PS: Flow through pipelines.

Author: MathiasVP

powershell/ql/lib/semmle/code/powershell/ast/internal/Pipeline.qll

@@ -28,4 +28,11 @@ class Pipeline extends Expr, TPipeline {
   Expr getAComponent() { result = this.getComponent(_) }
 
   int getNumberOfComponents() { result = getRawAst(this).(Raw::Pipeline).getNumberOfComponents() }
+
+  Expr getLastComponent() {
+    exists(int i |
+      result = this.getComponent(i) and
+      not exists(this.getComponent(i + 1))
+    )
+  }
 }

powershell/ql/lib/semmle/code/powershell/controlflow/CfgNodes.qll

@@ -859,6 +859,8 @@ module ExprNodes {
     ExprCfgNode getComponent(int i) { e.hasCfgChild(e.getComponent(i), this, result) }
 
     ExprCfgNode getAComponent() { result = this.getComponent(_) }
+
+    ExprCfgNode getLastComponent() { e.hasCfgChild(e.getLastComponent(), this, result) }
   }
 
   private class PipelineChainChildMapping extends ExprChildMapping, PipelineChain {

powershell/ql/lib/semmle/code/powershell/dataflow/internal/DataFlowPrivate.qll

@@ -140,6 +140,8 @@ module LocalFlow {
     or
     nodeFrom.asExpr() = nodeTo.asExpr().(CfgNodes::ExprNodes::ArrayExprCfgNode)
     or
+    nodeTo.asExpr().(CfgNodes::ExprNodes::PipelineCfgNode).getLastComponent() = nodeFrom.asExpr()
+    or
     exists(CfgNodes::ExprCfgNode e |
       e = nodeFrom.(AstNode).getCfgNode() and
       isReturned(e) and