Introduces a limited length render filter and HTML tag close filter

src/main/java/com/hubspot/jinjava/interpret/JinjavaInterpreter.java

@@ -259,7 +259,11 @@ public String renderFlat(String template) {
    * @return rendered result
    */
   public String render(String template) {
-    return render(parse(template), true);
+    return render(template, config.getMaxOutputSize());
+  }
+
+  public String render(String template, long renderLimit) {
+    return render(parse(template), true, renderLimit);
   }
 
   /**
@@ -270,7 +274,19 @@ public String render(String template) {
    * @return rendered result
    */
   public String render(Node root) {
-    return render(root, true);
+    return render(root, true, config.getMaxOutputSize());
+  }
+
+  /**
+   * Render the given root node with an option to process extend parents.
+   * Equivalent to render(root, processExtendRoots).
+   * @param root
+   *          node to render
+   * @param processExtendRoots
+   * @return
+   */
+  public String render(Node root, boolean processExtendRoots) {
+    return render(root, processExtendRoots, config.getMaxOutputSize());
   }
 
   /**
@@ -280,11 +296,12 @@ public String render(Node root) {
    *          node to render
    * @param processExtendRoots
    *          if true, also render all extend parents
+   * @param renderLimit
+   *          the number of characters the result may contain
    * @return rendered result
    */
-  public String render(Node root, boolean processExtendRoots) {
-    OutputList output = new OutputList(config.getMaxOutputSize());
-
+  private String render(Node root, boolean processExtendRoots, long renderLimit) {
+    OutputList output = new OutputList(clampOutputSizeSafely(renderLimit));
     for (Node node : root.getChildren()) {
       lineNumber = node.getLineNumber();
       position = node.getStartPosition();
@@ -340,8 +357,8 @@ public String render(Node root, boolean processExtendRoots) {
         return output.getValue();
       }
     }
-    StringBuilder ignoredOutput = new StringBuilder();
 
+    StringBuilder ignoredOutput = new StringBuilder();
     // render all extend parents, keeping the last as the root output
     if (processExtendRoots) {
       Set<String> extendPaths = new HashSet<>();
@@ -406,6 +423,7 @@ public String render(Node root, boolean processExtendRoots) {
     }
 
     resolveBlockStubs(output);
+
     if (ignoredOutput.length() > 0) {
       return (
         EagerReconstructionUtils.labelWithNotes(
@@ -421,7 +439,6 @@ public String render(Node root, boolean processExtendRoots) {
         output.getValue()
       );
     }
-
     return output.getValue();
   }
 
@@ -907,6 +924,20 @@ private String getWrappedErrorMessage(
     }
   }
 
+  private long clampOutputSizeSafely(long providedLimit) {
+    long configMaxOutput = config.getMaxOutputSize();
+
+    if (configMaxOutput == 0) {
+      return providedLimit;
+    }
+
+    if (providedLimit <= 0) {
+      return configMaxOutput;
+    }
+
+    return Math.min(providedLimit, configMaxOutput);
+  }
+
   @Override
   @SuppressWarnings("unchecked")
   public <T extends Appendable & CharSequence> T appendPyishString(T appendable)

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

@@ -0,0 +1,26 @@
+package com.hubspot.jinjava.lib.filter;
+
+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.JinjavaInterpreter;
+import java.util.Objects;
+import org.jsoup.Jsoup;
+
+@JinjavaDoc(
+  value = "Closes open HTML tags in a string",
+  input = @JinjavaParam(value = "s", desc = "String to close", required = true),
+  snippets = { @JinjavaSnippet(code = "{{ \"<p> Hello, world\"|closehtml }}") }
+)
+public class CloseHtmlFilter implements Filter {
+
+  @Override
+  public String getName() {
+    return "closehtml";
+  }
+
+  @Override
+  public Object filter(Object var, JinjavaInterpreter interpreter, String... args) {
+    return Jsoup.parseBodyFragment(Objects.toString(var)).body().html();
+  }
+}

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

@@ -1,10 +1,12 @@
 package com.hubspot.jinjava.lib.filter;
 
+import com.hubspot.jinjava.JinjavaConfig;
 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.JinjavaInterpreter;
 import java.util.Objects;
+import org.apache.commons.lang3.math.NumberUtils;
 
 @JinjavaDoc(
   value = "Renders a template string early to be used by other filters and functions",
@@ -24,6 +26,16 @@ public String getName() {
 
   @Override
   public Object filter(Object var, JinjavaInterpreter interpreter, String... args) {
+    if (args.length > 0) {
+      String firstArg = args[0];
+      return interpreter.render(
+        Objects.toString(var),
+        NumberUtils.toLong(
+          firstArg,
+          JinjavaConfig.newBuilder().build().getMaxOutputSize()
+        )
+      );
+    }
     return interpreter.render(Objects.toString(var));
   }
 }

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

@@ -0,0 +1,35 @@
+package com.hubspot.jinjava.lib.filter;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.hubspot.jinjava.BaseInterpretingTest;
+import org.junit.Before;
+import org.junit.Test;
+
+public class CloseHtmlFilterTest extends BaseInterpretingTest {
+  CloseHtmlFilter f;
+
+  @Before
+  public void setup() {
+    f = new CloseHtmlFilter();
+  }
+
+  @Test
+  public void itClosesTags() {
+    String openTags = "<p>Hello, world!";
+    assertThat(f.filter(openTags, interpreter)).isEqualTo("<p>Hello, world!</p>");
+  }
+
+  @Test
+  public void itIgnoresClosedTags() {
+    String openTags = "<p>Hello, world!</p>";
+    assertThat(f.filter(openTags, interpreter)).isEqualTo("<p>Hello, world!</p>");
+  }
+
+  @Test
+  public void itClosesMultipleTags() {
+    String openTags = "<h1><p>Hello, world!";
+    assertThat(f.filter(openTags, interpreter))
+      .isEqualTo("<h1><p>Hello, world!</p></h1>");
+  }
+}

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

@@ -20,4 +20,42 @@ public void itRendersObject() {
 
     assertThat(filter.filter(stringToRender, interpreter)).isEqualTo("world");
   }
+
+  @Test
+  public void itRendersObjectWithinLimit() {
+    String stringToRender = "{% if null %}Hello{% else %}world{% endif %}";
+
+    assertThat(filter.filter(stringToRender, interpreter, "5")).isEqualTo("world");
+  }
+
+  @Test
+  public void itDoesNotRenderObjectOverLimit() {
+    String stringToRender = "{% if null %}Hello{% else %}world{% endif %}";
+
+    assertThat(filter.filter(stringToRender, interpreter, "4")).isEqualTo("");
+  }
+
+  @Test
+  public void itRendersPartialObjectOverLimit() {
+    String stringToRender = "Hello{% if null %}Hello{% else %}world{% endif %}";
+
+    assertThat(filter.filter(stringToRender, interpreter, "7")).isEqualTo("Hello");
+  }
+
+  @Test
+  public void itCountsHtmlTags() {
+    String stringToRender = "<p>Hello</p>{% if null %}Hello{% else %}world{% endif %}";
+
+    assertThat(filter.filter(stringToRender, interpreter, "15"))
+      .isEqualTo("<p>Hello</p>");
+  }
+
+  @Test
+  public void itDoesNotAlwaysCompleteHtmlTags() {
+    String stringToRender =
+      "<p> Hello, {% if null %}world{% else %}world!{% endif %} </p>";
+
+    assertThat(filter.filter(stringToRender, interpreter, "17"))
+      .isEqualTo("<p> Hello, world!");
+  }
 }