTriviaList.cs

@@ -36,6 +36,8 @@ namespace Parser
             }
         }
 
+        public string FullText => Node?.FullText ?? string.Empty;
+
         public IEnumerator<SyntaxTrivia> GetEnumerator()
         {
             for (var i = 0; i < Count; i++)