From c9c9e566b14c36291939747abcddc3b28f273adc Mon Sep 17 00:00:00 2001
From: Ellpeck <me@ellpeck.de>
Date: Mon, 22 Nov 2021 17:50:17 +0100
Subject: [PATCH] Throw an exception when text formatter macros resolve
 recursively too many times

---
 CHANGELOG.md                     | 1 +
 MLEM/Formatting/TextFormatter.cs | 5 +++++
 Tests/FontTests.cs               | 6 ++++++
 3 files changed, 12 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fad0db4..97e5aa9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ Improvements
 - Exposed Camera's RoundPosition
 - Exposed the epsilon value used by Camera
 - Added Padding.Empty
+- Throw an exception when text formatter macros resolve recursively too many times
 
 ### MLEM.Ui
 Additions
diff --git a/MLEM/Formatting/TextFormatter.cs b/MLEM/Formatting/TextFormatter.cs
index f7584c7..ad1fb9b 100644
--- a/MLEM/Formatting/TextFormatter.cs
+++ b/MLEM/Formatting/TextFormatter.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
@@ -114,6 +115,7 @@ namespace MLEM.Formatting {
         /// <returns>The final, recursively resolved string</returns>
         public string ResolveMacros(string s) {
             // resolve macros that resolve into macros
+            var rec = 0;
             bool matched;
             do {
                 matched = false;
@@ -124,6 +126,9 @@ namespace MLEM.Formatting {
                         return macro.Value(this, m, macro.Key);
                     });
                 }
+                rec++;
+                if (rec >= 16)
+                    throw new ArithmeticException($"A string resolved macros recursively too many times. Does it contain any conflicting macros?\n{s}");
             } while (matched);
             return s;
         }
diff --git a/Tests/FontTests.cs b/Tests/FontTests.cs
index 6ac1366..3ab2998 100644
--- a/Tests/FontTests.cs
+++ b/Tests/FontTests.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Text.RegularExpressions;
 using Microsoft.Xna.Framework;
 using Microsoft.Xna.Framework.Graphics;
@@ -107,6 +108,11 @@ namespace Tests {
             const string strg = "This text uses a bunch of non-breaking~spaces to see if macros work. Additionally, it uses a macro that resolves into a bunch of other macros and then, at the end, into <testmacro> text</c>.";
             const string goal = "This text uses a bunch of non-breaking\u00A0spaces to see if macros work. Additionally, it uses a macro that resolves into a bunch of other macros and then, at the end, into <c Blue>blue text</c>.";
             Assert.AreEqual(this.formatter.ResolveMacros(strg), goal);
+
+            // test recursive macros
+            this.formatter.Macros.Add(new Regex("<rec1>"), (f, m, r) => "<rec2>");
+            this.formatter.Macros.Add(new Regex("<rec2>"), (f, m, r) => "<rec1>");
+            Assert.Throws<ArithmeticException>(() => this.formatter.ResolveMacros("Test <rec1> string"));
         }
 
         [Test]