fix: surface errors instead of silent failure in restricted .NET contexts (issue #581)

source/Handlebars.Test/Issues/Issue581Tests.cs

@@ -0,0 +1,120 @@
+using System;
+using System.IO;
+using Xunit;
+
+namespace HandlebarsDotNet.Test
+{
+    /// <summary>
+    /// Regression tests for GitHub issue #581:
+    /// Handlebars.Net fails silently in .NET 8 Windows Service context.
+    /// Templates produced no output and threw no exceptions.
+    /// Root cause: broad exception swallowing in observable collection publish paths
+    /// could prevent helper/template registrations from propagating in restricted
+    /// runtime environments, causing silent empty output.
+    /// </summary>
+    public class Issue581Tests
+    {
+        [Fact]
+        public void BasicCompileAndRender_NeverSilentlyFails()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("Hello {{name}}!");
+            var result = template(new { name = "World" });
+            Assert.Equal("Hello World!", result);
+        }
+
+        [Fact]
+        public void CompileWithTextReader_ProducesOutput()
+        {
+            var h = Handlebars.Create();
+            using var reader = new StringReader("Hello {{name}}!");
+            var template = h.Compile(reader);
+            using var writer = new StringWriter();
+            template(writer, new { name = "World" }, null);
+            Assert.Equal("Hello World!", writer.ToString());
+        }
+
+        [Fact]
+        public void RegisteredHelper_IsInvokedDuringRender()
+        {
+            var h = Handlebars.Create();
+            h.RegisterHelper("greet", (writer, context, arguments) =>
+            {
+                writer.WriteSafeString($"Hello {arguments[0]}");
+            });
+
+            var template = h.Compile("{{greet name}}");
+            var result = template(new { name = "World" });
+            Assert.Equal("Hello World", result);
+        }
+
+        [Fact]
+        public void RegisteredTemplate_IsResolvedAsPartial()
+        {
+            var h = Handlebars.Create();
+            h.RegisterTemplate("greeting", "Hello {{name}}");
+
+            var template = h.Compile("{{> greeting}}");
+            var result = template(new { name = "World" });
+            Assert.Equal("Hello World", result);
+        }
+
+        [Fact]
+        public void MultipleProperties_AreAllRendered()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("{{first}} {{last}}");
+            var result = template(new { first = "John", last = "Doe" });
+            Assert.Equal("John Doe", result);
+        }
+
+        [Fact]
+        public void NestedObject_PropertyAccess_Succeeds()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("{{person.name}}");
+            var result = template(new { person = new { name = "World" } });
+            Assert.Equal("World", result);
+        }
+
+        [Fact]
+        public void BlockHelper_IfElse_ProducesOutput()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("{{#if show}}yes{{else}}no{{/if}}");
+            Assert.Equal("yes", template(new { show = true }));
+            Assert.Equal("no", template(new { show = false }));
+        }
+
+        [Fact]
+        public void SharedEnvironment_CompileAndRender_NeverSilentlyFails()
+        {
+            var h = Handlebars.Create();
+            var shared = h.CreateSharedEnvironment();
+
+            var template = shared.Compile("Hello {{name}}!");
+            var result = template(new { name = "World" });
+            Assert.Equal("Hello World!", result);
+        }
+
+        [Fact]
+        public void EmptyTemplate_ProducesEmptyString_NotNull()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("");
+            var result = template(new { });
+            // An empty template should produce an empty string, not null
+            Assert.NotNull(result);
+            Assert.Equal("", result);
+        }
+
+        [Fact]
+        public void StaticText_Template_ProducesOutput()
+        {
+            var h = Handlebars.Create();
+            var template = h.Compile("static text only");
+            var result = template(new { });
+            Assert.Equal("static text only", result);
+        }
+    }
+}