Avoid state machines (#303)

Fluid.Benchmarks/TagBenchmarks.cs

@@ -0,0 +1,134 @@
+using System.Runtime.CompilerServices;
+using BenchmarkDotNet.Attributes;
+
+namespace Fluid.Benchmarks
+{
+    [MemoryDiagnoser]
+    public class TagBenchmarks
+    {
+        private static readonly FluidParser _parser = new();
+        private readonly TemplateContext _context;
+        private readonly TestCase _rawTag;
+        private readonly TestCase _ifWithAnds;
+        private readonly TestCase _ifWithOrs;
+        private readonly TestCase _elseIf;
+        private readonly TestCase _assign;
+        private readonly TestCase _else;
+        private readonly TestCase _textSpan;
+
+        public TagBenchmarks()
+        {
+            _rawTag = new TestCase("before {% raw %} {{ TEST 3 }} {% endraw %} after");
+            _ifWithAnds = new TestCase("{% if true and false and false == false %}HIDDEN{% endif %}");
+            _ifWithOrs = new TestCase("{% if true == false or false or false %}HIDDEN{% endif %}");
+            _elseIf = new TestCase("{% if false %}{% elsif true == false or false or false %}HIDDEN{% endif %}");
+            _else = new TestCase("{% if false %}{% else %}SHOWN{% endif %}");
+            _assign = new TestCase("{% assign something = 'foo' %} {% assign another = 1234 %} {% assign last = something %}");
+            _textSpan = new TestCase("foo");
+
+            _context = new TemplateContext();
+        }
+
+        [Benchmark]
+        public object RawTag_Parse()
+        {
+            return _rawTag.Parse();
+        }
+
+        [Benchmark]
+        public string RawTag_Render()
+        {
+            return _rawTag.Render(_context);
+        }
+
+        [Benchmark]
+        public object IfStatement_Ands_Parse()
+        {
+            return _ifWithAnds.Parse();
+        }
+
+        [Benchmark]
+        public string IfStatement_Ands_Render()
+        {
+            return _ifWithAnds.Render(_context);
+        }
+
+        [Benchmark]
+        public object IfStatement_Ors_Parse()
+        {
+            return _ifWithOrs.Parse();
+        }
+
+        [Benchmark]
+        public string IfStatement_Ors_Render()
+        {
+            return _ifWithOrs.Render(_context);
+        }
+
+        [Benchmark]
+        public object ElseIfStatement_Parse()
+        {
+            return _elseIf.Parse();
+        }
+
+        [Benchmark]
+        public string ElseIfStatement_Render()
+        {
+            return _elseIf.Render(_context);
+        }
+
+        [Benchmark]
+        public object Assign_Parse()
+        {
+            return _assign.Parse();
+        }
+
+        [Benchmark]
+        public string Assign_Render()
+        {
+            return _assign.Render(_context);
+        }
+
+        [Benchmark]
+        public object Else_Parse()
+        {
+            return _else.Parse();
+        }
+
+        [Benchmark]
+        public string Else_Render()
+        {
+            return _else.Render(_context);
+        }
+
+        [Benchmark]
+        public object TextSpan_Parse()
+        {
+            return _textSpan.Parse();
+        }
+
+        [Benchmark]
+        public string TextSpan_Render()
+        {
+            return _textSpan.Render(_context);
+        }
+
+        private sealed class TestCase
+        {
+            private readonly string _source;
+            private readonly IFluidTemplate _template;
+
+            public TestCase(string source)
+            {
+                _source = source;
+                _template = _parser.Parse(source);
+            }
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public string Render(TemplateContext context) => _template.Render(context);
+
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            public IFluidTemplate Parse() => _parser.Parse(_source);
+        }
+    }
+}

Fluid/Ast/AssignStatement.cs

@@ -1,6 +1,7 @@
 using System.IO;
 using System.Text.Encodings.Web;
 using System.Threading.Tasks;
+using Fluid.Values;
 
 namespace Fluid.Ast
 {
@@ -16,14 +17,25 @@ public AssignStatement(string identifier, Expression value)
 
         public Expression Value { get; }
 
-        public override async ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
+        public override ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
         {
+            static async ValueTask<Completion> Awaited(ValueTask<FluidValue> task, TemplateContext context, string identifier)
+            {
+                var value = await task;
+                context.SetValue(identifier, value);
+                return Completion.Normal;
+            }
+
             context.IncrementSteps();
 
-            var value = await Value.EvaluateAsync(context);
-            context.SetValue(Identifier, value);
+            var task = Value.EvaluateAsync(context);
+            if (!task.IsCompletedSuccessfully)
+            {
+                return Awaited(task, context, Identifier);
+            }
 
-            return Completion.Normal;
+            context.SetValue(Identifier, task.Result);
+            return new ValueTask<Completion>(Completion.Normal);
         }
     }
 }

Fluid/Ast/BinaryExpression.cs

@@ -2,7 +2,7 @@
 {
     public abstract class BinaryExpression : Expression
     {
-        public BinaryExpression(Expression left, Expression right)
+        protected BinaryExpression(Expression left, Expression right)
         {
             Left = left;
             Right = right;

Fluid/Ast/BinaryExpressions/AndBinaryExpression.cs

@@ -9,12 +9,25 @@ public AndBinaryExpression(Expression left, Expression right) : base(left, right
         {
         }
 
-        public override async ValueTask<FluidValue> EvaluateAsync(TemplateContext context)
+        public override ValueTask<FluidValue> EvaluateAsync(TemplateContext context)
         {
-            var leftValue = await Left.EvaluateAsync(context);
-            var rightValue = await Right.EvaluateAsync(context);
+            static async ValueTask<FluidValue> Awaited(ValueTask<FluidValue> leftTask, ValueTask<FluidValue> rightTask)
+            {
+                var leftValue = await leftTask;
+                var rightValue = await rightTask;
 
