[CALCITE-4177] Throw exception when deserialize SqlOperator fails, do not return null

core/src/main/java/org/apache/calcite/rel/externalize/RelJson.java

@@ -75,6 +75,7 @@
 import java.util.Set;
 
 import static org.apache.calcite.rel.RelDistributions.EMPTY;
+import static org.apache.calcite.util.Static.RESOURCE;
 
 /**
  * Utilities for converting {@link org.apache.calcite.rel.RelNode}
@@ -678,7 +679,7 @@ SqlOperator toOp(Map<String, Object> map) {
     if (class_ != null) {
       return AvaticaUtils.instantiatePlugin(SqlOperator.class, class_);
     }
-    return null;
+    throw RESOURCE.noOperator(name, kind, syntax).ex();
   }
 
   SqlAggFunction toAggregation(Map<String, Object> map) {

core/src/main/java/org/apache/calcite/runtime/CalciteResource.java

@@ -931,4 +931,7 @@ ExInst<CalciteException> invalidTypesForComparison(String clazzName0, String op,
 
   @BaseMessage("Different length for bitwise operands: the first: {0,number,#}, the second: {1,number,#}")
   ExInst<CalciteException> differentLengthForBitwiseOperands(int l0, int l1);
+
+  @BaseMessage("No operator for ''{0}'' with kind: ''{1}'', syntax: ''{2}'' during JSON deserialization")
+  ExInst<CalciteException> noOperator(String name, String kind, String syntax);
 }

core/src/main/resources/org/apache/calcite/runtime/CalciteResource.properties

@@ -305,4 +305,5 @@ InvalidInputForExtractValue=Invalid input for EXTRACTVALUE: xml: ''{0}'', xpath
 InvalidInputForExtractXml=Invalid input for EXTRACT xpath: ''{0}'', namespace: ''{1}''
 InvalidInputForExistsNode=Invalid input for EXISTSNODE xpath: ''{0}'', namespace: ''{1}''
 DifferentLengthForBitwiseOperands=Different length for bitwise operands: the first: {0,number,#}, the second: {1,number,#}
+NoOperator=No operator for ''{0}'' with kind: ''{1}'', syntax: ''{2}'' during JSON deserialization
 # End CalciteResource.properties

core/src/test/java/org/apache/calcite/plan/RelWriterTest.java

@@ -81,6 +81,7 @@
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 /**
  * Unit test for {@link org.apache.calcite.rel.externalize.RelJson}.
@@ -1131,6 +1132,32 @@ private RelNode mockCountOver(String table,
     assertThat(s, isLinux(expected));
   }
 
+  @Test void testDeserializeInvalidOperatorName() {
+    final FrameworkConfig config = RelBuilderTest.config().build();
+    final RelBuilder builder = RelBuilder.create(config);
+    final RelNode rel = builder
+        .scan("EMP")
+        .project(
+            builder.field("JOB"),
+            builder.field("SAL"))
+        .aggregate(
+            builder.groupKey("JOB"),
+            builder.max("max_sal", builder.field("SAL")),
+            builder.min("min_sal", builder.field("SAL")))
+        .project(
+            builder.field("max_sal"),
+            builder.field("min_sal"))
+        .build();
+    final RelJsonWriter jsonWriter = new RelJsonWriter();
+    rel.explain(jsonWriter);
+    // mock a non exist SqlOperator
+    String relJson = jsonWriter.asString().replace("\"name\": \"MAX\"", "\"name\": \"MAXS\"");
+    assertThrows(RuntimeException.class,
+        () -> deserializeAndDumpToTextFormat(getSchema(rel), relJson),
+        "org.apache.calcite.runtime.CalciteException: "
+            + "No operator for 'MAXS' with kind: 'MAX', syntax: 'FUNCTION' during JSON deserialization");
+  }
+
   private RelNode createSortPlan(RelDistribution distribution) {
     final FrameworkConfig config = RelBuilderTest.config().build();
     final RelBuilder builder = RelBuilder.create(config);