Brace a member body that holds only comments or directives [patch]

CodeBlocker.Test/TemplateTests.cs

@@ -648,6 +648,71 @@ public void ABodyThatWritesOnlyBlankLinesRendersAsAnEmptyBlock(int newLines)
 		Assert.AreEqual("public void M() { }\n", Render(method));
 	}
 
+	[TestMethod]
+	public void ABodyThatWritesOnlyALineCommentIsBraced() =>
+		// "void M() // nothing to reset" has no body at all (CS1002).
+		Assert.AreEqual(
+			"void M()\n{\n\t// nothing to reset\n}\n",
+			Render(new MethodTemplate
+			{
+				Type = "void",
+				Name = "M",
+				BodyFactory = codeBlocker => codeBlocker.WriteLine("// nothing to reset"),
+			}));
+
+	[TestMethod]
+	public void ABodyThatWritesOnlyLineCommentsIsBraced() =>
+		Assert.AreEqual(
+			"void M()\n{\n\t// a\n\t// b\n}\n",
+			Render(new MethodTemplate
+			{
+				Type = "void",
+				Name = "M",
+				BodyFactory = codeBlocker =>
+				{
+					codeBlocker.WriteLine("// a");
+					codeBlocker.WriteLine("// b");
+				},
+			}));
+
+	[TestMethod]
+	public void AConstructorBodyThatWritesOnlyALineCommentIsBraced() =>
+		Assert.AreEqual(
+			"C()\n{\n\t// no state\n}\n",
+			Render(new ConstructorTemplate
+			{
+				Name = "C",
+				BodyFactory = codeBlocker => codeBlocker.WriteLine("// no state"),
+			}));
+
+	[TestMethod]
+	public void ABodyThatWritesOnlyAnEmptyPragmaScopeIsBraced() =>
+		Assert.AreEqual(
+			"void M()\n{\n\t#pragma warning disable CS0168\n\t#pragma warning restore CS0168\n}\n",
+			Render(new MethodTemplate
+			{
+				Type = "void",
+				Name = "M",
+				BodyFactory = codeBlocker =>
+				{
+					using PragmaScope pragma = new(codeBlocker, "CS0168");
+				},
+			}));
+
+	[TestMethod]
+	[DataRow("=> x;")]
+	[DataRow("{ }")]
+	[DataRow("=> x; // trailing")]
+	public void AOneLineBodyWithCodeStaysOnTheDeclarationLine(string body) =>
+		Assert.AreEqual(
+			$"int M() {body}\n",
+			Render(new MethodTemplate
+			{
+				Type = "int",
+				Name = "M",
+				BodyFactory = codeBlocker => codeBlocker.WriteLine(body),
+			}));
+
 	[TestMethod]
 	public void AnExpressionBodyBetweenBlankLinesStaysOnTheDeclarationLine() =>
 		Assert.AreEqual(

CodeBlocker/Templates/TemplateRendering.cs

@@ -294,6 +294,20 @@ internal static void WriteBody(CodeBlocker codeBlocker, Action<CodeBlocker>? bod
 			return;
 		}
 
+		// A comment or a directive is not a body either: written after the declaration it leaves the
+		// member with none, so a body made only of them is wrapped in braces instead. A generator
+		// writing "// no fields to reset" in place of an empty loop would otherwise emit CS1002.
+		if (!HasCode(lines))
+		{
+			codeBlocker.WriteLine();
+			using (new Scope(codeBlocker))
+			{
+				SpliceFragment(codeBlocker, body);
+			}
+
+			return;
+		}
+
 		if (contentLines.Length == 1)
 		{
 			// An expression body stays on the declaration line.
@@ -372,6 +386,27 @@ internal static void WriteExpressionBody(CodeBlocker codeBlocker, Action<CodeBlo
 		}
 	}
 
+	/// <summary>
+	/// Reports whether any line of a fragment holds code: something other than a line comment or a
+	/// preprocessor directive.
+	/// </summary>
+	/// <param name="lines">The lines of a fragment, as <see cref="SplitLines"/> returns them.</param>
+	/// <returns><see langword="true"/> if at least one line has code on it.</returns>
+	private static bool HasCode(string[] lines)
+	{
+		int[] codeEnds = FindCodeEnds(lines);
+		for (int i = 0; i < lines.Length; i++)
+		{
+			string code = lines[i][..codeEnds[i]].Trim();
+			if (code.Length != 0 && code[0] != '#')
+			{
+				return true;
+			}
+		}
+
+		return false;
+	}
+
 	/// <summary>
 	/// Finds where the code on each line ends: at the start of the line comment the line ends in,
 	/// or at the end of the line when it has none.