Add a test of an edge case for the set processor (elastic#134217)

Author: joegallo

modules/ingest-common/src/yamlRestTest/resources/rest-api-spec/test/ingest/270_set_processor.yml

@@ -6,7 +6,7 @@ teardown:
         ignore: 404
 
 ---
-"Test set processor with template value":
+"Test set processor with a templated value":
   - do:
       ingest.put_pipeline:
         id: "1"
@@ -53,6 +53,7 @@ teardown:
         index: test
         id: "2"
   - match: { _source.foo: "hello" }
+
 ---
 "Test set processor with index change and require_alias":
   - do:
@@ -295,3 +296,38 @@ teardown:
   - match: { _source.result_2: "{{bar}}" }
   - match: { _source.old_bar: 2 }
   - match: { _source.bar: 3 }
+
+---
+"Test set processor with ignore_empty_value and a literal empty value":
+  - do:
+      ingest.put_pipeline:
+        id: "1"
+        body:  >
+          {
+            "processors": [
+              {
+                "set" : {
+                  "description": "we don't forbid this, even though it's a little silly",
+                  "field" : "foo",
+                  "value" : "",
+                  "ignore_empty_value" : true
+                }
+              }
+            ]
+          }
+  - match: { acknowledged: true }
+
+  - do:
+      index:
+        index: test
+        id: "1"
+        pipeline: "1"
+        body: {
+          foo: "hello"
+        }
+
+  - do:
+      get:
+        index: test
+        id: "1"
+  - match: { _source.foo: "" }