[ES|QL] RERANK command default inferenceId (elastic#128685)

* [ES|QL] Make inferenceId optional for the `RERANK` command (default to `.rerank-v1-elasticsearch`)

* lint

* Remove old test.

* Fix failing test

Author: afoucret

x-pack/plugin/esql/src/main/antlr/EsqlBaseParser.g4

@@ -378,7 +378,7 @@ joinPredicate
     ;
 
 rerankCommand
-    : DEV_RERANK queryText=constant ON rerankFields WITH inferenceId=identifierOrParameter
+    : DEV_RERANK queryText=constant ON rerankFields (WITH inferenceId=identifierOrParameter)?
     ;
 
 completionCommand

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/EsqlBaseParser.interp

@@ -662,7 +662,11 @@ public PlanFactory visitRerankCommand(EsqlBaseParser.RerankCommandContext ctx) {
             );
         }
 
-        return p -> new Rerank(source, p, inferenceId(ctx.inferenceId), queryText, visitRerankFields(ctx.rerankFields()));
+        Literal inferenceId = ctx.inferenceId != null
+            ? inferenceId(ctx.inferenceId)
+            : new Literal(source, Rerank.DEFAULT_INFERENCE_ID, KEYWORD);
+
+        return p -> new Rerank(source, p, inferenceId, queryText, visitRerankFields(ctx.rerankFields()));
     }
 
     @Override

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/EsqlBaseParser.java

@@ -41,6 +41,7 @@
 public class Rerank extends InferencePlan<Rerank> implements SortAgnostic, SurrogateLogicalPlan, TelemetryAware {
 
     public static final NamedWriteableRegistry.Entry ENTRY = new NamedWriteableRegistry.Entry(LogicalPlan.class, "Rerank", Rerank::new);
+    public static final Object DEFAULT_INFERENCE_ID = ".rerank-v1-elasticsearch";
     private final Attribute scoreAttribute;
     private final Expression queryText;
     private final List<Alias> rerankFields;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/parser/LogicalPlanBuilder.java

@@ -3179,7 +3179,10 @@ public void testResolveRerankFields() {
                     | RERANK "food" ON title, SUBSTRING(description, 0, 100), yearRenamed=year WITH `reranking-inference-id`
                     """, "mapping-books.json");
             } catch (ParsingException ex) {
-                assertThat(ex.getMessage(), containsString("line 3:36: mismatched input '(' expecting {'=', ',', '.', 'with'}"));
+                assertThat(
+                    ex.getMessage(),
+                    containsString("line 3:36: mismatched input '(' expecting {<EOF>, '|', '=', ',', '.', 'with'}")
+                );
             }
         }
 

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plan/logical/inference/Rerank.java

@@ -3220,6 +3220,17 @@ public void testInvalidJoinPatterns() {
         }
     }
 
+    public void testRerankDefaultInferenceId() {
+        assumeTrue("RERANK requires corresponding capability", EsqlCapabilities.Cap.RERANK.isEnabled());
+
+        var plan = processingCommand("RERANK \"query text\" ON title");
+        var rerank = as(plan, Rerank.class);
+
+        assertThat(rerank.inferenceId(), equalTo(literalString(".rerank-v1-elasticsearch")));
+        assertThat(rerank.queryText(), equalTo(literalString("query text")));
+        assertThat(rerank.rerankFields(), equalTo(List.of(alias("title", attribute("title")))));
+    }
+
     public void testRerankSingleField() {
         assumeTrue("RERANK requires corresponding capability", EsqlCapabilities.Cap.RERANK.isEnabled());
 
@@ -3295,10 +3306,7 @@ public void testRerankWithNamedParameters() {
     public void testInvalidRerank() {
         assumeTrue("RERANK requires corresponding capability", EsqlCapabilities.Cap.RERANK.isEnabled());
         expectError("FROM foo* | RERANK ON title WITH inferenceId", "line 1:20: mismatched input 'ON' expecting {QUOTED_STRING");
-
         expectError("FROM foo* | RERANK \"query text\" WITH inferenceId", "line 1:33: mismatched input 'WITH' expecting 'on'");
-
-        expectError("FROM foo* | RERANK \"query text\" ON title", "line 1:41: mismatched input '<EOF>' expecting {'=', ',', '.', 'with'}");
     }
 
     public void testCompletionUsingFieldAsPrompt() {