From 91dcc869374e9a6d37ad8f7caa584f20cbcb763a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?S=C3=A9bastien=20Ros?= <sebastienros@gmail.com>
Date: Tue, 20 Dec 2022 15:54:31 -0800
Subject: [PATCH] Concatenate arrays with single elements (#547)

#Fixes 542
---
 Fluid.Tests/ArrayFiltersTests.cs | 21 +++++++++++++++++++++
 Fluid/Filters/ArrayFilters.cs    | 31 +++++++++++++++++++++----------
 2 files changed, 42 insertions(+), 10 deletions(-)

diff --git a/Fluid.Tests/ArrayFiltersTests.cs b/Fluid.Tests/ArrayFiltersTests.cs
index 2b5b56f0..a504b581 100644
--- a/Fluid.Tests/ArrayFiltersTests.cs
+++ b/Fluid.Tests/ArrayFiltersTests.cs
@@ -109,6 +109,27 @@ public void Concat()
             Assert.Equal(6, result.Result.Enumerate(context).Count());
         }
 
+        [Fact]
+        public void ConcatSingleValue()
+        {
+            var input = new StringValue("a");
+
+            var arguments = new FilterArguments().Add(
+                new ArrayValue(new[] {
+                    new StringValue("1"),
+                    new StringValue("2"),
+                    new StringValue("3")
+                    })
+            );
+
+            var context = new TemplateContext();
+
+            var result = ArrayFilters.Concat(input, arguments, context);
+
+            Assert.Equal("a", result.Result.Enumerate(context).First().ToStringValue());
+            Assert.Equal(4, result.Result.Enumerate(context).Count());
+        }
+
         [Fact]
         public async Task Map()
         {
diff --git a/Fluid/Filters/ArrayFilters.cs b/Fluid/Filters/ArrayFilters.cs
index d61628b0..7d08e42c 100644
--- a/Fluid/Filters/ArrayFilters.cs
+++ b/Fluid/Filters/ArrayFilters.cs
@@ -49,26 +49,37 @@ public static ValueTask<FluidValue> Last(FluidValue input, FilterArguments argum
 
         public static ValueTask<FluidValue> Concat(FluidValue input, FilterArguments arguments, TemplateContext context)
         {
-            if (input.Type != FluidValues.Array)
-            {
-                return input;
-            }
+            var arg = arguments.At(0);
 
-            if (arguments.At(0).Type != FluidValues.Array)
+            if (input.Type != FluidValues.Array && arg.Type != FluidValues.Array)
             {
                 return input;
             }
-
+            
             var concat = new List<FluidValue>();
 
-            foreach(var item in input.Enumerate(context))
+            if (input.Type == FluidValues.Array)
+            {
+                foreach (var item in input.Enumerate(context))
+                {
+                    concat.Add(item);
+                }
+            }
+            else
             {
-                concat.Add(item);
+                concat.Add(input);
             }
 
-            foreach (var item in arguments.At(0).Enumerate(context))
+            if (arg.Type == FluidValues.Array)
+            {
+                foreach (var item in arg.Enumerate(context))
+                {
+                    concat.Add(item);
+                }
+            }
+            else
             {
-                concat.Add(item);
+                concat.Add(arg);
             }
 
             return new ArrayValue(concat);