Python: Refactor argumentRoutingTest.ql to be more generic

I checked to see that the tests still works. If I deleted the `arg5`
annotation, it got failures:

```diff
diff --git a/python/ql/test/experimental/dataflow/coverage/argumentPassing.py b/python/ql/test/experimental/dataflow/coverage/argumentPassing.py
index e218bdd..71816c1e01 100644
--- a/python/ql/test/experimental/dataflow/coverage/argumentPassing.py
+++ b/python/ql/test/experimental/dataflow/coverage/argumentPassing.py
@@ -46,7 +46,7 @@ def argument_passing(
     c,
     d=arg4,  #$ arg4 func=argument_passing
     *,
-    e=arg5,  #$ arg5 func=argument_passing
+    e=arg5,
     f,
     **g,
 ):
diff --git a/python/ql/test/experimental/dataflow/coverage/argumentRoutingTest.expected b/python/ql/test/experimental/dataflow/coverage/argumentRoutingTest.expected
index e69de29..22037a40c3 100644
--- a/python/ql/test/experimental/dataflow/coverage/argumentRoutingTest.expected
+++ b/python/ql/test/experimental/dataflow/coverage/argumentRoutingTest.expected
@@ -0,0 +1,2 @@
+| argumentPassing.py:49:7:49:10 | ControlFlowNode for arg5 | Unexpected result: arg5= |
+| argumentPassing.py:49:7:49:10 | ControlFlowNode for arg5 | Unexpected result: func=argument_passing |
```

Author: RasmusWL

python/ql/test/experimental/dataflow/coverage/argumentRoutingTest.ql

@@ -46,209 +46,48 @@ class Argument1RoutingConfig extends DataFlow::Configuration {
   override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
 }
 
-class Argument2RoutingTest extends RoutingTest {
-  Argument2RoutingTest() { this = "Argument2RoutingTest" }
+// for argument 2 and up, we use a generic approach. Change `maxNumArgs` below if we
+// need to increase the maximum number of arguments.
+private int maxNumArgs() { result = 7 }
 
-  override string flowTag() { result = "arg2" }
+class RestArgumentRoutingTest extends RoutingTest {
+  int argNumber;
 
-  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
-    exists(Argument2RoutingConfig cfg | cfg.hasFlow(source, sink))
-  }
-}
-
-/**
- * A configuration to check routing of arguments through magic methods.
- */
-class Argument2RoutingConfig extends DataFlow::Configuration {
-  Argument2RoutingConfig() { this = "Argument2RoutingConfig" }
-
-  override predicate isSource(DataFlow::Node node) {
-    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg2"
-  }
-
-  override predicate isSink(DataFlow::Node node) {
-    exists(CallNode call |
-      call.getFunction().(NameNode).getId() = "SINK2" and
-      node.(DataFlow::CfgNode).getNode() = call.getAnArg()
-    )
-  }
-
-  /**
-   * We want to be able to use `arg` in a sequence of calls such as `func(kw=arg); ... ; func(arg)`.
-   * Use-use flow lets the argument to the first call reach the sink inside the second call,
-   * making it seem like we handle all cases even if we only handle the last one.
-   * We make the test honest by preventing flow into source nodes.
-   */
-  override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
-}
-
-class Argument3RoutingTest extends RoutingTest {
-  Argument3RoutingTest() { this = "Argument3RoutingTest" }
-
-  override string flowTag() { result = "arg3" }
-
-  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
-    exists(Argument3RoutingConfig cfg | cfg.hasFlow(source, sink))
-  }
-}
-
-/**
- * A configuration to check routing of arguments through magic methods.
- */
-class Argument3RoutingConfig extends DataFlow::Configuration {
-  Argument3RoutingConfig() { this = "Argument3RoutingConfig" }
-
-  override predicate isSource(DataFlow::Node node) {
-    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg3"
-  }
-
-  override predicate isSink(DataFlow::Node node) {
-    exists(CallNode call |
-      call.getFunction().(NameNode).getId() = "SINK3" and
-      node.(DataFlow::CfgNode).getNode() = call.getAnArg()
-    )
-  }
-
-  /**
-   * We want to be able to use `arg` in a sequence of calls such as `func(kw=arg); ... ; func(arg)`.
-   * Use-use flow lets the argument to the first call reach the sink inside the second call,
-   * making it seem like we handle all cases even if we only handle the last one.
-   * We make the test honest by preventing flow into source nodes.
-   */
-  override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
-}
-
-class Argument4RoutingTest extends RoutingTest {
-  Argument4RoutingTest() { this = "Argument4RoutingTest" }
-
-  override string flowTag() { result = "arg4" }
-
-  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
-    exists(Argument4RoutingConfig cfg | cfg.hasFlow(source, sink))
-  }
-}
-
-/**
- * A configuration to check routing of arguments through magic methods.
- */
-class Argument4RoutingConfig extends DataFlow::Configuration {
-  Argument4RoutingConfig() { this = "Argument4RoutingConfig" }
-
-  override predicate isSource(DataFlow::Node node) {
-    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg4"
-  }
-
-  override predicate isSink(DataFlow::Node node) {
-    exists(CallNode call |
-      call.getFunction().(NameNode).getId() = "SINK4" and
-      node.(DataFlow::CfgNode).getNode() = call.getAnArg()
-    )
+  RestArgumentRoutingTest() {
+    argNumber in [2 .. maxNumArgs()] and
+    this = "Argument" + argNumber + "RoutingTest"
   }
 
