Update ParseFiles test for nested templates

src/TextTemplate/Template.cs

@@ -0,0 +1,73 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using Antlr4.Runtime;
+
+namespace TextTemplate;
+
+/// <summary>
+/// Represents a text template similar to Go's template.Template.
+/// </summary>
+public class Template
+{
+    private string _templateString = string.Empty;
+
+    /// <summary>
+    /// The template name.
+    /// </summary>
+    public string Name { get; }
+
+    private Template(string name)
+    {
+        Name = name;
+    }
+
+    /// <summary>
+    /// Creates a new Template with the given name.
+    /// </summary>
+    public static Template New(string name) => new(name);
+
+    /// <summary>
+    /// Parses the supplied template string and returns the Template instance.
+    /// </summary>
+    public Template Parse(string templateString)
+    {
+        if (templateString == null) throw new ArgumentNullException(nameof(templateString));
+        // Validate using the TemplateEngine so parsing rules remain consistent.
+        TemplateEngine.Validate(templateString);
+        _templateString = templateString;
+        return this;
+    }
+
+    /// <summary>
+    /// Reads the given files, combines their contents, and parses the result.
+    /// </summary>
+    public Template ParseFiles(params string[] filenames)
+    {
+        if (filenames == null) throw new ArgumentNullException(nameof(filenames));
+        var sb = new StringBuilder();
+        foreach (var file in filenames)
+        {
+            sb.Append(File.ReadAllText(file));
+        }
+        return Parse(sb.ToString());
+    }
+
+    /// <summary>
+    /// Executes the template using the provided dictionary.
+    /// </summary>
+    public string Execute(IDictionary<string, object> data)
+    {
+        return TemplateEngine.Process(_templateString, data);
+    }
+
+    /// <summary>
+    /// Executes the template using the public properties of <typeparamref name="T"/>.
+    /// </summary>
+    public string Execute<T>(T model)
+    {
+        return TemplateEngine.Process(_templateString, model);
+    }
+
+}

src/TextTemplate/TemplateEngine.cs

@@ -24,7 +24,7 @@
     {
         templateString = PreprocessWhitespace(templateString);
         templateString = PreprocessComments(templateString);
-        AntlrInputStream inputStream = new(templateString);
+        var inputStream = new AntlrInputStream(templateString);
         var lexer = new GoTextTemplateLexer(inputStream);
         var tokens = new CommonTokenStream(lexer);
         var parser = new GoTextTemplateParser(tokens);
@@ -35,6 +35,21 @@
         return visitor.Visit(tree);
     }
 
+    /// <summary>
+    /// Parses <paramref name="templateString"/> to ensure it contains valid syntax.
+    /// </summary>
+    public static void Validate(string templateString)
+    {
+        if (templateString == null) throw new ArgumentNullException(nameof(templateString));
+        templateString = PreprocessWhitespace(templateString);
+        templateString = PreprocessComments(templateString);
+        var inputStream = new AntlrInputStream(templateString);
+        var lexer = new GoTextTemplateLexer(inputStream);
+        var tokens = new CommonTokenStream(lexer);
+        var parser = new GoTextTemplateParser(tokens);
+        parser.template();
+    }
+
     /// <summary>
     /// Processes <paramref name="templateString"/> using the public properties
     /// and fields of <paramref name="model"/> as template variables.
@@ -142,7 +157,7 @@
                 if (args.Length == 0) return string.Empty;
                 string fmt = args[0]?.ToString() ?? string.Empty;
                 var rest = args.Skip(1).ToArray();
                 return SprintfFormatter.Format(fmt, rest);
             },
             ["html"] = args => System.Net.WebUtility.HtmlEncode(string.Concat(args.Select(a => a?.ToString()))),
             ["js"] = args => System.Text.Encodings.Web.JavaScriptEncoder.Default.Encode(string.Concat(args.Select(a => a?.ToString()))),
@@ -174,7 +189,7 @@
                     }
                     if (current is IDictionary dict)
                     {
                         current = dict[key];
                         continue;
                     }
                     current = null;

tests/TextTemplate.Tests/TemplateClassTests.cs

@@ -0,0 +1,41 @@
+using Shouldly;
+using TextTemplate;
+using Xunit;
+using System.IO;
+
+namespace TextTemplate.Tests;
+
+public class TemplateClassTests
+{
+    [Fact]
+    public void NewParseExecutePattern_Works()
+    {
+        var tmpl = Template.New("t").Parse("Hello {{ .Name }}! {{ range .Items }}{{ . }} {{ end }}");
+        var result = tmpl.Execute(new { Name = "Bob", Items = new[] { "a", "b" } });
+        result.ShouldBe("Hello Bob! a b ");
+    }
+
+    [Fact]
+    public void ParseFiles_ReadsAndParsesAllFiles()
+    {
+        var f1 = Path.GetTempFileName();
+        var f2 = Path.GetTempFileName();
+        var f3 = Path.GetTempFileName();
+        try
+        {
+            File.WriteAllText(f1, "{{define \"header\"}}Hello {{.Name}}{{end}}");
+            File.WriteAllText(f2, "{{define \"exclaim\"}}!{{end}}");
+            File.WriteAllText(f3, "{{template \"header\" .}}{{template \"exclaim\"}}");
+
+            var tmpl = Template.New("t").ParseFiles(f1, f2, f3);
+            var result = tmpl.Execute(new { Name = "Ann" });
+            result.ShouldBe("Hello Ann!");
+        }
+        finally
+        {
+            File.Delete(f1);
+            File.Delete(f2);
+            File.Delete(f3);
+        }
+    }
+}