Fail verification for subqueries

Author: felixbarny

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/plan/logical/promql/PromqlCommand.java

@@ -151,6 +151,9 @@ public void postAnalysisVerification(Failures failures) {
                     failures.add(fail(s, "offset modifiers are not supported at this time [{}]", s.sourceText()));
                 }
             }
+            if (lp instanceof Subquery) {
+                failures.add(fail(lp, "subqueries are not supported at this time [{}]", lp.sourceText()));
+            }
             if (step() != null && lp instanceof RangeSelector rs) {
                 Duration rangeDuration = (Duration) rs.range().fold(null);
                 if (rangeDuration.equals(step()) == false) {

x-pack/plugin/esql/src/test/java/org/elasticsearch/xpack/esql/analysis/promql/PromqlVerifierTests.java

@@ -49,13 +49,15 @@ public void testPromqlIllegalNameLabelMatcher() {
         );
     }
 
-    @Ignore
     public void testPromqlSubquery() {
-        // TODO doesn't parse
-        // line 1:36: Invalid query 'network.bytes_in'[ValueExpressionContext] given; expected Expression but found
-        // InstantSelector
-        assertThat(error("TS test | PROMQL step 5m (avg(rate(network.bytes_in[5m:])))", tsdb), equalTo(""));
-        assertThat(error("TS test | PROMQL step 5m (avg(rate(network.bytes_in[5m:1m])))", tsdb), equalTo(""));
+        assertThat(
+            error("TS test | PROMQL step 5m (avg(rate(network.bytes_in[5m:])))", tsdb),
+            equalTo("1:36: subqueries are not supported at this time [network.bytes_in[5m:]]")
+        );
+        assertThat(
+            error("TS test | PROMQL step 5m (avg(rate(network.bytes_in[5m:1m])))", tsdb),
+            equalTo("1:36: subqueries are not supported at this time [network.bytes_in[5m:1m]]")
+        );
     }
 
     @Ignore