feat(truncatehtml): gate void element preservation behind a feature

src/main/java/com/hubspot/jinjava/features/BuiltInFeatures.java

@@ -9,4 +9,5 @@ public interface BuiltInFeatures {
     "IGNORE_NESTED_INTERPRETATION_PARSE_ERRORS";
   String OUTPUT_UNDEFINED_VARIABLES_ERROR = "OUTPUT_UNDEFINED_VARIABLES_ERROR";
   String INTEGER_SET_TO_LONG_CONVERSION = "INTEGER_SET_TO_LONG_CONVERSION";
+  String PRESERVE_VOID_IN_TRUNCATE_HTML = "PRESERVE_VOID_IN_TRUNCATE_HTML";
 }

src/main/java/com/hubspot/jinjava/lib/filter/TruncateHtmlFilter.java

@@ -3,6 +3,7 @@
 import com.hubspot.jinjava.doc.annotations.JinjavaDoc;
 import com.hubspot.jinjava.doc.annotations.JinjavaParam;
 import com.hubspot.jinjava.doc.annotations.JinjavaSnippet;
+import com.hubspot.jinjava.features.BuiltInFeatures;
 import com.hubspot.jinjava.interpret.InvalidArgumentException;
 import com.hubspot.jinjava.interpret.JinjavaInterpreter;
 import com.hubspot.jinjava.interpret.TemplateError;
@@ -144,11 +145,20 @@ public Object filter(Object var, JinjavaInterpreter interpreter, String... args)
         killwords = BooleanUtils.toBoolean(args[2]);
       }
 
+      boolean preserveVoidElements = interpreter
+        .getConfig()
+        .getFeatures()
+        .isActive(
+          BuiltInFeatures.PRESERVE_VOID_IN_TRUNCATE_HTML,
+          interpreter.getContext()
+        );
+
       Document dom = Jsoup.parseBodyFragment((String) var);
       ContentTruncatingNodeVisitor visitor = new ContentTruncatingNodeVisitor(
         length,
         ends,
-        killwords
+        killwords,
+        preserveVoidElements
       );
       dom.select("body").traverse(visitor);
       dom.select("." + DELETE_MARKER_CLASS).remove();
@@ -165,13 +175,20 @@ private static class ContentTruncatingNodeVisitor implements NodeVisitor {
     private int textLen;
     private final String ending;
     private final boolean killwords;
+    private final boolean preserveVoidElements;
     private final Deque<Integer> keptVoidElementsAtEntry = new ArrayDeque<>();
     private int keptVoidElements;
 
-    ContentTruncatingNodeVisitor(int maxTextLen, String ending, boolean killwords) {
+    ContentTruncatingNodeVisitor(
+      int maxTextLen,
+      String ending,
+      boolean killwords,
+      boolean preserveVoidElements
+    ) {
       this.maxTextLen = maxTextLen;
       this.ending = ending;
       this.killwords = killwords;
+      this.preserveVoidElements = preserveVoidElements;
     }
 
     @Override
@@ -193,7 +210,7 @@ public void head(Node node, int depth) {
         } else {
           textLen += textContent.length();
         }
-      } else if (node instanceof Element el) {
+      } else if (preserveVoidElements && node instanceof Element el) {
         keptVoidElementsAtEntry.push(keptVoidElements);
         if (isVoidElement(el)) {
           if (textLen >= maxTextLen) {
@@ -207,15 +224,19 @@ public void head(Node node, int depth) {
 
     @Override
     public void tail(Node node, int depth) {
-      if (node instanceof Element el) {
-        boolean containsKeptVoidElement =
-          keptVoidElements > keptVoidElementsAtEntry.pop();
-        if (
-          !isVoidElement(el) && !containsKeptVoidElement && StringUtils.isBlank(el.text())
-        ) {
-          el.addClass(DELETE_MARKER_CLASS);
-        }
+      if (node instanceof Element el && shouldRemoveOnExit(el)) {
+        el.addClass(DELETE_MARKER_CLASS);
+      }
+    }
+
+    private boolean shouldRemoveOnExit(Element el) {
+      if (!preserveVoidElements) {
+        return StringUtils.isBlank(el.text());
       }
+      boolean containsKeptVoidElement = keptVoidElements > keptVoidElementsAtEntry.pop();
+      return (
+        !isVoidElement(el) && !containsKeptVoidElement && StringUtils.isBlank(el.text())
+      );
     }
 
     private static boolean isVoidElement(Element el) {

src/test/java/com/hubspot/jinjava/lib/filter/TruncateHtmlFilterTest.java

@@ -5,6 +5,12 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.io.Resources;
 import com.hubspot.jinjava.BaseInterpretingTest;
+import com.hubspot.jinjava.BaseJinjavaTest;
+import com.hubspot.jinjava.Jinjava;
+import com.hubspot.jinjava.features.BuiltInFeatures;
+import com.hubspot.jinjava.features.FeatureConfig;
+import com.hubspot.jinjava.features.FeatureStrategies;
+import com.hubspot.jinjava.interpret.JinjavaInterpreter;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import org.junit.Before;
@@ -13,10 +19,27 @@
 public class TruncateHtmlFilterTest extends BaseInterpretingTest {
 
