allow pre-use verification of command availability

engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/session/NBAutoScriptResolver.java

@@ -53,5 +53,15 @@ public class NBAutoScriptResolver implements NBInvokableResolver {
         }
     }
 
+    @Override
+    public boolean verify(Cmd cmd) {
+        return NBIO.local()
+                .searchPrefixes("scripts/auto")
+                .pathname(cmd.getArgValue("_impl"))
+                .extensionSet("js")
+                .first()
+            .isPresent();
+    }
+
 
 }

engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/session/NBCoreInvokableResolver.java

@@ -45,6 +45,16 @@ public class NBCoreInvokableResolver implements NBInvokableResolver {
         return null;
     }
 
+    @Override
+    public boolean verify(Cmd cmd) {
+        for (NBInvokableResolver resolver : getResolvers().values()) {
+            if (resolver.verify(cmd)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     private SequencedMap<String, NBInvokableResolver> getResolvers() {
         if (this.resolvers == null || this.resolvers.isEmpty()) {
             SequencedMap<String,NBInvokableResolver> resolverMap = new LinkedHashMap<>();

engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/session/NBInvokableResolver.java

@@ -21,6 +21,8 @@ import io.nosqlbench.engine.core.lifecycle.scenario.container.NBBufferedContaine
 import io.nosqlbench.engine.core.lifecycle.scenario.execution.NBInvokableCommand;
 
 public interface NBInvokableResolver {
-    NBInvokableCommand resolve(Cmd cmd, NBBufferedContainer parent, String phaseName);
+    NBInvokableCommand resolve(Cmd cmd, NBBufferedContainer parent, String stepname);
+
+    boolean verify(Cmd cmd);
 
 }

engine-core/src/main/java/io/nosqlbench/engine/core/lifecycle/session/NBScriptCommandResolver.java

@@ -37,5 +37,8 @@ public class NBScriptCommandResolver implements NBInvokableResolver {
         };
     }
 
-
+    @Override
+    public boolean verify(Cmd cmd) {
+        return true;
+    }
 }