improve performance of filter expression validation

Author: tonerdo

src/coverlet.core/Coverage.cs

@@ -30,6 +30,7 @@ public void PrepareModules()
         {
             string[] modules = InstrumentationHelper.GetCoverableModules(_module);
             string[] excludedFiles =  InstrumentationHelper.GetExcludedFiles(_rules);
+            _filters = _filters?.Where(f => InstrumentationHelper.IsValidFilterExpression(f)).ToArray();
 
             foreach (var module in modules)
             {

src/coverlet.core/Helpers/InstrumentationHelper.cs

@@ -81,6 +81,38 @@ public static void DeleteHitsFile(string path)
             RetryHelper.Retry(() => File.Delete(path), retryStrategy, 10);
         }
 
+        public static bool IsValidFilterExpression(string filter)
+        {
+            if (filter == null)
+                return false;
+
+            if (!filter.StartsWith("["))
+                return false;
+
+            if (!filter.Contains("]"))
+                return false;
+
+            if (filter.Count(f => f == '[') > 1)
+                return false;
+
+            if (filter.Count(f => f == ']') > 1)
+                return false;
+
+            if (filter.IndexOf(']') < filter.IndexOf('['))
+                return false;
+
+            if (filter.IndexOf(']') - filter.IndexOf('[') == 1)
+                return false;
+
+            if (filter.EndsWith("]"))
+                return false;
+
+            if (new Regex(@"[^\w*]").IsMatch(filter.Replace(".", "").Replace("[", "").Replace("]", "")))
+                return false;
+
+            return true;
+        }
+
         public static bool IsModuleExcluded(string module, string[] filters)
         {
             if (filters == null)
@@ -91,9 +123,6 @@ public static bool IsModuleExcluded(string module, string[] filters)
 
             foreach (var filter in filters)
             {
-                if (!IsValidFilterExpression(filter))
-                    continue;
-
                 string modulePattern = filter.Substring(1, filter.IndexOf(']') - 1);
                 string typePattern = filter.Substring(filter.IndexOf(']') + 1);
 
@@ -116,9 +145,6 @@ public static bool IsTypeExcluded(string module, string type, string[] filters)
 
             foreach (var filter in filters)
             {
-                if (!IsValidFilterExpression(filter))
-                    continue;
-
                 string typePattern = filter.Substring(filter.IndexOf(']') + 1);
                 string modulePattern = filter.Substring(1, filter.IndexOf(']') - 1);
 
@@ -191,35 +217,6 @@ TimeSpan retryStrategy()
             return retryStrategy;
         }
 
-        private static bool IsValidFilterExpression(string filter)
-        {
-            if (!filter.StartsWith("["))
-                return false;
-
-            if (!filter.Contains("]"))
-                return false;
-
-            if (filter.Count(f => f == '[') > 1)
-                return false;
-
-            if (filter.Count(f => f == ']') > 1)
-                return false;
-
-            if (filter.IndexOf(']') < filter.IndexOf('['))
-                return false;
-
-            if (filter.IndexOf(']') - filter.IndexOf('[') == 1)
-                return false;
-
-            if (filter.EndsWith("]"))
-                return false;
-
-            if (new Regex(@"[^\w*]").IsMatch(filter.Replace(".", "").Replace("[", "").Replace("]", "")))
-                return false;
-
-            return true;
-        }
-
         private static string WildcardToRegex(string pattern)
         {
             return "^" + Regex.Escape(pattern).

test/coverlet.core.tests/Helpers/InstrumentationHelperTests.cs

@@ -50,6 +50,21 @@ public void TestCopyCoverletDependency()
             Directory.Delete(directory.FullName, true);
         }
 
+        [Fact]
+        public void TestIsValidFilterExpression()
+        {
+            Assert.True(InstrumentationHelper.IsValidFilterExpression("[*]*"));
+            Assert.True(InstrumentationHelper.IsValidFilterExpression("[*]*core"));
+            Assert.True(InstrumentationHelper.IsValidFilterExpression("[assembly]*"));
+            Assert.True(InstrumentationHelper.IsValidFilterExpression("[*]type"));
+            Assert.True(InstrumentationHelper.IsValidFilterExpression("[assembly]type"));
+            Assert.False(InstrumentationHelper.IsValidFilterExpression("[*]"));
+            Assert.False(InstrumentationHelper.IsValidFilterExpression("[-]*"));
+            Assert.False(InstrumentationHelper.IsValidFilterExpression("*"));
+            Assert.False(InstrumentationHelper.IsValidFilterExpression("]["));
+            Assert.False(InstrumentationHelper.IsValidFilterExpression(null));
+        }
+
         [Fact]
         public void TestDontCopyCoverletDependency()
         {