runtime-v2: allow plugins to supply custom EL functions (#1225)

Author: ibodrov

runtime/v2/runner-test/src/test/java/com/walmartlabs/concord/runtime/v2/runner/MainTest.java

@@ -1746,6 +1746,20 @@ public void flowCallOutExpressionCompat() throws Exception {
         assertLog(runtime.allLogs(), ".*" + Pattern.quote("out as map with loop: [abc_0, abc_1]") + ".*");
     }
 
+    @Test
+    public void prefixedFunctionsInExpressions() throws Exception {
+        deploy("prefixedFunctions");
+
+        save(ProcessConfiguration.builder()
+                .putArguments("name", "world")
+                .build());
+
+        run();
+
+        assertLog(runtime.allLogs(), ".*Hi, world!.*");
+        assertLog(runtime.allLogs(), ".*Hello, world!.*");
+    }
+
     private void deploy(String name) throws URISyntaxException, IOException {
         runtime.deploy(name);
     }

runtime/v2/runner-test/src/test/java/com/walmartlabs/concord/runtime/v2/runner/functions/TestFunction.java

@@ -0,0 +1,19 @@
+package com.walmartlabs.concord.runtime.v2.runner.functions;
+
+import com.walmartlabs.concord.runtime.v2.sdk.ELFunction;
+
+import javax.inject.Named;
+
+@Named
+public class TestFunction {
+
+    @ELFunction("testGreet")
+    public static String regularGreet(String name) {
+        return "Hi, " + name + "!";
+    }
+
+    @ELFunction("testFunction:greet")
+    public static String prefixedGreet(String name) {
+        return "Hello, " + name + "!";
+    }
+}

runtime/v2/runner-test/src/test/resources/com/walmartlabs/concord/runtime/v2/runner/prefixedFunctions/concord.yml

@@ -0,0 +1,4 @@
+flows:
+  default:
+    - log: "${testGreet(name)}"
+    - log: "${testFunction:greet(name)}"

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/DefaultExpressionEvaluator.java

@@ -36,10 +36,11 @@ public class DefaultExpressionEvaluator implements ExpressionEvaluator {
 
     @Inject
     public DefaultExpressionEvaluator(TaskProviders taskProviders,
+                                      FunctionHolder functionHolder,
                                       List<CustomTaskMethodResolver> taskMethodResolvers,
                                       List<CustomBeanMethodResolver> beanMethodResolvers,
                                       SensitiveDataProcessor sensitiveDataProcessor) {
-        this.delegate = new LazyExpressionEvaluator(taskProviders, taskMethodResolvers, beanMethodResolvers, sensitiveDataProcessor);
+        this.delegate = new LazyExpressionEvaluator(taskProviders, functionHolder, taskMethodResolvers, beanMethodResolvers, sensitiveDataProcessor);
     }
 
     @Override

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/FunctionMapper.java renamed to runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/FunctionHolder.java

@@ -22,21 +22,23 @@
 
 import java.lang.reflect.Method;
 import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 
-public class FunctionMapper extends javax.el.FunctionMapper {
+public class FunctionHolder {
 
-    private final Map<String, Method> functions;
+    private final Map<String, Method> functions = new ConcurrentHashMap<>();
 
-    public FunctionMapper(Map<String, Method> functions) {
-        this.functions = functions;
+    public FunctionHolder register(String name, Method method) {
+        functions.put(name, method);
+        return this;
     }
 
-    @Override
-    public Method resolveFunction(String prefix, String localName) {
-        if (prefix == null || prefix.trim().isEmpty()) {
-            return functions.get(localName);
-        }
+    public Method resolve(String name) {
+        return functions.get(name);
+    }
 
-        return functions.get(prefix + ":" + localName);
+    public Set<String> names() {
+        return Set.copyOf(functions.keySet());
     }
 }

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/LazyExpressionEvaluator.java