-            return BooleanValue.Create(leftValue.ToBooleanValue() && rightValue.ToBooleanValue());
+                return BooleanValue.Create(leftValue.ToBooleanValue() && rightValue.ToBooleanValue());
+            }
+
+            var leftTask = Left.EvaluateAsync(context);
+            var rightTask = Right.EvaluateAsync(context);
+
+            if (leftTask.IsCompletedSuccessfully && rightTask.IsCompletedSuccessfully)
+            {
+                return BooleanValue.Create(leftTask.Result.ToBooleanValue() && rightTask.Result.ToBooleanValue());
+            }
+
+            return Awaited(leftTask, rightTask);
         }
     }
 }

Fluid/Ast/BinaryExpressions/OrBinaryExpression.cs

@@ -9,12 +9,25 @@ public OrBinaryExpression(Expression left, Expression right) : base(left, right)
         {
         }
 
-        public override async ValueTask<FluidValue> EvaluateAsync(TemplateContext context)
+        public override ValueTask<FluidValue> EvaluateAsync(TemplateContext context)
         {
-            var leftValue = await Left.EvaluateAsync(context);
-            var rightValue = await Right.EvaluateAsync(context);
+            static async ValueTask<FluidValue> Awaited(ValueTask<FluidValue> leftTask, ValueTask<FluidValue> rightTask)
+            {
+                var leftValue = await leftTask;
+                var rightValue = await rightTask;
 
-            return BooleanValue.Create(leftValue.ToBooleanValue() || rightValue.ToBooleanValue());
+                return BooleanValue.Create(leftValue.ToBooleanValue() || rightValue.ToBooleanValue());
+            }
+
+            var leftTask = Left.EvaluateAsync(context);
+            var rightTask = Right.EvaluateAsync(context);
+
+            if (leftTask.IsCompletedSuccessfully && rightTask.IsCompletedSuccessfully)
+            {
+                return BooleanValue.Create(leftTask.Result.ToBooleanValue() || rightTask.Result.ToBooleanValue());
+            }
+
+            return Awaited(leftTask, rightTask);
         }
     }
 }

Fluid/Ast/ElseIfStatement.cs

@@ -14,15 +14,50 @@ public ElseIfStatement(Expression condition, List<Statement> statements) : base(
 
         public Expression Condition { get; }
 
-        public override async ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
+        public override ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
         {
             // Process statements until next block or end of statements
-            for (var index = 0; index < _statements.Count; index++)
+            for (var i = 0; i < _statements.Count; i++)
             {
                 context.IncrementSteps();
 
-                var completion = await _statements[index].WriteToAsync(writer, encoder, context);
+                var task = _statements[i].WriteToAsync(writer, encoder, context);
+                if (!task.IsCompletedSuccessfully)
+                {
+                    return Awaited(task, i + 1, writer, encoder, context);
+                }
+
+                var completion = task.Result;
+                if (completion != Completion.Normal)
+                {
+                    // Stop processing the block statements
+                    // We return the completion to flow it to the outer loop
+                    return new ValueTask<Completion>(completion);
+                }
+            }
 
+            return new ValueTask<Completion>(Completion.Normal);
+        }
+
+        private async ValueTask<Completion> Awaited(
+            ValueTask<Completion> task,
+            int startIndex,
+            TextWriter writer,
+            TextEncoder encoder,
+            TemplateContext context)
+        {
+            var completion = await task;
+            if (completion != Completion.Normal)
+            {
+                // Stop processing the block statements
+                // We return the completion to flow it to the outer loop
+                return completion;
+            }
+            // Process statements until next block or end of statements
+            for (var index = startIndex; index < _statements.Count; index++)
+            {
+                context.IncrementSteps();
+                completion = await _statements[index].WriteToAsync(writer, encoder, context);
                 if (completion != Completion.Normal)
                 {
                     // Stop processing the block statements

Fluid/Ast/ElseStatement.cs

@@ -11,14 +11,53 @@ public ElseStatement(List<Statement> statements) : base(statements)
         {
         }
 
-        public override async ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
+        public override ValueTask<Completion> WriteToAsync(TextWriter writer, TextEncoder encoder, TemplateContext context)
         {
             for (var i = 0; i < _statements.Count; i++)
             {
                 context.IncrementSteps();
 
-                var statement = _statements[i];
-                var completion = await statement.WriteToAsync(writer, encoder, context);
+                var task = _statements[i].WriteToAsync(writer, encoder, context);
+
+                if (!task.IsCompletedSuccessfully)
+                {
+                    return Awaited(task, i + 1, writer, encoder, context);
+                }
+
+                var completion = task.Result;
+
+                if (completion != Completion.Normal)
+                {
+                    // Stop processing the block statements
+                    // We return the completion to flow it to the outer loop
+                    return new ValueTask<Completion>(completion);
+                }
+            }
+
+            return new ValueTask<Completion>(Completion.Normal);
+        }
+
+        private async ValueTask<Completion> Awaited(
+            ValueTask<Completion> task,
+            int startIndex,
+            TextWriter writer,
+            TextEncoder encoder,
+            TemplateContext context)
+        {
+            var completion = await task;
+
+            if (completion != Completion.Normal)
+            {
+                // Stop processing the block statements
+                // We return the completion to flow it to the outer loop
+                return completion;
+            }
+
+            for (var i = startIndex; i < _statements.Count; i++)
+            {
+                context.IncrementSteps();
+
+                completion = await _statements[i].WriteToAsync(writer, encoder, context);
 
                 if (completion != Completion.Normal)
                 {