Add error handling and test for regex timeouts (#107)

Author: costin-zaharia-sonarsource

sonar-text-dotnet/src/SonarLint.Secrets.DotNet.UnitTests/DotNetOnly/RegexMatcherTest_NoJavaTests.cs

@@ -43,7 +43,7 @@ woijwoj w woijw e
 
             var actual = testSubject.FindIn(input);
 
-            actual.Count().Should().Be(2);
+            actual.Count.Should().Be(2);
 
             actual.First().StartIndex.Should().Be(9);
             actual.First().Length.Should().Be(3);
@@ -53,5 +53,19 @@ woijwoj w woijw e
             actual.Last().Length.Should().Be(6);
             actual.Last().Text.Should().Be("abcdef");
         }
+
+        [TestMethod]
+        public void Find_RegexTimeout_DoesNotThrow()
+        {
+            const string pattern = @"([a-z]*)*";
+            var input = string.Join("", Enumerable.Repeat("a", 10_000_000));
+            var testSubject = new RegexMatcher(pattern);
+
+            // With this input the timeout is reached and an exception is thrown.
+            // This test ensures that the exception is not propagated further.
+            var actual = testSubject.FindIn(input);
+
+            actual.Count.Should().Be(0);
+        }
     }
 }

sonar-text-dotnet/src/SonarLint.Secrets.DotNet/Rules/Matching/RegexMatcher.cs

@@ -35,13 +35,19 @@ public RegexMatcher(string stringPattern)
 
         public List<Match> FindIn(string input)
         {
-            List<Match> matches = new List<Match>();
-
-            foreach (MatchResult matchResult in pattern.Matches(input))
+            var matches = new List<Match>();
+            try
+            {
+                foreach (MatchResult matchResult in pattern.Matches(input))
+                {
+                    // Note: hard-coded assumption that the text to highlight is in the second group (index = 1)
+                    var group = matchResult.Groups[1];
+                    matches.Add(new Match(group.Value, group.Index, group.Length));
+                }
+            }
+            catch (RegexMatchTimeoutException)
             {
-                // Note: hard-coded assumption that the text to highlight is in the second group (index = 1)
-                var group = matchResult.Groups[1];
-                matches.Add(new Match(group.Value, group.Index, group.Length));
+                return matches;
             }
 
             return matches;