fix: untyped null parameters would cause NPE

Adding an untyped null value as a parameter to a statement was not
possible, as:
1. The parameter collection would allow a null value to be added, but
   when the statement was built, it would throw a NullPointerException
   because it used an ImmutableMap internally, which does not support
   null values.
2. The translation from a hand-written Statement instance to a proto
   Statement instance would fail, as it did not take into account that
   the parameter could be null.

Fixes #1679

google-cloud-spanner/src/main/java/com/google/cloud/spanner/AbstractReadContext.java

@@ -583,8 +583,10 @@ ExecuteSqlRequest.Builder getExecuteSqlRequestBuilder(
     if (!stmtParameters.isEmpty()) {
       com.google.protobuf.Struct.Builder paramsBuilder = builder.getParamsBuilder();
       for (Map.Entry<String, Value> param : stmtParameters.entrySet()) {
-        paramsBuilder.putFields(param.getKey(), param.getValue().toProto());
-        builder.putParamTypes(param.getKey(), param.getValue().getType().toProto());
+        paramsBuilder.putFields(param.getKey(), Value.toProto(param.getValue()));
+        if (param.getValue() != null) {
+          builder.putParamTypes(param.getKey(), param.getValue().getType().toProto());
+        }
       }
     }
     if (withTransactionSelector) {
@@ -612,10 +614,12 @@ ExecuteBatchDmlRequest.Builder getExecuteBatchDmlRequestBuilder(
         com.google.protobuf.Struct.Builder paramsBuilder =
             builder.getStatementsBuilder(idx).getParamsBuilder();
         for (Map.Entry<String, Value> param : stmtParameters.entrySet()) {
-          paramsBuilder.putFields(param.getKey(), param.getValue().toProto());
-          builder
-              .getStatementsBuilder(idx)
-              .putParamTypes(param.getKey(), param.getValue().getType().toProto());
+          paramsBuilder.putFields(param.getKey(), Value.toProto(param.getValue()));
+          if (param.getValue() != null) {
+            builder
+                .getStatementsBuilder(idx)
+                .putParamTypes(param.getKey(), param.getValue().getType().toProto());
+          }
         }
       }
       idx++;

google-cloud-spanner/src/main/java/com/google/cloud/spanner/BatchClientImpl.java

@@ -169,8 +169,10 @@ public List<Partition> partitionQuery(
       if (!stmtParameters.isEmpty()) {
         Struct.Builder paramsBuilder = builder.getParamsBuilder();
         for (Map.Entry<String, Value> param : stmtParameters.entrySet()) {
-          paramsBuilder.putFields(param.getKey(), param.getValue().toProto());
-          builder.putParamTypes(param.getKey(), param.getValue().getType().toProto());
+          paramsBuilder.putFields(param.getKey(), Value.toProto(param.getValue()));
+          if (param.getValue() != null) {
+            builder.putParamTypes(param.getKey(), param.getValue().getType().toProto());
+          }
         }
       }
       TransactionSelector selector = getTransactionSelector();

google-cloud-spanner/src/main/java/com/google/cloud/spanner/PartitionedDmlTransaction.java

@@ -217,8 +217,10 @@ private void setParameters(
     if (!statementParameters.isEmpty()) {
       com.google.protobuf.Struct.Builder paramsBuilder = requestBuilder.getParamsBuilder();
       for (Map.Entry<String, Value> param : statementParameters.entrySet()) {
-        paramsBuilder.putFields(param.getKey(), param.getValue().toProto());
-        requestBuilder.putParamTypes(param.getKey(), param.getValue().getType().toProto());
+        paramsBuilder.putFields(param.getKey(), Value.toProto(param.getValue()));
+        if (param.getValue() != null) {
+          requestBuilder.putParamTypes(param.getKey(), param.getValue().getType().toProto());
+        }
       }
     }
   }

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Statement.java

@@ -21,9 +21,9 @@
 
 import com.google.cloud.spanner.ReadContext.QueryAnalyzeMode;
 import com.google.common.base.Preconditions;
-import com.google.common.collect.ImmutableMap;
 import com.google.spanner.v1.ExecuteSqlRequest.QueryOptions;
 import java.io.Serializable;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
@@ -56,11 +56,11 @@
 public final class Statement implements Serializable {
   private static final long serialVersionUID = -1967958247625065259L;
 
-  private final ImmutableMap<String, Value> parameters;
+  private final Map<String, Value> parameters;
   private final String sql;
   private final QueryOptions queryOptions;
 
