Update TruncateHtmlFilter to execute jinjava before truncating

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.interpret.DeferredValueException;
 import com.hubspot.jinjava.interpret.InvalidArgumentException;
 import com.hubspot.jinjava.interpret.JinjavaInterpreter;
 import com.hubspot.jinjava.interpret.TemplateError;
@@ -141,7 +142,21 @@ public Object filter(Object var, JinjavaInterpreter interpreter, String... args)
         killwords = BooleanUtils.toBoolean(args[2]);
       }
 
-      Document dom = Jsoup.parseBodyFragment((String) var);
+      int numDeferredTokensStart = interpreter.getContext().getDeferredTokens().size();
+
+      String val;
+      try (
+        JinjavaInterpreter.InterpreterScopeClosable ignored = interpreter.enterScope()
+      ) {
+        val = interpreter.renderFlat((String) var);
+        if (
+          interpreter.getContext().getDeferredTokens().size() > numDeferredTokensStart
+        ) {
+          throw new DeferredValueException("Deferred in TruncateHtmlFilter");
+        }
+      }
+
+      Document dom = Jsoup.parseBodyFragment(val);
       ContentTruncatingNodeVisitor visitor = new ContentTruncatingNodeVisitor(
         length,
         ends,
@@ -171,8 +186,7 @@ private static class ContentTruncatingNodeVisitor implements NodeVisitor {
 
     @Override
     public void head(Node node, int depth) {
-      if (node instanceof TextNode) {
-        TextNode text = (TextNode) node;
+      if (node instanceof TextNode text) {
         String textContent = text.text();
 
         if (textLen >= maxTextLen) {
@@ -193,8 +207,7 @@ public void head(Node node, int depth) {
 
     @Override
     public void tail(Node node, int depth) {
-      if (node instanceof Element) {
-        Element el = (Element) node;
+      if (node instanceof Element el) {
         if (StringUtils.isBlank(el.text())) {
           el.addClass("__deleteme");
         }

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

@@ -1,12 +1,22 @@
 package com.hubspot.jinjava.lib.filter;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 import com.google.common.collect.ImmutableMap;
 import com.google.common.io.Resources;
 import com.hubspot.jinjava.BaseInterpretingTest;
+import com.hubspot.jinjava.interpret.Context;
+import com.hubspot.jinjava.interpret.DeferredValueException;
+import com.hubspot.jinjava.interpret.JinjavaInterpreter;
+import com.hubspot.jinjava.lib.tag.eager.DeferredToken;
+import com.hubspot.jinjava.tree.parse.ExpressionToken;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.util.Collections;
+import java.util.concurrent.atomic.AtomicInteger;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -54,6 +64,59 @@ public void itDoesntChopWordsWhenSpecified() {
       );
   }
 
+  @Test
+  public void itExecutesJinjavaInsideTag() {
+    assertThat(
+      filter.filter("{% for i in [1, 2, 3] %}<div>{{i}}</div>{% endfor %}", interpreter)
+    )
+      .isEqualTo("<div>\n 1\n</div>\n<div>\n 2\n</div>\n<div>\n 3\n</div>");
+  }
+
+  @Test
+  public void itExecutesJinjavaInsideTagAndTruncates() {
+    assertThat(
+      filter.filter(
+        "{% for i in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12] %}<div>{{i}}</div>{% endfor %}",
+        interpreter,
+        "10"
+      )
+    )
+      .isEqualTo(
+        "<div>\n 1\n</div>\n<div>\n 2\n</div>\n<div>\n 3\n</div>\n<div>\n 4\n</div>\n<div>\n 5\n</div>\n" +
+        "<div>\n 6\n</div>\n<div>\n 7\n</div>\n<div>\n 8\n</div>\n<div>\n 9\n</div>\n<div>\n ...\n</div>"
+      );
+  }
+
+  @Test
+  public void itIsolatesJinjavaScopeWhenExecutingCodeInsideTag() {
+    filter.filter("{% set test = 'hello' %}", interpreter);
+    assertThat(interpreter.getContext().get("test")).isNull();
+  }
+
+  @Test
+  public void itThrowsDeferredValueExceptionWhenDeferredTokensAreLeft() {
+    AtomicInteger counter = new AtomicInteger();
+    JinjavaInterpreter mockedInterpreter = mock(JinjavaInterpreter.class);
+    Context mockedContext = mock(Context.class);
+    when(mockedInterpreter.getContext()).thenReturn(mockedContext);
+    when(mockedContext.getDeferredTokens())
+      .thenAnswer(i ->
+        counter.getAndIncrement() == 0
+          ? Collections.emptySet()
+          : Collections.singleton(
+            DeferredToken
+              .builderFromImage(
+                "{{ deferred && other }}",
+                ExpressionToken.class,
+                interpreter
+              )
+              .build()
+          )
+      );
+    assertThatThrownBy(() -> filter.filter("{{ deferred && other }}", mockedInterpreter))
+      .isInstanceOf(DeferredValueException.class);
+  }
+
   @Test
   public void itTakesKwargs() {
     String result = (String) filter.filter(