Throw an exception when text formatter macros resolve recursively too many times

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

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;
         }

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]