Improved UI error messages when the parameter must be a constant

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

@@ -832,6 +832,18 @@ public void visitInvokeCallMember(InvokeCallMemberNode irInvokeCallMemberNode, C
         }
     }
 
+    private String convertIntToOrdinal(int i) {
+        String[] suffixes = new String[] { "th", "st", "nd", "rd", "th", "th", "th", "th", "th", "th" };
+        switch (i % 100) {
+            case 11:
+            case 12:
+            case 13:
+                return i + "th";
+            default:
+                return i + suffixes[i % 10];
+        }
+    }
+
     private void replaceCallWithConstant(
         InvokeCallMemberNode irInvokeCallMemberNode,
         Consumer<ExpressionNode> scope,
@@ -843,11 +855,11 @@ private void replaceCallWithConstant(
             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"
+                            "The [" + javaMethod.getName() + "] method needs constant arguments to work properly. " +
+                                "Please provide a constant to the [" + convertIntToOrdinal(i + 1) + "] argument"
                         )
                     );
             }

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

@@ -211,7 +211,8 @@ public void testClassMethodCompileTimeOnlyVariableParams() {
             IllegalArgumentException.class,
             () -> scriptEngine.compile(null, "def a = 2; classMul(2, a)", 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("The [classMul] method needs constant arguments to work properly. " +
+            "Please provide a constant to the second argument"));
     }
 
     public void testClassMethodCompileTimeOnlyThrows() {
@@ -240,7 +241,8 @@ 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("The [instanceMul] method needs constant arguments to work properly. " +
+            "Please provide a constant to the first argument"));
     }
 
     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: /The \[grok\] method needs constant arguments to work properly. Please provide a constant to the first argument/
       search:
         index: http_logs
         body: