Check whether each scriptblock being analysed has a process block that directly contains variable usage of $_ or $PSItem. Then when we encounted a parameter with ValueFromPipeline set, we consider whether we saw usage within a process block by automatic variable.

Author: liamjpeters

Rules/ReviewUnusedParameter.cs

@@ -98,6 +98,19 @@ public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
                 // find all declared parameters
                 IEnumerable<Ast> parameterAsts = scriptBlockAst.FindAll(oneAst => oneAst is ParameterAst, false);
 
+                // does the scriptblock have a process block where either $PSItem or $_ is referenced
+                bool hasProcessBlockWithPSItemOrUnderscore = false;
+                if (scriptBlockAst.ProcessBlock != null)
+                {
+                    IDictionary<string, int> processBlockVariableCount = GetVariableCount(scriptBlockAst.ProcessBlock);
+                    processBlockVariableCount.TryGetValue("_", out int underscoreVariableCount);
+                    processBlockVariableCount.TryGetValue("psitem", out int psitemVariableCount);
+                    if (underscoreVariableCount > 0 || psitemVariableCount > 0)
+                    {
+                        hasProcessBlockWithPSItemOrUnderscore = true;
+                    }
+                }
+
                 // list all variables
                 IDictionary<string, int> variableCount = GetVariableCount(scriptBlockAst);
 
@@ -108,18 +121,14 @@ public IEnumerable<DiagnosticRecord> AnalyzeScript(Ast ast, string fileName)
                         valFromPipelineAst => valFromPipelineAst is NamedAttributeArgumentAst namedAttrib && string.Equals(
                             namedAttrib.ArgumentName, "ValueFromPipeline",
                             StringComparison.OrdinalIgnoreCase
-                        ), 
+                        ),
                         false
                     );
-                    // If the parameter has the ValueFromPipeline attribute, check for usages of $_ or $PSItem
-                    if (valueFromPipeline?.GetValue() == true)
+                    // If the parameter has the ValueFromPipeline attribute and the scriptblock has a process block with
+                    // $_ or $PSItem usage, then the parameter is considered used
+                    if (valueFromPipeline?.GetValue() == true && hasProcessBlockWithPSItemOrUnderscore)
                     {
-                        variableCount.TryGetValue("_", out int underscoreVariableCount);
-                        variableCount.TryGetValue("psitem", out int psitemVariableCount);
-                        if (underscoreVariableCount > 0 || psitemVariableCount > 0)
-                        {
-                            continue;
-                        }
+                        continue;
                     }
 
                     // there should be at least two usages of the variable since the parameter declaration counts as one
@@ -240,7 +249,7 @@ public string GetSourceName()
         /// <param name="ast">The scriptblock ast to scan</param>
         /// <param name="data">Previously generated data. New findings are added to any existing dictionary if present</param>
         /// <returns>a dictionary including all variables in the scriptblock and their count</returns>
-        IDictionary<string, int> GetVariableCount(ScriptBlockAst ast, Dictionary<string, int> data = null)
+        IDictionary<string, int> GetVariableCount(Ast ast, Dictionary<string, int> data = null)
         {
             Dictionary<string, int> content = data;
             if (null == data)