From 468d50a467710c6a0910c49dc064d1d16561518f Mon Sep 17 00:00:00 2001
From: Jaehong Park <105151063+PHJ2000@users.noreply.github.com>
Date: Thu, 22 Oct 2026 19:53:41 +0900
Subject: [PATCH] Allow the default filter value to be omitted

Signed-off-by: Jaehong Park <105151063+PHJ2000@users.noreply.github.com>
---
 .../jinjava/lib/filter/DefaultFilter.java     | 14 ++------
 .../jinjava/lib/filter/DefaultFilterTest.java | 34 +++++++++++++++++++
 2 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/src/main/java/com/hubspot/jinjava/lib/filter/DefaultFilter.java b/src/main/java/com/hubspot/jinjava/lib/filter/DefaultFilter.java
index d93170d6a..2eb697ce9 100644
--- a/src/main/java/com/hubspot/jinjava/lib/filter/DefaultFilter.java
+++ b/src/main/java/com/hubspot/jinjava/lib/filter/DefaultFilter.java
@@ -19,7 +19,6 @@
 import com.hubspot.jinjava.doc.annotations.JinjavaParam;
 import com.hubspot.jinjava.doc.annotations.JinjavaSnippet;
 import com.hubspot.jinjava.interpret.JinjavaInterpreter;
-import com.hubspot.jinjava.interpret.TemplateSyntaxException;
 import com.hubspot.jinjava.objects.PyWrapper;
 import com.hubspot.jinjava.util.ObjectTruthValue;
 import java.util.Map;
@@ -36,8 +35,7 @@
     @JinjavaParam(
       value = DefaultFilter.DEFAULT_VALUE_PARAM,
       type = "object",
-      desc = "Value to print when variable is not defined",
-      required = true
+      desc = "Value to print when variable is not defined; defaults to an empty string"
     ),
     @JinjavaParam(
       value = DefaultFilter.TRUTHY_PARAM,
@@ -68,16 +66,8 @@ public Object filter(
     JinjavaInterpreter interpreter,
     Map<String, Object> parsedArgs
   ) {
-    if (parsedArgs.size() < 1) {
-      throw new TemplateSyntaxException(
-        interpreter,
-        getName(),
-        "requires either 1 (default value to use) or 2 (default value to use, default with variables that evaluate to false) arguments"
-      );
-    }
-
     boolean truthy = Boolean.TRUE.equals(parsedArgs.get(TRUTHY_PARAM));
-    Object defaultValue = parsedArgs.get(DEFAULT_VALUE_PARAM);
+    Object defaultValue = parsedArgs.getOrDefault(DEFAULT_VALUE_PARAM, "");
 
     if (truthy) {
       if (ObjectTruthValue.evaluate(object)) {
diff --git a/src/test/java/com/hubspot/jinjava/lib/filter/DefaultFilterTest.java b/src/test/java/com/hubspot/jinjava/lib/filter/DefaultFilterTest.java
index 0faa5d4bc..5d1e7a4f6 100644
--- a/src/test/java/com/hubspot/jinjava/lib/filter/DefaultFilterTest.java
+++ b/src/test/java/com/hubspot/jinjava/lib/filter/DefaultFilterTest.java
@@ -18,6 +18,40 @@ public void setup() {
     jinjava.getGlobalContext().registerClasses(DefaultFilter.class);
   }
 
+  @Test
+  public void itKeepsDefinedValuesWithoutADefaultArgument() {
+    assertThat(jinjava.render("{{ 'a' | default }}", new HashMap<>())).isEqualTo("a");
+    assertThat(jinjava.render("{{ 0 | default() }}", new HashMap<>())).isEqualTo("0");
+  }
+
+  @Test
+  public void itDefaultsUndefinedValuesToAnEmptyString() {
+    assertThat(
+      jinjava.render(
+        "{% set value = missing | default %}{{ type(value) }}:{{ value | length }}",
+        new HashMap<>()
+      )
+    )
+      .isEqualTo("str:0");
+  }
+
+  @Test
+  public void itDefaultsFalsyValuesWithoutAnExplicitDefault() {
+    assertThat(
+      jinjava.render(
+        "{% set value = false | default(truthy=True) %}{{ type(value) }}:{{ value | length }}",
+        new HashMap<>()
+      )
+    )
+      .isEqualTo("str:0");
+  }
+
+  @Test
+  public void itAllowsOmittedArgumentsForTheAlias() {
+    assertThat(jinjava.render("{{ 'a' | d }}:{{ missing | d }}", new HashMap<>()))
+      .isEqualTo("a:");
+  }
+
   @Test
   public void itSetsDefaultStringValues() {
     assertThat(