@@ -22,9 +22,8 @@
 
 import com.walmartlabs.concord.common.ConfigurationUtils;
 import com.walmartlabs.concord.common.ExceptionUtils;
-import com.walmartlabs.concord.runtime.v2.runner.el.functions.*;
-import com.walmartlabs.concord.runtime.v2.runner.el.resolvers.MapELResolver;
 import com.walmartlabs.concord.runtime.v2.runner.el.resolvers.*;
+import com.walmartlabs.concord.runtime.v2.runner.el.resolvers.MapELResolver;
 import com.walmartlabs.concord.runtime.v2.runner.tasks.TaskProviders;
 import com.walmartlabs.concord.runtime.v2.runner.vm.WrappedException;
 import com.walmartlabs.concord.runtime.v2.sdk.*;
@@ -50,12 +49,13 @@ public class LazyExpressionEvaluator implements ExpressionEvaluator {
     private final SensitiveDataProcessor sensitiveDataProcessor;
 
     public LazyExpressionEvaluator(TaskProviders taskProviders,
+                                   FunctionHolder functionHolder,
                                    List<CustomTaskMethodResolver> taskMethodResolvers,
                                    List<CustomBeanMethodResolver> beanMethodResolvers,
                                    SensitiveDataProcessor sensitiveDataProcessor) {
         this.taskProviders = taskProviders;
         this.sensitiveDataProcessor = sensitiveDataProcessor;
-        this.functionMapper = createFunctionMapper();
+        this.functionMapper = new DelegatingFunctionMapper(functionHolder);
         this.taskMethodResolvers = taskMethodResolvers;
         this.beanMethodResolvers = beanMethodResolvers;
     }
@@ -203,22 +203,6 @@ private ELResolver createResolver(LazyEvalContext evalContext,
         return r;
     }
 
-    private static FunctionMapper createFunctionMapper() {
-        var functions = new HashMap<String, Method>();
-        functions.put("hasVariable", HasVariableFunction.getMethod());
-        functions.put("hasNonNullVariable", HasNonNullVariableFunction.getMethod());
-        functions.put("orDefault", OrDefaultFunction.getMethod());
-        functions.put("allVariables", AllVariablesFunction.getMethod());
-        functions.put("currentFlowName", CurrentFlowNameFunction.getMethod());
-        functions.put("evalAsMap", EvalAsMapFunction.getMethod());
-        functions.put("isDebug", IsDebugFunction.getMethod());
-        functions.put("throw", ThrowFunction.getMethod());
-        functions.put("hasFlow", HasFlowFunction.getMethod());
-        functions.put("uuid", UuidFunction.getMethod());
-        functions.put("isDryRun", IsDryRunFunction.getMethod());
-        return new FunctionMapper(functions);
-    }
-
     private static boolean hasExpression(String s) {
         return s.contains("${");
     }
@@ -272,4 +256,20 @@ private static Optional<String> propertyNameFromException(PropertyNotFoundExcept
 
         return Optional.empty();
     }
+
+    private static class DelegatingFunctionMapper extends FunctionMapper {
+        final FunctionHolder functionHolder;
+
+        DelegatingFunctionMapper(FunctionHolder functionHolder) {
+            this.functionHolder = functionHolder;
+        }
+
+        @Override
+        public Method resolveFunction(String prefix, String localName) {
+            if (prefix != null && !prefix.isBlank()) {
+                return functionHolder.resolve(prefix + ":" + localName);
+            }
+            return functionHolder.resolve(localName);
+        }
+    }
 }

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/functions/AllVariablesFunction.java

@@ -4,7 +4,7 @@
  * *****
  * Concord
  * -----
- * Copyright (C) 2017 - 2020 Walmart Inc.
+ * Copyright (C) 2017 - 2025 Walmart Inc.
  * -----
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,21 +20,14 @@
  * =====
  */
 
+import com.walmartlabs.concord.runtime.v2.sdk.ELFunction;
 import com.walmartlabs.concord.runtime.v2.runner.el.ThreadLocalEvalContext;
 
