From bd0abfe3db24f995ecc53213def32c26ef27c78c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9l=C3=A8ne=20Martin?= <ln@getodk.org>
Date: Wed, 31 Jan 2024 21:57:21 -0800
Subject: [PATCH] Use placeholder root for empty external secondary instance

---
 .../model/instance/ExternalDataInstance.java  | 14 +++--
 .../ExternalSecondaryInstanceParseTest.java   | 59 +++++++++++++------
 .../org/javarosa/xform/parse/header_only.csv  |  1 +
 3 files changed, 53 insertions(+), 21 deletions(-)
 create mode 100644 src/test/resources/org/javarosa/xform/parse/header_only.csv

diff --git a/src/main/java/org/javarosa/core/model/instance/ExternalDataInstance.java b/src/main/java/org/javarosa/core/model/instance/ExternalDataInstance.java
index 4e43a800b..422926273 100644
--- a/src/main/java/org/javarosa/core/model/instance/ExternalDataInstance.java
+++ b/src/main/java/org/javarosa/core/model/instance/ExternalDataInstance.java
@@ -1,9 +1,5 @@
 package org.javarosa.core.model.instance;
 
-import java.io.DataInputStream;
-import java.io.DataOutputStream;
-import java.io.FileNotFoundException;
-import java.io.IOException;
 import org.javarosa.core.model.instance.geojson.GeoJsonExternalInstance;
 import org.javarosa.core.reference.InvalidReferenceException;
 import org.javarosa.core.reference.ReferenceManager;
@@ -18,6 +14,11 @@
 import org.slf4j.LoggerFactory;
 import org.xmlpull.v1.XmlPullParserException;
 
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+
 // This is still a work in progress.
 
 public class ExternalDataInstance extends DataInstance {
@@ -62,6 +63,11 @@ public static ExternalDataInstance build(String instanceSrc, String instanceId)
         TreeElement root;
         try {
             root = parseExternalInstance(instanceSrc, instanceId);
+
+            // Avoid parse error for missing name and label refs if a select is built on an empty placeholder file
+            if (!root.hasChildren()) {
+                root = PLACEHOLDER_ROOT;
+            }
         } catch (FileNotFoundException | InvalidReferenceException e) {
             logger.info("External instance not found, falling back to placeholder");
             root = PLACEHOLDER_ROOT;
diff --git a/src/test/java/org/javarosa/xform/parse/ExternalSecondaryInstanceParseTest.java b/src/test/java/org/javarosa/xform/parse/ExternalSecondaryInstanceParseTest.java
index ff1f356d1..949172299 100644
--- a/src/test/java/org/javarosa/xform/parse/ExternalSecondaryInstanceParseTest.java
+++ b/src/test/java/org/javarosa/xform/parse/ExternalSecondaryInstanceParseTest.java
@@ -1,5 +1,23 @@
 package org.javarosa.xform.parse;
 
+import org.javarosa.core.model.FormDef;
+import org.javarosa.core.model.SelectChoice;
+import org.javarosa.core.model.condition.EvaluationContext;
+import org.javarosa.core.model.data.helper.Selection;
+import org.javarosa.core.model.instance.AbstractTreeElement;
+import org.javarosa.core.model.instance.TreeReference;
+import org.javarosa.core.test.FormParseInit;
+import org.javarosa.core.test.Scenario;
+import org.javarosa.core.util.externalizable.DeserializationException;
+import org.javarosa.xpath.expr.XPathPathExpr;
+import org.javarosa.xpath.parser.XPathSyntaxException;
+import org.junit.Test;
+
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.List;
+
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.nullValue;
 import static org.hamcrest.MatcherAssert.assertThat;
@@ -22,23 +40,6 @@
 import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
 
-import java.io.FileNotFoundException;
-import java.io.IOException;
-import java.nio.file.Path;
-import java.util.List;
-import org.javarosa.core.model.FormDef;
-import org.javarosa.core.model.SelectChoice;
-import org.javarosa.core.model.condition.EvaluationContext;
-import org.javarosa.core.model.data.helper.Selection;
-import org.javarosa.core.model.instance.AbstractTreeElement;
-import org.javarosa.core.model.instance.TreeReference;
-import org.javarosa.core.test.FormParseInit;
-import org.javarosa.core.test.Scenario;
-import org.javarosa.core.util.externalizable.DeserializationException;
-import org.javarosa.xpath.expr.XPathPathExpr;
-import org.javarosa.xpath.parser.XPathSyntaxException;
-import org.junit.Test;
-
 public class ExternalSecondaryInstanceParseTest {
 
     //region Parsing of different file types into external secondary instances
@@ -132,6 +133,30 @@ public void xformParseException_whenItemsetConfiguresValueOrLabelNotInExternalIn
         }
     }
 
+    @Test
+    public void csvSecondaryInstanceWithHeaderOnly_parsesWithoutError() throws IOException, XFormParser.ParseException {
+        configureReferenceManagerCorrectly();
+
+        Scenario scenario = Scenario.init("Some form", html(
+            head(
+                title("Some form"),
+                model(
+                    mainInstance(t("data id=\"some-form\"",
+                        t("first")
+                    )),
+
+                    t("instance id=\"external-csv\" src=\"jr://file-csv/header_only.csv\""),
+
+                    bind("/data/first").type("string")
+                )
+            ),
+            body(
+                select1Dynamic("/data/first", "instance('external-csv')/root/item")
+            )));
+
+        assertThat(scenario.choicesOf("/data/first").size(), is(0));
+    }
+
     @Test
     public void formWithExternalSecondaryXMLInstance_ShouldSerializeAndDeserialize() throws IOException, DeserializationException, XFormParser.ParseException {
         configureReferenceManagerCorrectly();
diff --git a/src/test/resources/org/javarosa/xform/parse/header_only.csv b/src/test/resources/org/javarosa/xform/parse/header_only.csv
new file mode 100644
index 000000000..7b342d489
--- /dev/null
+++ b/src/test/resources/org/javarosa/xform/parse/header_only.csv
@@ -0,0 +1 @@
+name,label,first_name,last_name
\ No newline at end of file