Revise ExternalFlow and FlowSummaryImpl API used for test generation

Author: smowton

java/ql/src/semmle/code/java/dataflow/ExternalFlow.qll

@@ -415,19 +415,25 @@ predicate summaryModel(
   string namespace, string type, boolean subtypes, string name, string signature, string ext,
   string input, string output, string kind
 ) {
-  exists(string row |
-    summaryModel(row) and
-    row.splitAt(";", 0) = namespace and
-    row.splitAt(";", 1) = type and
-    row.splitAt(";", 2) = subtypes.toString() and
-    subtypes = [true, false] and
-    row.splitAt(";", 3) = name and
-    row.splitAt(";", 4) = signature and
-    row.splitAt(";", 5) = ext and
-    row.splitAt(";", 6) = input and
-    row.splitAt(";", 7) = output and
-    row.splitAt(";", 8) = kind
-  )
+  summaryModel(namespace, type, subtypes, name, signature, ext, input, output, kind, _)
+}
+
+/** Holds if a summary model `row` exists for the given parameters. */
+predicate summaryModel(
+  string namespace, string type, boolean subtypes, string name, string signature, string ext,
+  string input, string output, string kind, string row
+) {
+  summaryModel(row) and
+  row.splitAt(";", 0) = namespace and
+  row.splitAt(";", 1) = type and
+  row.splitAt(";", 2) = subtypes.toString() and
+  subtypes = [true, false] and
+  row.splitAt(";", 3) = name and
+  row.splitAt(";", 4) = signature and
+  row.splitAt(";", 5) = ext and
+  row.splitAt(";", 6) = input and
+  row.splitAt(";", 7) = output and
+  row.splitAt(";", 8) = kind
 }
 
 private predicate relevantPackage(string package) {

java/ql/src/semmle/code/java/dataflow/internal/FlowSummaryImpl.qll

@@ -643,7 +643,14 @@ module Private {
       )
     }
 
-    private predicate interpretSpec(string spec, int idx, SummaryComponentStack stack) {
+    /**
+     * Holds if `spec` specifies summary component stack `stack`.
+     */
+    predicate interpretSpec(string spec, SummaryComponentStack stack) {
+      interpretSpec(spec, 0, stack)
+    }
+
+    predicate interpretSpec(string spec, int idx, SummaryComponentStack stack) {
       exists(string c |
         relevantSpec(spec) and
         specLength(spec, idx + 1) and