-import java.lang.reflect.Method;
 import java.util.Map;
 
 public final class AllVariablesFunction {
 
-    public static Method getMethod() {
-        try {
-            return AllVariablesFunction.class.getMethod("allVariables");
-        } catch (Exception e) {
-            throw new RuntimeException("Method not found");
-        }
-    }
-
+    @ELFunction
     public static Map<String, Object> allVariables() {
         return ThreadLocalEvalContext.get()
                 .variables()

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/functions/CurrentFlowNameFunction.java

@@ -4,7 +4,7 @@
  * *****
  * Concord
  * -----
- * Copyright (C) 2017 - 2020 Walmart Inc.
+ * Copyright (C) 2017 - 2025 Walmart Inc.
  * -----
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,21 +20,13 @@
  * =====
  */
 
+import com.walmartlabs.concord.runtime.v2.sdk.ELFunction;
 import com.walmartlabs.concord.runtime.v2.runner.el.ThreadLocalEvalContext;
 import com.walmartlabs.concord.runtime.v2.sdk.Context;
 
-import java.lang.reflect.Method;
-
 public final class CurrentFlowNameFunction {
 
-    public static Method getMethod() {
-        try {
-            return CurrentFlowNameFunction.class.getMethod("currentFlowName");
-        } catch (Exception e) {
-            throw new RuntimeException("Method not found");
-        }
-    }
-
+    @ELFunction
     public static String currentFlowName() {
         Context ctx = ThreadLocalEvalContext.get().context();
         if (ctx == null) {

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/functions/EvalAsMapFunction.java

@@ -4,7 +4,7 @@
  * *****
  * Concord
  * -----
- * Copyright (C) 2017 - 2020 Walmart Inc.
+ * Copyright (C) 2017 - 2025 Walmart Inc.
  * -----
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,28 +20,21 @@
  * =====
  */
 
-import com.walmartlabs.concord.runtime.v2.sdk.EvalContextFactory;
-import com.walmartlabs.concord.runtime.v2.sdk.ExpressionEvaluator;
+import com.walmartlabs.concord.runtime.v2.sdk.ELFunction;
 import com.walmartlabs.concord.runtime.v2.runner.el.ThreadLocalEvalContext;
 import com.walmartlabs.concord.runtime.v2.sdk.Context;
+import com.walmartlabs.concord.runtime.v2.sdk.EvalContextFactory;
+import com.walmartlabs.concord.runtime.v2.sdk.ExpressionEvaluator;
 import com.walmartlabs.concord.svm.Runtime;
 
-import java.lang.reflect.Method;
 import java.util.HashMap;
 import java.util.Map;
 
 import static com.walmartlabs.concord.common.ConfigurationUtils.deepMerge;
 
 public final class EvalAsMapFunction {
 
-    public static Method getMethod() {
-        try {
-            return EvalAsMapFunction.class.getMethod("evalAsMap", Object.class);
-        } catch (Exception e) {
-            throw new RuntimeException("Method not found");
-        }
-    }
-
+    @ELFunction
     @SuppressWarnings("unchecked")
     public static Map<String, Object> evalAsMap(Object value) {
         Context ctx = ThreadLocalEvalContext.get().context();

runtime/v2/runner/src/main/java/com/walmartlabs/concord/runtime/v2/runner/el/functions/HasFlowFunction.java

@@ -22,21 +22,13 @@
 
 import com.walmartlabs.concord.runtime.v2.model.ProcessDefinition;
 import com.walmartlabs.concord.runtime.v2.model.Profile;
+import com.walmartlabs.concord.runtime.v2.sdk.ELFunction;
 import com.walmartlabs.concord.runtime.v2.runner.el.ThreadLocalEvalContext;
 import com.walmartlabs.concord.runtime.v2.sdk.Context;
 
-import java.lang.reflect.Method;
-
 public final class HasFlowFunction {
 
-    public static Method getMethod() {
-        try {
-            return HasFlowFunction.class.getMethod("hasFlow", String.class);
-        } catch (Exception e) {
-            throw new RuntimeException("Method not found");
-        }
-    }
-
+    @ELFunction
     public static boolean hasFlow(String name) {
         if (name == null || name.trim().isEmpty()) {
             return false;