-  /**
-   * We want to be able to use `arg` in a sequence of calls such as `func(kw=arg); ... ; func(arg)`.
-   * Use-use flow lets the argument to the first call reach the sink inside the second call,
-   * making it seem like we handle all cases even if we only handle the last one.
-   * We make the test honest by preventing flow into source nodes.
-   */
-  override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
-}
-
-class Argument5RoutingTest extends RoutingTest {
-  Argument5RoutingTest() { this = "Argument5RoutingTest" }
-
-  override string flowTag() { result = "arg5" }
+  override string flowTag() { result = "arg" + argNumber }
 
   override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
-    exists(Argument5RoutingConfig cfg | cfg.hasFlow(source, sink))
-  }
-}
-
-/**
- * A configuration to check routing of arguments through magic methods.
- */
-class Argument5RoutingConfig extends DataFlow::Configuration {
-  Argument5RoutingConfig() { this = "Argument5RoutingConfig" }
-
-  override predicate isSource(DataFlow::Node node) {
-    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg5"
-  }
-
-  override predicate isSink(DataFlow::Node node) {
-    exists(CallNode call |
-      call.getFunction().(NameNode).getId() = "SINK5" and
-      node.(DataFlow::CfgNode).getNode() = call.getAnArg()
+    exists(RestArgumentRoutingConfig cfg | cfg.getArgNumber() = argNumber |
+      cfg.hasFlow(source, sink)
     )
   }
-
-  /**
-   * We want to be able to use `arg` in a sequence of calls such as `func(kw=arg); ... ; func(arg)`.
-   * Use-use flow lets the argument to the first call reach the sink inside the second call,
-   * making it seem like we handle all cases even if we only handle the last one.
-   * We make the test honest by preventing flow into source nodes.
-   */
-  override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
-}
-
-class Argument6RoutingTest extends RoutingTest {
-  Argument6RoutingTest() { this = "Argument6RoutingTest" }
-
-  override string flowTag() { result = "arg6" }
-
-  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
-    exists(Argument6RoutingConfig cfg | cfg.hasFlow(source, sink))
-  }
 }
 
 /**
  * A configuration to check routing of arguments through magic methods.
  */
-class Argument6RoutingConfig extends DataFlow::Configuration {
-  Argument6RoutingConfig() { this = "Argument6RoutingConfig" }
+class RestArgumentRoutingConfig extends DataFlow::Configuration {
+  int argNumber;
 
-  override predicate isSource(DataFlow::Node node) {
-    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg6"
+  RestArgumentRoutingConfig() {
+    argNumber in [2 .. maxNumArgs()] and
+    this = "Argument" + argNumber + "RoutingConfig"
   }
 
-  override predicate isSink(DataFlow::Node node) {
-    exists(CallNode call |
-      call.getFunction().(NameNode).getId() = "SINK6" and
-      node.(DataFlow::CfgNode).getNode() = call.getAnArg()
-    )
-  }
-
-  /**
-   * We want to be able to use `arg` in a sequence of calls such as `func(kw=arg); ... ; func(arg)`.
-   * Use-use flow lets the argument to the first call reach the sink inside the second call,
-   * making it seem like we handle all cases even if we only handle the last one.
-   * We make the test honest by preventing flow into source nodes.
-   */
-  override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
-}
-
-class Argument7RoutingTest extends RoutingTest {
-  Argument7RoutingTest() { this = "Argument7RoutingTest" }
-
-  override string flowTag() { result = "arg7" }
-
-  override predicate relevantFlow(DataFlow::Node source, DataFlow::Node sink) {
-    exists(Argument7RoutingConfig cfg | cfg.hasFlow(source, sink))
-  }
-}
-
-/**
- * A configuration to check routing of arguments through magic methods.
- */
-class Argument7RoutingConfig extends DataFlow::Configuration {
-  Argument7RoutingConfig() { this = "Argument7RoutingConfig" }
+  /** Gets the argument number this configuration is for. */
+  int getArgNumber() { result = argNumber }
 
   override predicate isSource(DataFlow::Node node) {
-    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg7"
+    node.(DataFlow::CfgNode).getNode().(NameNode).getId() = "arg" + argNumber
   }
 
   override predicate isSink(DataFlow::Node node) {
     exists(CallNode call |
-      call.getFunction().(NameNode).getId() = "SINK7" and
+      call.getFunction().(NameNode).getId() = "SINK" + argNumber and
       node.(DataFlow::CfgNode).getNode() = call.getAnArg()
     )
   }
@@ -259,5 +98,5 @@ class Argument7RoutingConfig extends DataFlow::Configuration {
    * making it seem like we handle all cases even if we only handle the last one.
    * We make the test honest by preventing flow into source nodes.
    */
-  override predicate isBarrierIn(DataFlow::Node node) { isSource(node) }
+  override predicate isBarrierIn(DataFlow::Node node) { this.isSource(node) }
 }