JS: Add PreCallGraphStep extension point

javascript/ql/src/semmle/javascript/dataflow/DataFlow.qll

@@ -23,6 +23,7 @@ private import internal.CallGraphs
 private import internal.FlowSteps as FlowSteps
 private import internal.DataFlowNode
 private import internal.AnalyzedParameters
+private import internal.PreCallGraphStep
 
 module DataFlow {
   /**

javascript/ql/src/semmle/javascript/dataflow/internal/PreCallGraphStep.qll

@@ -0,0 +1,135 @@
+/**
+ * Provides an extension point for contributing flow edges prior
+ * to call graph construction and type tracking.
+ */
+private import javascript
+
+private newtype TUnit = MkUnit()
+
+private class Unit extends TUnit {
+  string toString() { result = "unit" }
+}
+
+/**
+ * Internal extension point for adding flow edges prior to call graph construction
+ * and type tracking.
+ *
+ * Steps added here will be added to both `AdditionalFlowStep` and `AdditionalTypeTrackingStep`.
+ *
+ * Contributing steps that rely on type tracking will lead to negative recursion.
+ */
+class PreCallGraphStep extends Unit {
+  /**
+   * Holds if there is a step from `pred` to `succ`.
+   */
+  predicate step(DataFlow::Node pred, DataFlow::Node succ) { none() }
+
+  /**
+   * Holds if there is a step from `pred` into the `prop` property of `succ`.
+   */
+  predicate storeStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) { none() }
+
+  /**
+   * Holds if there is a step from the `prop` property of `pred` to `succ`.
+   */
+  predicate loadStep(DataFlow::Node pred, DataFlow::Node succ, string prop) { none() }
+
+  /**
+   * Holds if there is a step from the `prop` property of `pred` to the same property in `succ`.
+   */
+  predicate loadStoreStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) { none() }
+}
+
+module PreCallGraphStep {
+  /**
+   * Holds if there is a step from `pred` to `succ`.
+   */
+  cached
+  predicate step(DataFlow::Node pred, DataFlow::Node succ) {
+    any(PreCallGraphStep s).step(pred, succ)
+  }
+
+  /**
+   * Holds if there is a step from `pred` into the `prop` property of `succ`.
+   */
+  cached
+  predicate storeStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) {
+    any(PreCallGraphStep s).storeStep(pred, succ, prop)
+  }
+
+  /**
+   * Holds if there is a step from the `prop` property of `pred` to `succ`.
+   */
+  cached
+  predicate loadStep(DataFlow::Node pred, DataFlow::Node succ, string prop) {
+    any(PreCallGraphStep s).loadStep(pred, succ, prop)
+  }
+
+  /**
+   * Holds if there is a step from the `prop` property of `pred` to the same property in `succ`.
+   */
+  cached
+  predicate loadStoreStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) {
+    any(PreCallGraphStep s).loadStoreStep(pred, succ, prop)
+  }
+}
+
+private class NodeWithPreCallGraphStep extends DataFlow::Node {
+  NodeWithPreCallGraphStep() {
+    PreCallGraphStep::step(this, _)
+    or
+    PreCallGraphStep::storeStep(this, _, _)
+    or
+    PreCallGraphStep::loadStep(this, _, _)
+    or
+    PreCallGraphStep::loadStoreStep(this, _, _)
+  }
+}
+
+private class AdditionalFlowStepFromPreCallGraph extends NodeWithPreCallGraphStep,
+  DataFlow::AdditionalFlowStep {
+
+  override predicate step(DataFlow::Node pred, DataFlow::Node succ) {
+    pred = this and
+    PreCallGraphStep::step(this, succ)
+  }
+
+  override predicate storeStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) {
+    pred = this and
+    PreCallGraphStep::storeStep(this, succ, prop)
+  }
+
+  override predicate loadStep(DataFlow::Node pred, DataFlow::Node succ, string prop) {
+    pred = this and
+    PreCallGraphStep::loadStep(this, succ, prop)
+  }
+
+  override predicate loadStoreStep(DataFlow::Node pred, DataFlow::Node succ, string prop) {
+    pred = this and
+    PreCallGraphStep::loadStoreStep(this, succ, prop)
+  }
+}
+
+private class AdditionalTypeTrackingStepFromPreCallGraph extends NodeWithPreCallGraphStep,
+  DataFlow::AdditionalTypeTrackingStep {
+
+  override predicate step(DataFlow::Node pred, DataFlow::Node succ) {
+    pred = this and
+    PreCallGraphStep::step(this, succ)
+  }
+
+  override predicate storeStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) {
+    pred = this and
+    PreCallGraphStep::storeStep(this, succ, prop)
+  }
+
+  override predicate loadStep(DataFlow::Node pred, DataFlow::Node succ, string prop) {
+    pred = this and
+    PreCallGraphStep::loadStep(this, succ, prop)
+  }
+
+  override predicate loadStoreStep(DataFlow::Node pred, DataFlow::SourceNode succ, string prop) {
+    pred = this and
+    PreCallGraphStep::loadStoreStep(this, succ, prop)
+  }
+}