From 3d243f622a0d8bd557f1541f5edb243114a70983 Mon Sep 17 00:00:00 2001
From: Aayush Tiwari <aayushtiwari1001@gmail.com>
Date: Sat, 11 Jul 2026 20:15:26 +0530
Subject: [PATCH] Add yaml.is_valid builtin

Signed-off-by: Aayush Tiwari <aayushtiwari1001@gmail.com>
---
 .../opa-builtins-json/build.gradle.kts        |  7 ++++
 .../opa/ast/builtin/impls/JsonBuiltins.java   | 23 ++++++++++++-
 .../ast/builtin/impls/JsonBuiltinsTest.java   | 33 +++++++++++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 opa-builtins/opa-builtins-json/src/test/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltinsTest.java

diff --git a/opa-builtins/opa-builtins-json/build.gradle.kts b/opa-builtins/opa-builtins-json/build.gradle.kts
index e23c02f6..1a2890e0 100644
--- a/opa-builtins/opa-builtins-json/build.gradle.kts
+++ b/opa-builtins/opa-builtins-json/build.gradle.kts
@@ -18,6 +18,9 @@ dependencies {
     // RegoValueModule (auto-registered via Jackson SPI) provides (de)serializers for the AST
     // types so they don't need to carry annotations.
     runtimeOnly(project(":opa-jackson"))
+
+    testImplementation("org.junit.jupiter:junit-jupiter:6.1.1")
+    testRuntimeOnly("org.junit.platform:junit-platform-launcher:6.1.1")
 }
 
 java {
@@ -25,3 +28,7 @@ java {
         languageVersion = JavaLanguageVersion.of(17)
     }
 }
+
+tasks.test {
+    useJUnitPlatform()
+}
diff --git a/opa-builtins/opa-builtins-json/src/main/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltins.java b/opa-builtins/opa-builtins-json/src/main/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltins.java
index 2cc6a725..7b2da5c8 100644
--- a/opa-builtins/opa-builtins-json/src/main/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltins.java
+++ b/opa-builtins/opa-builtins-json/src/main/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltins.java
@@ -123,6 +123,7 @@ public Map<String, BiFunction<EvaluationContext, RegoValue[], RegoValue>> builti
     result.put("json.remove", instance::remove);
     result.put("json.unmarshal", instance::unmarshal);
     result.put("json.verify_schema", instance::verify_schema);
+    result.put("yaml.is_valid", instance::yamlIsValid);
     result.put("yaml.marshal", instance::yamlMarshal);
     result.put("yaml.unmarshal", instance::yamlUnmarshal);
     return result;
@@ -706,6 +707,26 @@ public RegoString yamlMarshal(EvaluationContext ctx, RegoValue[] args) {
     }
   }
 
+  @OpaBuiltin(
+          name = "yaml.is_valid",
+          description = "Verifies the input string is a valid YAML document.",
+          categories = {"encoding"},
+          args = {@OpaType(type = "string", name = "x", description = "a YAML string")},
+          result =
+          @OpaType(
+                  name = "result",
+                  description = "`true` if `x` is valid YAML, `false` otherwise"))
+  public RegoBoolean yamlIsValid(EvaluationContext ctx, RegoValue[] args) {
+    String yamlInput = getArg(args, 0, RegoString.class).getValue();
+
+    try {
+      YAML_MAPPER.readTree(yamlInput);
+      return RegoBoolean.TRUE;
+    } catch (JsonProcessingException e) {
+      return RegoBoolean.FALSE;
+    }
+  }
+
   @OpaBuiltin(
           name = "yaml.unmarshal",
           description = "Deserializes the input YAML string.",
@@ -1071,4 +1092,4 @@ private JsonNode removeNodes(JsonNode node, Set<String> paths) {
 
     return result;
   }
-}
\ No newline at end of file
+}
diff --git a/opa-builtins/opa-builtins-json/src/test/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltinsTest.java b/opa-builtins/opa-builtins-json/src/test/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltinsTest.java
new file mode 100644
index 00000000..1bdc7cd9
--- /dev/null
+++ b/opa-builtins/opa-builtins-json/src/test/java/io/github/open_policy_agent/opa/ast/builtin/impls/JsonBuiltinsTest.java
@@ -0,0 +1,33 @@
+package io.github.open_policy_agent.opa.ast.builtin.impls;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import io.github.open_policy_agent.opa.ast.types.RegoBoolean;
+import io.github.open_policy_agent.opa.ast.types.RegoString;
+import io.github.open_policy_agent.opa.ast.types.RegoValue;
+import org.junit.jupiter.api.Test;
+
+class JsonBuiltinsTest {
+
+  private final JsonBuiltins builtins = new JsonBuiltins();
+
+  @Test
+  void registersYamlIsValidBuiltin() {
+    assertTrue(builtins.builtins().containsKey("yaml.is_valid"));
+  }
+
+  @Test
+  void yamlIsValidReturnsTrueForValidYaml() {
+    RegoValue[] args = {new RegoString("name: opa\nvalues:\n  - sdk\n  - java\n")};
+
+    assertEquals(RegoBoolean.TRUE, builtins.yamlIsValid(null, args));
+  }
+
+  @Test
+  void yamlIsValidReturnsFalseForInvalidYaml() {
+    RegoValue[] args = {new RegoString("name: [unterminated")};
+
+    assertEquals(RegoBoolean.FALSE, builtins.yamlIsValid(null, args));
+  }
+}