Fix CallExprCfgNode.getKeywordArgument

This predicate now produces results.

Author: hmac

ruby/ql/lib/codeql/ruby/controlflow/CfgNodes.qll

@@ -320,7 +320,11 @@ module ExprNodes {
 
     /** Gets the the keyword argument whose key is `keyword` of this call. */
     final ExprCfgNode getKeywordArgument(string keyword) {
-      e.hasCfgChild(e.getKeywordArgument(keyword), this, result)
+      exists(PairCfgNode n |
+        e.hasCfgChild(e.getAnArgument(), this, n) and
+        n.getKey().getExpr().(SymbolLiteral).getValueText() = keyword and
+        result = n.getValue()
+      )
     }
 
     /** Gets the number of arguments of this call. */
@@ -426,6 +430,21 @@ module ExprNodes {
     ParenthesizedExprCfgNode() { this.getExpr() instanceof ParenthesizedExpr }
   }
 
+  private class PairChildMapping extends ExprChildMapping, Pair {
+    override predicate relevantChild(Expr e) { e = this.getKey() or e = this.getValue() }
+  }
+
+  /** A control-flow node that wraps a `Pair` AST expression. */
+  class PairCfgNode extends ExprCfgNode {
+    override PairChildMapping e;
+
+    final override Pair getExpr() { result = ExprCfgNode.super.getExpr() }
+
+    final ExprCfgNode getKey() { e.hasCfgChild(e.getKey(), this, result) }
+
+    final ExprCfgNode getValue() { e.hasCfgChild(e.getValue(), this, result) }
+  }
+
   /** A control-flow node that wraps a `VariableReadAccess` AST expression. */
   class VariableReadAccessCfgNode extends ExprCfgNode {
     override VariableReadAccess e;

ruby/ql/test/library-tests/controlflow/graph/Nodes.expected

@@ -319,3 +319,5 @@ positionalArguments
 | raise.rb:161:7:161:14 | call to raise | raise.rb:161:13:161:14 | "" |
 | raise.rb:168:5:168:12 | call to raise | raise.rb:168:11:168:12 | "" |
 keywordArguments
+| cfg.html.erb:6:9:6:58 | call to stylesheet_link_tag | media | cfg.html.erb:6:54:6:58 | "all" |
+| cfg.html.erb:12:11:12:33 | call to link_to | id | cfg.html.erb:12:31:12:33 | "a" |