Add an exception for a missing node name to setRoots. Test the results of some basic setRoots operations

Author: AngledLuffa

src/edu/stanford/nlp/semgraph/semgrex/ssurgeon/SetRoots.java

@@ -26,8 +26,13 @@ public SetRoots(List<String> newRootNames) {
   @Override
   public boolean evaluate(SemanticGraph sg, SemgrexMatcher sm) {
     Set<IndexedWord> newRoots = new LinkedHashSet<>();
-    for (String name : newRootNames)
-      newRoots.add(getNamedNode(name, sm));
+    for (String name : newRootNames) {
+      IndexedWord root = getNamedNode(name, sm);
+      if (root == null) {
+        throw new SsurgeonRuntimeException("Ssurgeon rule tried to set root to " + name + " but that name does not exist in the semgrex results");
+      }
+      newRoots.add(root);
+    }
     if (newRoots.equals(sg.getRoots()))
       return false;
     sg.setRoots(newRoots);

test/src/edu/stanford/nlp/semgraph/semgrex/ssurgeon/SsurgeonTest.java

@@ -434,6 +434,68 @@ public void readXMLKillIncomingEdges() {
     assertEquals(2, cutSG.getRoots().size());
   }
 
+  /**
+   * Check the result of rearranging an edge and then setting the root to a new label
+   */
+  @Test
+  public void readXMLSetRoots() {
+    Ssurgeon inst = Ssurgeon.inst();
+
+    String cut = String.join(newline,
+                             "<ssurgeon-pattern-list>",
+                             "  <ssurgeon-pattern>",
+                             "    <uid>38</uid>",
+                             "    <notes>Test the effects of setRoots on a simple change</notes>",
+                             "    <semgrex>" + XMLUtils.escapeXML("{word:A}=a >dep=dep {word:B}=b") + "</semgrex>",
+                             "    <edit-list>removeNamedEdge -edge dep</edit-list>",
+                             "    <edit-list>addEdge -gov b -dep a -reln dep</edit-list>",
+                             "    <edit-list>setRoots b</edit-list>",
+                             "  </ssurgeon-pattern>",
+                             "</ssurgeon-pattern-list>");
+    List<SsurgeonPattern> patterns = inst.readFromString(cut);
+    assertEquals(patterns.size(), 1);
+    SsurgeonPattern rearrange = patterns.get(0);
+
+    // Test a two node only version
+    SemanticGraph sg = SemanticGraph.valueOf("[A-1 dep> B-2]");
+    SemanticGraph newSG = rearrange.iterate(sg);
+    SemanticGraph expected = SemanticGraph.valueOf("[B-2 dep> A-1]");
+    assertEquals(expected, newSG);
+  }
+
+
+  /**
+   * Check that a readable exception is thrown if the expected node doesn't exist for setRoots
+   */
+  @Test
+  public void readXMLSetRootsException() {
+    Ssurgeon inst = Ssurgeon.inst();
+
+    String cut = String.join(newline,
+                             "<ssurgeon-pattern-list>",
+                             "  <ssurgeon-pattern>",
+                             "    <uid>38</uid>",
+                             "    <notes>Remove all incoming edges for a node</notes>",
+                             "    <semgrex>" + XMLUtils.escapeXML("{word:A}=a >dep~dep {word:B}=b") + "</semgrex>",
+                             "    <edit-list>removeNamedEdge -edge dep</edit-list>",
+                             "    <edit-list>addEdge -gov b -dep a -reln dep</edit-list>",
+                             "    <edit-list>setRoots c</edit-list>",
+                             "  </ssurgeon-pattern>",
+                             "</ssurgeon-pattern-list>");
+    List<SsurgeonPattern> patterns = inst.readFromString(cut);
+    assertEquals(patterns.size(), 1);
+    SsurgeonPattern rearrange = patterns.get(0);
+
+    // Test a two node only version
+    SemanticGraph sg = SemanticGraph.valueOf("[A-1 dep> B-2]");
+    try {
+      SemanticGraph newSG = rearrange.iterate(sg);
+      throw new AssertionError("Expected a specific exception SsurgeonRuntimeException here");
+    } catch (SsurgeonRuntimeException e) {
+      // yay
+    }
+  }
+
   /**
    * Simple test of an Ssurgeon edit script.  This instances a simple semantic graph,
    * a semgrex pattern, and then the resulting actions over the named nodes in the