Watcher: cleanup ensureWatchExists use (#31926)

Previously, the ensureWatchExists was overridable. This commit makes
it final so that it cannot be overridden, and cleans up some redundant
code in the process.

Author: hub-cap

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/watcher/execution/WatchExecutionContext.java

@@ -82,7 +82,7 @@ public Watch watch() {
         return watch;
     }
 
-    public void ensureWatchExists(CheckedSupplier<Watch, Exception> supplier) throws Exception {
+    public final void ensureWatchExists(CheckedSupplier<Watch, Exception> supplier) throws Exception {
         if (watch == null) {
             watch = supplier.get();
         }

x-pack/plugin/watcher/src/main/java/org/elasticsearch/xpack/watcher/execution/ManualExecutionContext.java

@@ -5,7 +5,6 @@
  */
 package org.elasticsearch.xpack.watcher.execution;
 
-import org.elasticsearch.common.CheckedSupplier;
 import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.xpack.core.watcher.actions.Action;
 import org.elasticsearch.xpack.core.watcher.actions.ActionWrapper;
@@ -29,18 +28,19 @@ public class ManualExecutionContext extends WatchExecutionContext {
     private final Map<String, ActionExecutionMode> actionModes;
     private final boolean recordExecution;
     private final boolean knownWatch;
-    private final Watch watch;
 
     ManualExecutionContext(Watch watch, boolean knownWatch, DateTime executionTime, ManualTriggerEvent triggerEvent,
                            TimeValue defaultThrottlePeriod, Input.Result inputResult, Condition.Result conditionResult,
-                           Map<String, ActionExecutionMode> actionModes, boolean recordExecution) {
+                           Map<String, ActionExecutionMode> actionModes, boolean recordExecution) throws Exception {
 
         super(watch.id(), executionTime, triggerEvent, defaultThrottlePeriod);
 
         this.actionModes = actionModes;
         this.recordExecution = recordExecution;
         this.knownWatch = knownWatch;
-        this.watch = watch;
+
+        // set the watch early to ensure calls to watch() below succeed.
+        super.ensureWatchExists(() -> watch);
 
         if (inputResult != null) {
             onInputResult(inputResult);
@@ -66,12 +66,6 @@ public class ManualExecutionContext extends WatchExecutionContext {
         }
     }
 
-    // a noop operation, as the watch is already loaded via ctor
-    @Override
-    public void ensureWatchExists(CheckedSupplier<Watch, Exception> supplier) throws Exception {
-        super.ensureWatchExists(() -> watch);
-    }
-
     @Override
     public boolean knownWatch() {
         return knownWatch;
@@ -107,11 +101,6 @@ public final boolean recordExecution() {
         return recordExecution;
     }
 
-    @Override
-    public Watch watch() {
-        return watch;
-    }
-
     public static Builder builder(Watch watch, boolean knownWatch, ManualTriggerEvent event, TimeValue defaultThrottlePeriod) {
         return new Builder(watch, knownWatch, event, defaultThrottlePeriod);
     }
@@ -173,7 +162,7 @@ public Builder withCondition(Condition.Result conditionResult) {
             return this;
         }
 
-        public ManualExecutionContext build() {
+        public ManualExecutionContext build() throws Exception {
             if (executionTime == null) {
                 executionTime = DateTime.now(DateTimeZone.UTC);
             }