Merge pull request #1110 from HubSpot/fix-npe-type-map

More gracefully handle null keys/values in map resolver

src/main/java/com/hubspot/jinjava/el/TypeConvertingMapELResolver.java

@@ -23,8 +23,18 @@ public Object getValue(ELContext context, Object base, Object property) {
 
     if (base instanceof Map && !((Map) base).isEmpty()) {
       Iterator<?> iterator = ((Map) base).keySet().iterator();
-      if (iterator.hasNext()) {
-        Class<?> keyClass = iterator.next().getClass();
+      Class<?> keyClass = null;
+      while (iterator.hasNext()) {
+        Object nextObject = iterator.next();
+        if (nextObject != null) {
+          keyClass = nextObject.getClass();
+          break;
+        }
+      }
+
+      if (keyClass == null) {
+        value = ((Map) base).get(property);
+      } else {
         try {
           value = ((Map) base).get(TYPE_CONVERTER.convert(property, keyClass));
           if (value != null) {

src/test/java/com/hubspot/jinjava/el/TypeConvertingMapELResolverTest.java

@@ -0,0 +1,60 @@
+package com.hubspot.jinjava.el;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.google.common.collect.ImmutableMap;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.Before;
+import org.junit.Test;
+
+public class TypeConvertingMapELResolverTest {
+  private TypeConvertingMapELResolver typeConvertingMapELResolver;
+
+  @Before
+  public void setup() {
+    typeConvertingMapELResolver = new TypeConvertingMapELResolver(false);
+  }
+
+  @Test
+  public void itResolvesProperties() {
+    Map<String, String> values = ImmutableMap.of("1", "value1", "2", "value2");
+    assertThat(typeConvertingMapELResolver.getValue(new JinjavaELContext(), values, "2"))
+      .isEqualTo("value2");
+  }
+
+  @Test
+  public void itConvertsPropertyClassWhenResolvingProperty() {
+    Map<String, String> values = ImmutableMap.of("1", "value1", "2", "value2");
+    assertThat(typeConvertingMapELResolver.getValue(new JinjavaELContext(), values, 1))
+      .isEqualTo("value1");
+  }
+
+  @Test
+  public void itHandlesNullKeyValuesWhenResolvingProperty() {
+    Map<String, String> values = new HashMap<>();
+    values.put(null, "nullValue");
+    values.put("1", "value1");
+    values.put("2", "value2");
+    assertThat(typeConvertingMapELResolver.getValue(new JinjavaELContext(), values, 1))
+      .isEqualTo("value1");
+  }
+
+  @Test
+  public void itHandlesMapWithOnlyNullKey() {
+    Map<String, String> values = new HashMap<>();
+    values.put(null, "nullValue");
+    assertThat(typeConvertingMapELResolver.getValue(new JinjavaELContext(), values, 1))
+      .isEqualTo(null);
+  }
+
+  @Test
+  public void itResolvesNullPropertyValue() {
+    Map<String, String> values = new HashMap<>();
+    values.put(null, "nullValue");
+    values.put("1", "value1");
+    values.put("2", "value2");
+    assertThat(typeConvertingMapELResolver.getValue(new JinjavaELContext(), values, null))
+      .isEqualTo("nullValue");
+  }
+}