From d8a4be9fce601f43d5befdab6916e48b44c234c5 Mon Sep 17 00:00:00 2001
From: Benjamin Trent <4357155+benwtrent@users.noreply.github.com>
Date: Tue, 18 May 2021 09:22:38 -0400
Subject: [PATCH] [ML] fix empty body on post issue for datafeed _preview

---
 .../core/ml/action/PreviewDatafeedAction.java | 10 ++++++++--
 .../datafeeds/RestPreviewDatafeedAction.java  |  5 ++++-
 .../test/ml/preview_datafeed.yml              | 19 +++++++++++++++++++
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/PreviewDatafeedAction.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/PreviewDatafeedAction.java
index afeaa2b33e486..c4e639cc57413 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/PreviewDatafeedAction.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/PreviewDatafeedAction.java
@@ -10,6 +10,7 @@
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionType;
+import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.ParseField;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
@@ -53,8 +54,13 @@ public static class Request extends ActionRequest implements ToXContentObject {
             PARSER.declareObject(Builder::setJobBuilder, Job.STRICT_PARSER, JOB_CONFIG);
         }
 
-        public static Request fromXContent(XContentParser parser) {
-            return PARSER.apply(parser, null).build();
+        public static Request fromXContent(XContentParser parser, @Nullable String datafeedId) {
+            Builder builder = PARSER.apply(parser, null);
+            // We don't need to check for "inconsistent ids" as we don't parse an ID from the body
+            if (datafeedId != null) {
+                builder.setDatafeedId(datafeedId);
+            }
+            return builder.build();
         }
 
         private final String datafeedId;
diff --git a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/rest/datafeeds/RestPreviewDatafeedAction.java b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/rest/datafeeds/RestPreviewDatafeedAction.java
index a7c264d513d30..537775850e044 100644
--- a/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/rest/datafeeds/RestPreviewDatafeedAction.java
+++ b/x-pack/plugin/ml/src/main/java/org/elasticsearch/xpack/ml/rest/datafeeds/RestPreviewDatafeedAction.java
@@ -40,7 +40,10 @@ public String getName() {
     @Override
     protected RestChannelConsumer prepareRequest(RestRequest restRequest, NodeClient client) throws IOException {
         PreviewDatafeedAction.Request request = restRequest.hasContentOrSourceParam() ?
-            PreviewDatafeedAction.Request.fromXContent(restRequest.contentOrSourceParamParser()) :
+            PreviewDatafeedAction.Request.fromXContent(
+                restRequest.contentOrSourceParamParser(),
+                restRequest.param(DatafeedConfig.ID.getPreferredName(), null)
+            ) :
             new PreviewDatafeedAction.Request(restRequest.param(DatafeedConfig.ID.getPreferredName()));
         return channel -> client.execute(PreviewDatafeedAction.INSTANCE, request, new RestToXContentListener<>(channel));
     }
diff --git a/x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/ml/preview_datafeed.yml b/x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/ml/preview_datafeed.yml
index 77a9fc71379e5..929182e6dad7e 100644
--- a/x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/ml/preview_datafeed.yml
+++ b/x-pack/plugin/src/yamlRestTest/resources/rest-api-spec/test/ml/preview_datafeed.yml
@@ -109,6 +109,25 @@ setup:
   - match: { 3.airline: foo }
   - match: { 3.responsetime: 42.0 }
 
+  - do:
+      ml.preview_datafeed:
+        datafeed_id: preview-datafeed-feed
+        body: >
+          {}
+  - length: { $body: 4 }
+  - match: { 0.time: 1487376000000 }
+  - match: { 0.airline: foo }
+  - match: { 0.responsetime: 1.0 }
+  - match: { 1.time: 1487377800000 }
+  - match: { 1.airline: foo }
+  - match: { 1.responsetime: 1.0 }
+  - match: { 2.time: 1487379600000 }
+  - match: { 2.airline: bar }
+  - match: { 2.responsetime: 42.0 }
+  - match: { 3.time: 1487379660000 }
+  - match: { 3.airline: foo }
+  - match: { 3.responsetime: 42.0 }
+
   - do:
       ml.preview_datafeed:
         body: >