Improve error message in painless when parameter must be a constant but isn't

modules/lang-painless/src/main/java/org/elasticsearch/painless/phase/DefaultConstantFoldingOptimizationPhase.java

@@ -8,6 +8,7 @@
 
 package org.elasticsearch.painless.phase;
 
+import org.elasticsearch.core.Tuple;
 import org.elasticsearch.painless.AnalyzerCaster;
 import org.elasticsearch.painless.Operation;
 import org.elasticsearch.painless.ir.BinaryImplNode;
@@ -66,10 +67,15 @@
 import org.elasticsearch.painless.symbol.IRDecorations.IRDInstanceBinding;
 import org.elasticsearch.painless.symbol.IRDecorations.IRDMethod;
 import org.elasticsearch.painless.symbol.IRDecorations.IRDOperation;
+import org.elasticsearch.painless.symbol.IRDecorations.IRDName;
 
 import java.lang.reflect.InvocationTargetException;
 import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Locale;
 import java.util.function.Consumer;
+import java.util.stream.Collectors;
 
 /**
  * This optimization pass will perform the specified operation on two leafs nodes if they are both
@@ -1103,19 +1109,33 @@ private void replaceCallWithConstant(
         Object receiver
     ) {
         Object[] args = new Object[irInvokeCallMemberNode.getArgumentNodes().size()];
+
+        List<Tuple<Integer,String>> argumentsShouldBeConstants  = new ArrayList<>();
         for (int i = 0; i < irInvokeCallMemberNode.getArgumentNodes().size(); i++) {
             ExpressionNode argNode = irInvokeCallMemberNode.getArgumentNodes().get(i);
             IRDConstant constantDecoration = argNode.getDecoration(IRDConstant.class);
             if (constantDecoration == null) {
-                // TODO find a better string to output
-                throw irInvokeCallMemberNode.getLocation()
-                    .createError(
-                        new IllegalArgumentException(
-                            "all arguments to [" + javaMethod.getName() + "] must be constant but the [" + (i + 1) + "] argument isn't"
-                        )
-                    );
+                // offering the symbol name in error message (CastNode was evolved from ESymbol)
+                String argumentName = argNode instanceof CastNode
+                    ? ((CastNode) argNode).getChildNode().getDecoration(IRDName.class).getValue()
+                    : "";
+                argumentsShouldBeConstants.add(Tuple.tuple(i, argumentName));
+            } else {
+                args[i] = constantDecoration.getValue();
             }
-            args[i] = constantDecoration.getValue();
+        }
+        if (argumentsShouldBeConstants.size() > 0 ){
+            throw irInvokeCallMemberNode
+                .getLocation()
+                .createError(new IllegalArgumentException(String.format(
+                    Locale.ROOT,
+                    "All arguments of the [%s] method must be constants, but the following arguments are not: %s",
+                    javaMethod.getName(),
+                    argumentsShouldBeConstants
+                     .stream()
+                     .map(pair -> "argument [" + (pair.v1()+1) +"]"+ (pair.v2().isEmpty() ? "" : " named [" + pair.v2() + "]"))
+                     .collect(Collectors.joining(", "))
+                )));
         }
         Object result;
         try {

modules/lang-painless/src/test/java/org/elasticsearch/painless/BindingsTests.java

@@ -238,9 +238,10 @@ public void testClassMethodCompileTimeOnly() {
     public void testClassMethodCompileTimeOnlyVariableParams() {
         Exception e = expectScriptThrows(
             IllegalArgumentException.class,
-            () -> scriptEngine.compile(null, "def a = 2; classMul(2, a)", BindingsTestScript.CONTEXT, Collections.emptyMap())
+            () -> scriptEngine.compile(null, "def a = 2; def b = 3; classMul(a, b)", BindingsTestScript.CONTEXT, Collections.emptyMap())
         );
-        assertThat(e.getMessage(), equalTo("all arguments to [classMul] must be constant but the [2] argument isn't"));
+        assertThat(e.getMessage(), equalTo("All arguments of the [classMul] method must be constants," +
+            " but the following arguments are not: argument [1] named [a], argument [2] named [b]"));
     }
 
     public void testClassMethodCompileTimeOnlyThrows() {
@@ -269,7 +270,8 @@ public void testInstanceMethodCompileTimeOnlyVariableParams() {
             IllegalArgumentException.class,
             () -> scriptEngine.compile(null, "def a = 2; instanceMul(a, 2)", BindingsTestScript.CONTEXT, Collections.emptyMap())
         );
-        assertThat(e.getMessage(), equalTo("all arguments to [instanceMul] must be constant but the [1] argument isn't"));
+        assertThat(e.getMessage(), equalTo("All arguments of the [instanceMul] method must be constants," +
+            " but the following arguments are not: argument [1] named [a]"));
     }
 
     public void testCompileTimeOnlyParameterFoldedToConstant() {

modules/runtime-fields-common/src/yamlRestTest/resources/rest-api-spec/test/runtime_fields/250_grok.yml

@@ -80,7 +80,7 @@ fetch:
 ---
 mutable pattern:
   - do:
-      catch: /all arguments to \[grok\] must be constant but the \[1\] argument isn't/
+      catch: '/All arguments of the \[grok\] method must be constants, but the following arguments are not\: argument \[1\]/'
       search:
         index: http_logs
         body:

x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/runtime_fields/250_grok.yml

@@ -80,7 +80,7 @@ fetch:
 ---
 mutable pattern:
   - do:
-      catch: /all arguments to \[grok\] must be constant but the \[1\] argument isn't/
+      catch: '/All arguments of the \[grok\] method must be constants, but the following arguments are not\: argument \[1\]/'
       search:
         index: http_logs
         body: