unified: Add debug query for local scoping graph

shared/namebinding/codeql/namebinding/LocalNameBinding.qll

@@ -296,6 +296,31 @@ module LocalNameBinding<LocationSig Location, LocalNameBindingInputSig<Location>
     )
   }
 
+  /** Holds if `node` should be included in the debug tree. */
+  private signature predicate relevantNodeSig(AstNode node);
+
+  module DebugScopeGraph<relevantNodeSig/1 relevantNode> {
+    private string getANodeAnnotation(AstNode node) {
+      result =
+        "[scope=" +
+          strictconcat(string name |
+            declInScope(_, name, node) or implicitDeclInScope(name, node)
+          |
+            name, ","
+          ) + "]"
+    }
+
+    query predicate nodes(AstNode node, string key, string value) {
+      relevantNode(node) and
+      key = "semmle.label" and
+      value = node.toString() + concat(getANodeAnnotation(node))
+    }
+
+    query predicate edges(AstNode node1, AstNode node2) {
+      relevantNode(node2) and node2 = getParentForScoping(node1)
+    }
+  }
+
   /** Gets the immediately enclosing variable scope of `n`. */
   private Scope getEnclosingScope(AstNode n) {
     result = getParentForScoping(n)

unified/ql/lib/codeql/unified/internal/dev/debugScopeGraph.ql

@@ -0,0 +1,19 @@
+/**
+ * @name Debug scope graph
+ * @description Renders the graph used to perform local variable lookups
+ * @kind graph
+ * @id unified/debug-scope-graph
+ */
+
+private import unified
+private import codeql.unified.internal.Variables
+
+/**
+ * Holds if `node` should be shown in the graph.
+ */
+predicate relevantNode(AstNode node) {
+  // Match an ancestor node by location so its whole subtree is shown.
+  node.getParent*().getLocation().toString().matches("%test.swift@227:%")
+}
+
+import LocalNameBindingOutput::DebugScopeGraph<relevantNode/1>