Handle optional function args better internally

src/EdgeDB.Net.QueryBuilder/Grammar/Terms.cs

@@ -138,8 +138,17 @@ public static QueryWriter Function(this QueryWriter writer, string name, Deferra
 
                 for (var i = 0; i < args.Length;)
                 {
+                    int commaPos = 0;
+                    LooseLinkedList<Value>.Node? comma = null;
+
+                    if (i > 0)
+                    {
+                        commaPos = writer.TailIndex;
+                        writer.Append(", ", out comma);
+                    }
+
                     var arg = args[i++];
-                    bool isEmpty = false;
+                    var isEmpty = false;
 
                     writer.Marker(
                         MarkerType.FunctionArg,
@@ -148,24 +157,25 @@ public static QueryWriter Function(this QueryWriter writer, string name, Deferra
                         Value.Of(
                             writer =>
                             {
-                                if (writer.AppendIsEmpty(arg.Value, out _, out var node))
+                                if (arg.Named is not null)
                                 {
-                                    isEmpty = true;
-                                    return;
+                                    writer.AppendPrefixIfNotEmpty(
+                                        Value.Of(writer => writer.Append(arg.Named, " := ")),
+                                        arg.Value,
+                                        out isEmpty
+                                    );
+                                }
+                                else
+                                {
+                                    writer.Append(arg.Value);
                                 }
-
-                                // append the named part if its specified
-                                if (arg.Named is not null)
-                                    writer.Prepend(node, Value.Of(writer => writer.Append(arg.Named, " := ")));
                             }
                         )
                     );
 
-                    if(isEmpty)
-                        continue;
+                    if (!isEmpty || comma is null) continue;
 
-                    if (i != args.Length)
-                        writer.Append(", ");
+                    writer.Remove(commaPos, comma);
                 }
 
                 writer.Append(')');

src/EdgeDB.Net.QueryBuilder/Lexical/QueryWriter.cs

@@ -35,7 +35,7 @@ public void Dispose()
     private ValueNode? _track;
     private readonly bool _debug;
 
-    private int TailIndex => _tokens.Count - 1;
+    public int TailIndex => _tokens.Count - 1;
 
     public QueryWriter(bool debug = false)
     {
@@ -74,8 +74,9 @@ private ValueNode AddTracked(in Value value, bool after)
             // track is already updated.
             return head ?? _track!;
         }
-        else if (_track is null)
-            _track = _tokens.AddFirst(in value); //Set(ref _tokens.AddFirst(in value));
+
+        if (_track is null)
+            _track = _tokens.AddFirst(in value);
         else
         {
             _track = after
@@ -172,6 +173,23 @@ public QueryWriter Marker(MarkerType type, string name, Deferrable<string>? debu
 
     public QueryWriter Remove(int position, ValueNode head, int count = 1)
     {
+        if (count == 0)
+            return this;
+
+        if (count < 0)
+        {
+            count *= -1;
+            var countForCopy = count - 1;
+
+            for (var i = 0; i < countForCopy; i++)
+            {
+                if (head.Previous is null)
+                    count--;
+                else
+                    head = head.Previous;
+            }
+        }
+
         var headPrev = head.Previous;
 
         _tokens.Remove(head, count, (node) =>
@@ -197,32 +215,24 @@ public QueryWriter Replace(ValueNode node, int position, int size, in Value valu
         return this;
     }
 
-    public QueryWriter Prepend(ValueNode node, in Value value)
+    public QueryWriter Append(in Value value, out ValueNode node)
     {
-        var index = GetIndexOfNode(node);
-
-        if (index == -1)
-            throw new InvalidOperationException("Node cannot be found in collection of tokens");
-
-        // change the track to the node
-        var oldTrack = _track;
+        node = AddAfterTracked(in value);
 
-        _track = node;
-        OnNodeAdd(AddBeforeTracked(in value));
-        _track = oldTrack;
+        OnNodeAdd(node);
 
