Fix severity filtering while invoking script analyzer

Filters the rules based on their severity before passing them the AST for
analysis.

Prior to the fix, the severity filter was applied on diagnostic records.
This was inefficient as Invoke-ScriptAnalyzer would run all the rules
irrespective of the given severity and then filter the diagnostic records
to extract the results that corresponded to the given severity.

Author: Kapil Borle

Engine/ScriptAnalyzer.cs

@@ -1320,6 +1320,64 @@ private IEnumerable<DiagnosticRecord> AnalyzeFile(string filePath)
             return this.AnalyzeSyntaxTree(scriptAst, scriptTokens, filePath);
         }
 
+        private bool IsSeverityAllowed(IEnumerable<uint> allowedSeverities, IRule rule)
+        {
+            return severity == null 
+                || (allowedSeverities != null 
+                    && rule != null 
+                    && HasGetSeverity(rule) 
+                    && allowedSeverities.Contains((uint)rule.GetSeverity()));
+        }
+
+        IEnumerable<uint> GetAllowedSeveritiesInInt()
+        {
+            return severity != null 
+                ? severity.Select(item => (uint)Enum.Parse(typeof(DiagnosticSeverity), item, true)) 
+                : null;
+        }
+
+        bool HasMethod<T>(T obj, string methodName)
+        {
+            var type = obj.GetType();
+            return type.GetMethod(methodName) != null;
+        }
+
+        bool HasGetSeverity<T>(T obj)
+        {
+            return HasMethod<T>(obj, "GetSeverity");
+        }
+
+        bool IsRuleAllowed(IRule rule)
+        {
+            IEnumerable<uint> allowedSeverities = GetAllowedSeveritiesInInt();
+            bool includeRegexMatch = false;
+            bool excludeRegexMatch = false;
+            foreach (Regex include in includeRegexList)
+            {
+                if (include.IsMatch(rule.GetName()))
+                {
+                    includeRegexMatch = true;
+                    break;
+                }
+            }
+
+            foreach (Regex exclude in excludeRegexList)
+            {
+                if (exclude.IsMatch(rule.GetName()))
+                {
+                    excludeRegexMatch = true;
+                    break;
+                }
+            }
+
+            bool helpRule = String.Equals(rule.GetName(), "PSUseUTF8EncodingForHelpFile", StringComparison.OrdinalIgnoreCase);
+            bool includeSeverity = IsSeverityAllowed(allowedSeverities, rule);
+
+            return (includeRule == null || includeRegexMatch)
+                    && (excludeRule == null || !excludeRegexMatch)
+                    && IsSeverityAllowed(allowedSeverities, rule);
+        }
+
         /// <summary>
         /// Analyzes the syntax tree of a script file that has already been parsed.
         /// </summary>
@@ -1373,39 +1431,17 @@ public IEnumerable<DiagnosticRecord> AnalyzeSyntaxTree(
 
                 Helper.Instance.Tokens = scriptTokens;
             }
-
+          
             #region Run ScriptRules
             //Trim down to the leaf element of the filePath and pass it to Diagnostic Record
             string fileName = filePathIsNullOrWhiteSpace ? String.Empty : System.IO.Path.GetFileName(filePath);
-
             if (this.ScriptRules != null)
             {
                 var tasks = this.ScriptRules.Select(scriptRule => Task.Factory.StartNew(() =>
                 {
-                    bool includeRegexMatch = false;
-                    bool excludeRegexMatch = false;
-
-                    foreach (Regex include in includeRegexList)
-                    {
-                        if (include.IsMatch(scriptRule.GetName()))
-                        {
-                            includeRegexMatch = true;
-                            break;
-                        }
-                    }
-
-                    foreach (Regex exclude in excludeRegexList)
-                    {
-                        if (exclude.IsMatch(scriptRule.GetName()))
-                        {
-                            excludeRegexMatch = true;
-                            break;
-                        }
-                    }
-
                     bool helpRule = String.Equals(scriptRule.GetName(), "PSUseUTF8EncodingForHelpFile", StringComparison.OrdinalIgnoreCase);
 
