Add error message when saving an incomplete schema

extensions/wikidata/module/langs/translation-en.json

@@ -41,7 +41,8 @@
                 "reset-button": "Reset",
                 "save-button": "Save",
                 "close-button": "Close",
-                "unsaved-changes": "There are unsaved changes. Close anyway?"
+                "unsaved-changes": "There are unsaved changes. Close anyway?",
+                "incomplete-schema-could-not-be-saved": "Your schema is incomplete so it cannot be saved yet."
         },
         "wikidata-preview": {
                 "new-id": "new item"

extensions/wikidata/module/scripts/dialogs/schema-alignment-dialog.js

@@ -84,7 +84,10 @@ SchemaAlignmentDialog._save = function(onDone) {
         self._hasUnsavedChanges = false;
 
         if (onDone) onDone();
-      }
+      },
+      onError: function(e) {
+        alert($.i18n._('wikidata-schema')["incomplete-schema-could-not-be-saved"]);
+      },
     }
   );
 };

extensions/wikidata/src/org/openrefine/wikidata/commands/CommandUtilities.java

@@ -0,0 +1,32 @@
+package org.openrefine.wikidata.commands;
+
+import java.io.IOException;
+import java.io.Writer;
+
+import javax.servlet.http.HttpServletResponse;
+
+import org.json.JSONWriter;
+
+public class CommandUtilities {
+    
+    /**
+     * Helper introduced to ease returning error messages from a response. Curiously
+     * this is not part of {@link Command}: the respond method uses the "status" JSON
+     * key instead of the "code" one required by the JS code.
+     * 
+     * @param response
+     * @param errorMessage
+     * @throws IOException 
+     */
+    public static void respondError(HttpServletResponse response, String errorMessage)
+            throws IOException {
+        Writer w = response.getWriter();
+        JSONWriter writer = new JSONWriter(w);
+        writer.object();
+        writer.key("code"); writer.value("error");
+        writer.key("message"); writer.value(errorMessage);
+        writer.endObject();
+        w.flush();
+        w.close();
+    }
+}

extensions/wikidata/src/org/openrefine/wikidata/commands/PreviewWikibaseSchemaCommand.java

@@ -42,6 +42,7 @@ import org.openrefine.wikidata.qa.QAWarningStore;
 import org.openrefine.wikidata.schema.WikibaseSchema;
 import org.openrefine.wikidata.updates.ItemUpdate;
 import org.openrefine.wikidata.utils.FirstLinesExtractor;
+import static org.openrefine.wikidata.commands.CommandUtilities.respondError;
 
 import com.google.refine.browsing.Engine;
 import com.google.refine.commands.Command;
@@ -66,14 +67,14 @@ public class PreviewWikibaseSchemaCommand extends Command {
                 try {
                     schema = WikibaseSchema.reconstruct(jsonString);
                 } catch (JSONException e) {
-                    respond(response, "error", "Wikibase schema could not be parsed.");
+                    respondError(response, e.toString());
                     return;
                 }
             } else {
                 schema = (WikibaseSchema) project.overlayModels.get("wikibaseSchema");
             }
             if (schema == null) {
-                respond(response, "error", "No Wikibase schema provided.");
+                respondError(response, "No schema provided.");
                 return;
             }
 

extensions/wikidata/src/org/openrefine/wikidata/commands/SaveWikibaseSchemaCommand.java

@@ -34,6 +34,7 @@ import org.json.JSONException;
 import org.json.JSONObject;
 import org.openrefine.wikidata.operations.SaveWikibaseSchemaOperation;
 import org.openrefine.wikidata.schema.WikibaseSchema;
+import static org.openrefine.wikidata.commands.CommandUtilities.respondError;
 
 import com.google.refine.commands.Command;
 import com.google.refine.model.AbstractOperation;
@@ -52,7 +53,7 @@ public class SaveWikibaseSchemaCommand extends Command {
 
             String jsonString = request.getParameter("schema");
             if (jsonString == null) {
-                respond(response, "error", "No Wikibase schema provided.");
+                respondError(response, "No Wikibase schema provided.");
                 return;
             }
 
@@ -65,8 +66,12 @@ public class SaveWikibaseSchemaCommand extends Command {
             performProcessAndRespond(request, response, project, process);
 
         } catch (JSONException e) {
-            respond(response, "error", "Wikibase schema could not be parsed.");
+            // We do not use respondException here because this is an expected
+            // exception which happens every time a user tries to save an incomplete
+            // schema - the exception should not be logged.
+            respondError(response, "Invalid Wikibase schema provided.");
         } catch (Exception e) {
+            // This is an unexpected exception, so we log it.
             respondException(response, e);
         }
     }

extensions/wikidata/src/org/openrefine/wikidata/schema/WikibaseSchema.java

@@ -186,7 +186,7 @@ public class WikibaseSchema implements OverlayModel {
         return reconstruct(o.toString());
     }    
     
-    static public WikibaseSchema reconstruct(String json) {
+    static public WikibaseSchema reconstruct(String json) throws JSONException {
         ObjectMapper mapper = new ObjectMapper();
         try {
             return mapper.readValue(json, WikibaseSchema.class);

extensions/wikidata/tests/src/org/openrefine/wikidata/commands/SaveWikibaseSchemaCommandTest.java

@@ -51,4 +51,15 @@ public class SaveWikibaseSchemaCommandTest extends SchemaCommandTest {
 
         assertTrue(writer.toString().contains("\"ok\""));
     }
+    
+    @Test
+    public void testInvalidSchema() throws ServletException, IOException {
+        String schemaJson = "{\"itemDocuments\":[{\"statementGroups\":[{\"statements\":[]}],"
+                +"\"nameDescs\":[]}],\"wikibasePrefix\":\"http://www.wikidata.org/entity/\"}";
+        
+        when(request.getParameter("schema")).thenReturn(schemaJson);
+        command.doPost(request, response);
+        
+        assertTrue(writer.toString().contains("\"error\""));
+    }
 }

extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WbItemVariableTest.java

@@ -78,4 +78,6 @@ public class WbItemVariableTest extends WbVariableTest<ItemIdValue> {
         JacksonSerializationTest.canonicalSerialization(WbExpression.class, variable,
                 "{\"type\":\"wbitemvariable\",\"columnName\":\"column A\"}");
     }
+
+    // TODO: test with column reconciled against different identifier space
 }

extensions/wikidata/tests/src/org/openrefine/wikidata/schema/WikibaseSchemaTest.java

@@ -52,6 +52,8 @@ import org.wikidata.wdtk.datamodel.interfaces.StatementRank;
 import org.wikidata.wdtk.datamodel.interfaces.StringValue;
 import org.wikidata.wdtk.datamodel.interfaces.TimeValue;
 
+import com.fasterxml.jackson.databind.exc.InvalidDefinitionException;
+
 import com.google.refine.browsing.Engine;
 import com.google.refine.model.Project;
 import com.google.refine.tests.RefineTest;
@@ -132,6 +134,13 @@ public class WikibaseSchemaTest extends RefineTest {
         expected.add(update2);
         assertEquals(expected, updates);
     }
+    
+    @Test(expectedExceptions = JSONException.class)
+    public void testDeserializeEmpty() throws JSONException {
+        String schemaJson = "{\"itemDocuments\":[{\"statementGroups\":[{\"statements\":[]}],"
+                +"\"nameDescs\":[]}],\"wikibasePrefix\":\"http://www.wikidata.org/entity/\"}";
+        WikibaseSchema.reconstruct(schemaJson);
+    }
 
     @Test
     public void testEvaluateRespectsFacets()