-        Markers.Update(index - 1, 1);
+        Markers.Update(TailIndex, 1);
 
         return this;
     }
 
-    public QueryWriter Append(in Value value, out ValueNode node)
+    public QueryWriter Append(in Value value, out ValueNode node, out int size)
     {
-        node = AddAfterTracked(in value);
+        var pos = TailIndex;
 
-        OnNodeAdd(node);
+        Append(in value, out node);
 
-        Markers.Update(TailIndex, 1);
+        size = TailIndex - pos;
 
         return this;
     }
@@ -272,14 +282,35 @@ public bool AppendIsEmpty(in Value value)
     public bool AppendIsEmpty(in Value value, out int size)
         => AppendIsEmpty(in value, out size, out _);
 
-    public bool AppendIsEmpty(in Value value, out int size, out ValueNode node)
+    public bool AppendIsEmpty(in Value value, out int size, [MaybeNullWhen(true)] out ValueNode node)
     {
+        if (value == Value.Empty)
+        {
+            size = 0;
+            node = _track;
+            return true;
+        }
+
         var index = TailIndex;
         Append(in value, out node);
         size = TailIndex - index;
         return size == 0;
     }
 
+    public QueryWriter AppendPrefixIfNotEmpty(in Value prefix, in Value value, out bool wasEmpty)
+    {
+        var pos = TailIndex;
+        Append(in prefix, out var prefixHead, out var prefixSize);
+
+        if (AppendIsEmpty(in value))
+        {
+            Remove(pos, prefixHead, prefixSize);
+            wasEmpty = true;
+        }
+        else wasEmpty = false;
+        return this;
+    }
+
     public StringBuilder Compile(StringBuilder? builder = null)
     {
         builder ??= new StringBuilder();

src/EdgeDB.Net.QueryBuilder/Lexical/Value.cs

@@ -6,7 +6,7 @@
 namespace EdgeDB;
 
 [DebuggerDisplay("{DebugDisplay()}")]
-internal readonly struct Value
+internal readonly struct Value : IEquatable<Value>
 {
     [MemberNotNullWhen(false, nameof(_callback))]
     public bool IsScalar
@@ -104,4 +104,14 @@ public override string ToString()
     public static implicit operator Value(WriterProxy callback) => new(callback);
     public static implicit operator Value(int v) => new(v.ToString());
     public static implicit operator Value(long v) => new(v.ToString());
+
+    public bool Equals(Value other) => Equals(_callback, other._callback) && Equals(_value, other._value) && _str == other._str && _ch == other._ch;
+
+    public override bool Equals(object? obj) => obj is Value other && Equals(other);
+
+    public override int GetHashCode() => HashCode.Combine(_callback, _value, _str, _ch);
+
+    public static bool operator ==(Value left, Value right) => left.Equals(right);
+
+    public static bool operator !=(Value left, Value right) => !left.Equals(right);
 }

src/EdgeDB.Net.QueryBuilder/Translators/Methods/MethodTranslator.cs

@@ -133,7 +133,7 @@ public static void TranslateMethod(QueryWriter writer, MethodCallExpression meth
         /// </returns>
         protected Value OptionalArg(TranslatedParameter? arg)
         {
-            if (arg is null)
+            if (arg is null || arg.IsNullValue)
                 return Value.Empty;
             else
                 return arg;

src/EdgeDB.Net.QueryBuilder/Translators/Methods/TranslatedParameter.cs

@@ -51,6 +51,9 @@ public bool IsLinkType
         public bool IsMultiLinkType
             => EdgeDBTypeUtils.IsLink(ParameterType, out var isMulti, out _) && isMulti;
 
+        public bool IsNullValue
+            => RawValue is ConstantExpression {Value: null};
+
         /// <summary>
         ///     Constructs a new <see cref="TranslatedParameter"/>.
         /// </summary>