ReviewUnusedParameter: Do not trigger when MyInvocation.BoundParameters or PSCmdlet.MyInvocation.BoundParameters is used (#1520)

* Enhance ReviewUnusedParameter to bail out if $MyInvocation.BoundParmaeters encountered

* Account for $PSCmdlet.MyInvocation.BoundParameters

* Optmised the way we find bound parameters reference with in script block

* Address review feedback

* Remove unnecessary casting

* - Label boolean parameter
- Add pester tests

Co-authored-by: Manigandan Jegannathan <jegannat@deshaw.com>

Author: jegannathanmaniganadan

Rules/ReviewUnusedParameter.cs

@@ -36,6 +36,12 @@ public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
 
             foreach (ScriptBlockAst scriptBlockAst in scriptBlockAsts)
             {
+                // bail out if PS bound parameter used.
+                if (scriptBlockAst.Find(IsBoundParametersReference, searchNestedScriptBlocks: false) != null)
+                {
+                    continue;
+                }
+
                 // find all declared parameters
                 IEnumerable<Ast> parameterAsts = scriptBlockAst.FindAll(oneAst => oneAst is ParameterAst, false);
 
@@ -45,12 +51,6 @@ public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
                     .GroupBy(variableName => variableName, StringComparer.OrdinalIgnoreCase)
                     .ToDictionary(variableName => variableName.Key, variableName => variableName.Count(), StringComparer.OrdinalIgnoreCase);
 
-                // all bets are off if the script uses PSBoundParameters
-                if (variableCount.ContainsKey("PSBoundParameters"))
-                {
-                    continue;
-                }
-
                 foreach (ParameterAst parameterAst in parameterAsts)
                 {
                     // there should be at least two usages of the variable since the parameter declaration counts as one
@@ -72,6 +72,47 @@ public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
             }
         }
 
+        /// <summary>
+        /// Checks for PS bound parameter reference.
+        /// </summary>
+        /// <param name="ast">AST to be analyzed. This should be non-null</param>
+        /// <returns>Boolean true indicating that given AST has PS bound parameter reference, otherwise false</returns>
+        private static bool IsBoundParametersReference(Ast ast)
+        {
+            // $PSBoundParameters
+            if (ast is VariableExpressionAst variableAst
+                && variableAst.VariablePath.UserPath.Equals("PSBoundParameters", StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+
+            if (ast is MemberExpressionAst memberAst
+                && memberAst.Member is StringConstantExpressionAst memberStringAst
+                && memberStringAst.Value.Equals("BoundParameters", StringComparison.OrdinalIgnoreCase))
+            {
+                // $MyInvocation.BoundParameters
+                if (memberAst.Expression is VariableExpressionAst veAst
+                    && veAst.VariablePath.UserPath.Equals("MyInvocation", StringComparison.OrdinalIgnoreCase))
+                {
+                    return true;
+                }
+
+                // $PSCmdlet.MyInvocation.BoundParameters
+                if (memberAst.Expression is MemberExpressionAst meAstNested)
+                {
+                    if (meAstNested.Expression is VariableExpressionAst veAstNested
+                        && veAstNested.VariablePath.UserPath.Equals("PSCmdlet", StringComparison.OrdinalIgnoreCase)
+                        && meAstNested.Member is StringConstantExpressionAst sceAstNested
+                        && sceAstNested.Value.Equals("MyInvocation", StringComparison.OrdinalIgnoreCase))
+                    {
+                        return true;
+                    }
+                }
+            }
+
+            return false;
+        }
+
         /// <summary>
         /// GetName: Retrieves the name of this rule.
         /// </summary>

Tests/Rules/ReviewUnusedParameter.tests.ps1

@@ -59,6 +59,18 @@ Describe "ReviewUnusedParameter" {
             $Violations.Count | Should -Be 0
         }
 
+        It "has no violations when using MyInvocation.BoundParameters" {
+            $ScriptDefinition = 'function Bound { param ($Param1) $splat = $MyInvocation.BoundParameters; Get-Foo @splat }'
+            $Violations = Invoke-ScriptAnalyzer -ScriptDefinition $ScriptDefinition -IncludeRule $RuleName
+            $Violations.Count | Should -Be 0
+        }
+
+        It "has no violations when using PSCmdlet.MyInvocation.BoundParameters" {
+            $ScriptDefinition = 'function Bound { param ($Param1) $splat = $PSCmdlet.MyInvocation.BoundParameters; Get-Foo @splat }'
+            $Violations = Invoke-ScriptAnalyzer -ScriptDefinition $ScriptDefinition -IncludeRule $RuleName
+            $Violations.Count | Should -Be 0
+        }
+
         It "has no violations when parameter is called in child scope" -skip {
             $ScriptDefinition = 'function foo { param ($Param1) function Child { $Param1 } }'
             $Violations = Invoke-ScriptAnalyzer -ScriptDefinition $ScriptDefinition -IncludeRule $RuleName