-                    if ((includeRule == null || includeRegexMatch) && (excludeRule == null || !excludeRegexMatch))
+                    if (IsRuleAllowed(scriptRule))
                     {
                         List<object> result = new List<object>();
 
@@ -1475,25 +1511,7 @@ public IEnumerable<DiagnosticRecord> AnalyzeSyntaxTree(
             {
                 foreach (ITokenRule tokenRule in this.TokenRules)
                 {
-                    bool includeRegexMatch = false;
-                    bool excludeRegexMatch = false;
-                    foreach (Regex include in includeRegexList)
-                    {
-                        if (include.IsMatch(tokenRule.GetName()))
-                        {
-                            includeRegexMatch = true;
-                            break;
-                        }
-                    }
-                    foreach (Regex exclude in excludeRegexList)
-                    {
-                        if (exclude.IsMatch(tokenRule.GetName()))
-                        {
-                            excludeRegexMatch = true;
-                            break;
-                        }
-                    }
-                    if ((includeRule == null || includeRegexMatch) && (excludeRule == null || !excludeRegexMatch))
+                    if (IsRuleAllowed(tokenRule))
                     {
                         this.outputWriter.WriteVerbose(string.Format(CultureInfo.CurrentCulture, Strings.VerboseRunningMessage, tokenRule.GetName()));
 
@@ -1592,24 +1610,7 @@ public IEnumerable<DiagnosticRecord> AnalyzeSyntaxTree(
                     // Run all DSC Rules
                     foreach (IDSCResourceRule dscResourceRule in this.DSCResourceRules)
                     {
-                        bool includeRegexMatch = false;
-                        bool excludeRegexMatch = false;
-                        foreach (Regex include in includeRegexList)
-                        {
-                            if (include.IsMatch(dscResourceRule.GetName()))
-                            {
-                                includeRegexMatch = true;
-                                break;
-                            }
-                        }
-                        foreach (Regex exclude in excludeRegexList)
-                        {
-                            if (exclude.IsMatch(dscResourceRule.GetName()))
-                            {
-                                excludeRegexMatch = true;
-                            }
-                        }
-                        if ((includeRule == null || includeRegexMatch) && (excludeRule == null || !excludeRegexMatch))
+                        if (IsRuleAllowed(dscResourceRule))
                         {
                             this.outputWriter.WriteVerbose(string.Format(CultureInfo.CurrentCulture, Strings.VerboseRunningMessage, dscResourceRule.GetName()));
 
@@ -1646,8 +1647,7 @@ public IEnumerable<DiagnosticRecord> AnalyzeSyntaxTree(
 
                 foreach (ExternalRule exRule in this.ExternalRules)
                 {
-                    if ((includeRule == null || includeRule.Contains(exRule.GetName(), StringComparer.OrdinalIgnoreCase)) &&
-                        (excludeRule == null || !excludeRule.Contains(exRule.GetName(), StringComparer.OrdinalIgnoreCase)))
+                    if (IsRuleAllowed(exRule))
                     {
                         string ruleName = string.Format(CultureInfo.CurrentCulture, "{0}\\{1}", exRule.GetSourceName(), exRule.GetName());
                         this.outputWriter.WriteVerbose(string.Format(CultureInfo.CurrentCulture, Strings.VerboseRunningMessage, ruleName));
@@ -1676,15 +1676,6 @@ public IEnumerable<DiagnosticRecord> AnalyzeSyntaxTree(
             // Need to reverse the concurrentbag to ensure that results are sorted in the increasing order of line numbers
             IEnumerable<DiagnosticRecord> diagnosticsList = diagnostics.Reverse();
 
-            if (severity != null)
-            {
-                var diagSeverity = severity.Select(item => Enum.Parse(typeof(DiagnosticSeverity), item, true));
-                if (diagSeverity.Count() != 0)
-                {
-                    diagnosticsList = diagnostics.Where(item => diagSeverity.Contains(item.Severity));
-                }
-            }
-
             return this.suppressedOnly ?
                 suppressed.OfType<DiagnosticRecord>() :
                 diagnosticsList;