   TruncateHtmlFilter filter;
+  JinjavaInterpreter preserveVoidInterpreter;
 
   @Before
   public void setup() {
     filter = new TruncateHtmlFilter();
+    preserveVoidInterpreter =
+      new Jinjava(
+        BaseJinjavaTest
+          .newConfigBuilder()
+          .withFeatureConfig(
+            FeatureConfig
+              .newBuilder()
+              .add(
+                BuiltInFeatures.PRESERVE_VOID_IN_TRUNCATE_HTML,
+                FeatureStrategies.ACTIVE
+              )
+              .build()
+          )
+          .build()
+      )
+        .newInterpreter();
   }
 
   @Test
@@ -82,7 +105,7 @@ public void itTakesKwargs() {
   public void itPreservesVoidElementsWhenContentIsUnderTheLimit() {
     String result = (String) filter.filter(
       "<p>Hey,<br>Great to hear!</p><p><img src=\"a.png\"></p>",
-      interpreter,
+      preserveVoidInterpreter,
       "255"
     );
     assertThat(result)
@@ -93,7 +116,7 @@ public void itPreservesVoidElementsWhenContentIsUnderTheLimit() {
   public void itPreservesVoidElementsBeforeTheTruncationPoint() {
     String result = (String) filter.filter(
       "<p>Hello<br>world, this is long text</p>",
-      interpreter,
+      preserveVoidInterpreter,
       "10",
       "...",
       "true"
@@ -105,7 +128,7 @@ public void itPreservesVoidElementsBeforeTheTruncationPoint() {
   public void itRemovesVoidElementsAfterTheTruncationPoint() {
     String result = (String) filter.filter(
       "<p>Hello world</p><p>more<br>text</p><img src=\"a.png\">",
-      interpreter,
+      preserveVoidInterpreter,
       "5",
       "...",
       "true"
@@ -117,7 +140,7 @@ public void itRemovesVoidElementsAfterTheTruncationPoint() {
   public void itPreservesSelfClosingBrTagsBeforeTheTruncationPoint() {
     String result = (String) filter.filter(
       "<p>Hey,<br/>Great to hear!</p>",
-      interpreter,
+      preserveVoidInterpreter,
       "255"
     );
     assertThat(result).isEqualTo("<p>Hey,\n <br>\n Great to hear!</p>");
@@ -127,7 +150,7 @@ public void itPreservesSelfClosingBrTagsBeforeTheTruncationPoint() {
   public void itRemovesSelfClosingBrTagsAfterTheTruncationPoint() {
     String result = (String) filter.filter(
       "<p>Hello world<br/>more text</p><br/>",
-      interpreter,
+      preserveVoidInterpreter,
       "5",
       "...",
       "true"
@@ -139,7 +162,7 @@ public void itRemovesSelfClosingBrTagsAfterTheTruncationPoint() {
   public void itPreservesVoidElementsWithExplicitClosingTagsBeforeTheTruncationPoint() {
     String result = (String) filter.filter(
       "<p><img src=\"a.png\" width=\"10\"></img>Great to hear!</p>",
-      interpreter,
+      preserveVoidInterpreter,
       "255"
     );
     assertThat(result).isEqualTo("<p><img src=\"a.png\" width=\"10\">Great to hear!</p>");
@@ -149,14 +172,36 @@ public void itPreservesVoidElementsWithExplicitClosingTagsBeforeTheTruncationPoi
   public void itRemovesVoidElementsWithExplicitClosingTagsAfterTheTruncationPoint() {
     String result = (String) filter.filter(
       "<p>Hello world</p><p><img src=\"a.png\" width=\"10\"></img></p>",
-      interpreter,
+      preserveVoidInterpreter,
       "5",
       "...",
       "true"
     );
     assertThat(result).isEqualTo("<p>Hello...</p>");
   }
 
+  @Test
+  public void itRemovesVoidElementsWhenFeatureIsInactive() {
+    String result = (String) filter.filter(
+      "<p>Hey,<br>Great to hear!</p><p><img src=\"a.png\"></p>",
+      interpreter,
+      "255"
+    );
+    assertThat(result).isEqualTo("<p>Hey,Great to hear!</p>");
+  }
+
+  @Test
+  public void itRemovesVoidElementsBeforeTheTruncationPointWhenFeatureIsInactive() {
+    String result = (String) filter.filter(
+      "<p>Hello<br>world, this is long text</p>",
+      interpreter,
+      "10",
+      "...",
+      "true"
+    );
+    assertThat(result).isEqualTo("<p>Helloworld...</p>");
+  }
+
   private static String fixture(String name) {
     try {
       return Resources.toString(Resources.getResource(name), StandardCharsets.UTF_8);