feat(pipeline/expressions): support yaml parsing (#2946)

This patch adds two helper functions `readYaml` and
`yamlFromUrl` to transfrom yaml strings (either
embedded or from retrieved from an URL) to their
object representation.

DNMY: missing tests

orca-core/orca-core.gradle

@@ -49,6 +49,7 @@ dependencies {
   implementation("org.apache.commons:commons-lang3")
   implementation("javax.servlet:javax.servlet-api:4.0.1")
   implementation("com.jayway.jsonpath:json-path:2.2.0")
+  implementation("org.yaml:snakeyaml")
 
   compileOnly("org.projectlombok:lombok")
   annotationProcessor("org.projectlombok:lombok")

orca-core/src/main/java/com/netflix/spinnaker/orca/pipeline/expressions/ExpressionsSupport.java

@@ -39,6 +39,7 @@
 import org.springframework.expression.ParserContext;
 import org.springframework.expression.common.TemplateParserContext;
 import org.springframework.expression.spel.support.StandardEvaluationContext;
+import org.yaml.snakeyaml.Yaml;
 
 /**
  * Provides utility support for SPEL integration Supports registering SPEL functions, ACLs to
@@ -60,6 +61,7 @@ public class ExpressionsSupport {
     registeredHelperFunctions.put("alphanumerical", Collections.singletonList(String.class));
     registeredHelperFunctions.put("toJson", Collections.singletonList(Object.class));
     registeredHelperFunctions.put("readJson", Collections.singletonList(String.class));
+    registeredHelperFunctions.put("readYaml", Collections.singletonList(String.class));
     registeredHelperFunctions.put("toInt", Collections.singletonList(String.class));
     registeredHelperFunctions.put("toFloat", Collections.singletonList(String.class));
     registeredHelperFunctions.put("toBoolean", Collections.singletonList(String.class));
@@ -99,6 +101,7 @@ public static StandardEvaluationContext newEvaluationContext(
         // lazily function registering
         registerFunction(evaluationContext, "fromUrl", String.class);
         registerFunction(evaluationContext, "jsonFromUrl", String.class);
+        registerFunction(evaluationContext, "yamlFromUrl", String.class);
         registerFunction(evaluationContext, "propertiesFromUrl", String.class);
         registerFunction(evaluationContext, "stage", Object.class, String.class);
         registerFunction(evaluationContext, "stageExists", Object.class, String.class);
@@ -254,6 +257,20 @@ static Object readJson(String text) {
     }
   }
 
+  /**
+   * Attempts to read yaml from a text String. Will throw a parsing exception on bad yaml
+   *
+   * @param text text to read as yaml
+   * @return the object representation of the yaml text
+   */
+  static Object readYaml(String text) {
+    try {
+      return new Yaml().load(text);
+    } catch (Exception e) {
+      throw new SpelHelperFunctionException(format("#readYaml(%s) failed", text), e);
+    }
+  }
+
   /**
    * Reads a json text
    *
@@ -264,6 +281,16 @@ static Object jsonFromUrl(String url) {
     return readJson(fromUrl(url));
   }
 
+  /**
+   * Reads a yaml text
+   *
+   * @param url url to get the json text
+   * @return an object representing the yaml object
+   */
+  static Object yamlFromUrl(String url) {
+    return readYaml(fromUrl(url));
+  }
+
   /**
    * Reads a properties file stored at a url
    *