fix: account for struct fields in VirtualTableScan check

core/src/main/java/io/substrait/relation/VirtualTableScan.java

@@ -3,6 +3,7 @@
 import io.substrait.expression.Expression;
 import io.substrait.type.NamedStruct;
 import io.substrait.type.Type;
+import io.substrait.type.TypeVisitor;
 import java.util.List;
 import org.immutables.value.Value;
 
@@ -30,7 +31,9 @@ protected void check() {
 
     assert rows.size() > 0
         && names.stream().noneMatch(s -> s == null)
-        && rows.stream().noneMatch(r -> r == null || r.fields().size() != names.size());
+        && rows.stream().noneMatch(r -> r == null)
+        && rows.stream()
+            .allMatch(r -> r.getType().accept(new NamedFieldCountingTypeVisitor()) == names.size());
   }
 
   @Override
@@ -46,4 +49,139 @@ public <O, E extends Exception> O accept(RelVisitor<O, E> visitor) throws E {
   public static ImmutableVirtualTableScan.Builder builder() {
     return ImmutableVirtualTableScan.builder();
   }
+
+  private static class NamedFieldCountingTypeVisitor
+      implements TypeVisitor<Integer, RuntimeException> {
+    @Override
+    public Integer visit(Type.Bool type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.I8 type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.I16 type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.I32 type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.I64 type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.FP32 type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.FP64 type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Str type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Binary type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Date type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Time type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.TimestampTZ type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Timestamp type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.PrecisionTimestamp type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.PrecisionTimestampTZ type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.IntervalYear type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.IntervalDay type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.UUID type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.FixedChar type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.VarChar type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.FixedBinary type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Decimal type) throws RuntimeException {
+      return 0;
+    }
+
+    @Override
+    public Integer visit(Type.Struct type) throws RuntimeException {
+      // Only struct fields have names - the top level column names are also
+      // captured by this since the whole schema is wrapped in a Struct type
+      return type.fields().stream().mapToInt(field -> 1 + field.accept(this)).sum();
+    }
+
+    @Override
+    public Integer visit(Type.ListType type) throws RuntimeException {
+      return type.elementType().accept(this);
+    }
+
+    @Override
+    public Integer visit(Type.Map type) throws RuntimeException {
+      return type.key().accept(this) + type.value().accept(this);
+    }
+
+    @Override
+    public Integer visit(Type.UserDefined type) throws RuntimeException {
+      return 0;
+    }
+  }
 }

core/src/test/java/io/substrait/relation/VirtualTableScanTest.java

@@ -0,0 +1,52 @@
+package io.substrait.relation;
+
+import static io.substrait.expression.ExpressionCreator.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+import io.substrait.expression.Expression;
+import java.util.HashMap;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class VirtualTableScanTest {
+
+  @Test
+  void check() {
+    VirtualTableScan virtualTableScan =
+        ImmutableVirtualTableScan.builder()
+            .addDfsNames(
+                "string",
+                "struct",
+                "struct_field1",
+                "struct_field2",
+                "list",
+                "list_struct_field1",
+                "map",
+                "map_key_struct_field1",
+                "map_value_struct_field1")
+            .addRows(
+                struct(
+                    false,
+                    string(false, "string_val"),
+                    struct(
+                        false,
+                        string(false, "struct_field1_val"),
+                        string(false, "struct_field2_val")),
+                    list(false, struct(false, string(false, "list_struct_field1_val"))),
+                    map(
+                        false,
+                        mapOf(
+                            struct(false, string(false, "map_key_struct_field1_val")),
+                            struct(false, string(false, "map_value_struct_field1_val"))))))
+            .build();
+    assertDoesNotThrow(virtualTableScan::check);
+  }
+
+  private Map<Expression.Literal, Expression.Literal> mapOf(
+      Expression.Literal key, Expression.Literal value) {
+    // Map.of() comes only in Java 9 and the "core" module is on Java 8
+    HashMap<Expression.Literal, Expression.Literal> map = new HashMap<>();
+    map.put(key, value);
+    return map;
+  }
+}