-  private Statement(String sql, ImmutableMap<String, Value> parameters, QueryOptions queryOptions) {
+  private Statement(String sql, Map<String, Value> parameters, QueryOptions queryOptions) {
     this.sql = sql;
     this.parameters = parameters;
     this.queryOptions = queryOptions;
@@ -112,14 +112,17 @@ public ValueBinder<Builder> bind(String parameter) {
     public Statement build() {
       checkState(
           currentBinding == null, "Binding for parameter '%s' is incomplete.", currentBinding);
-      return new Statement(sqlBuffer.toString(), ImmutableMap.copyOf(parameters), queryOptions);
+      return new Statement(
+          sqlBuffer.toString(),
+          Collections.unmodifiableMap(new HashMap<>(parameters)),
+          queryOptions);
     }
 
     private class Binder extends ValueBinder<Builder> {
       @Override
       Builder handle(Value value) {
         Preconditions.checkArgument(
-            !value.isCommitTimestamp(),
+            value == null || !value.isCommitTimestamp(),
             "Mutation.COMMIT_TIMESTAMP cannot be bound as a query parameter");
         checkState(currentBinding != null, "No binding in progress");
         parameters.put(currentBinding, value);
@@ -218,7 +221,11 @@ StringBuilder toString(StringBuilder b) {
           b.append(", ");
         }
         b.append(parameter.getKey()).append(": ");
-        parameter.getValue().toString(b);
+        if (parameter.getValue() == null) {
+          b.append("NULL");
+        } else {
+          parameter.getValue().toString(b);
+        }
       }
       b.append("}");
     }

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Value.java

@@ -73,6 +73,9 @@ public abstract class Value implements Serializable {
    */
   public static final Timestamp COMMIT_TIMESTAMP = Timestamp.ofTimeMicroseconds(0L);
 
+  static final com.google.protobuf.Value NULL_PROTO =
+      com.google.protobuf.Value.newBuilder().setNullValue(NullValue.NULL_VALUE).build();
+
   /** Constant to specify a PG Numeric NaN value. */
   public static final String NAN = "NaN";
 
@@ -622,6 +625,10 @@ public String toString() {
 
   // END OF PUBLIC API.
 
+  static com.google.protobuf.Value toProto(Value value) {
+    return value == null ? NULL_PROTO : value.toProto();
+  }
+
   abstract void toString(StringBuilder b);
 
   abstract com.google.protobuf.Value toProto();
@@ -737,9 +744,6 @@ Value newValue(boolean isNull, BitSet nulls, boolean[] values) {
 
   /** Template class for {@code Value} implementations. */
   private abstract static class AbstractValue extends Value {
-    static final com.google.protobuf.Value NULL_PROTO =
-        com.google.protobuf.Value.newBuilder().setNullValue(NullValue.NULL_VALUE).build();
-
     private final boolean isNull;
     private final Type type;
 

google-cloud-spanner/src/test/java/com/google/cloud/spanner/StatementTest.java

@@ -61,6 +61,8 @@ public void serialization() {
             .append("bytes_field = @bytes_field ")
             .bind("bytes_field")
             .to(ByteArray.fromBase64("abcd"))
+            .bind("untyped_null_field")
+            .to((Value) null)
             .build();
     reserializeAndAssert(stmt);
   }
@@ -165,6 +167,9 @@ public void equalsAndHashCode() {
     tester.addEqualityGroup(Statement.newBuilder("SELECT @x, @y").bind("y").to(2).build());
     tester.addEqualityGroup(
         Statement.newBuilder("SELECT @x, @y").bind("x").to(1).bind("y").to(2).build());
+    tester.addEqualityGroup(
+        Statement.newBuilder("SELECT @x, @y").bind("x").to((Value) null).build(),
+        Statement.newBuilder("SELECT @x, @y").bind("x").to((Value) null).build());
     tester.testEquals();
   }
 }

google-cloud-spanner/src/test/java/com/google/cloud/spanner/it/ITDMLTest.java

@@ -18,7 +18,12 @@
 
 import static com.google.cloud.spanner.testing.EmulatorSpannerHelper.isUsingEmulator;
 import static com.google.common.truth.Truth.assertThat;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
 import static org.junit.Assert.fail;
+import static org.junit.Assume.assumeFalse;
 
 import com.google.cloud.spanner.AbortedException;
 import com.google.cloud.spanner.Database;
@@ -38,6 +43,7 @@
 import com.google.cloud.spanner.TimestampBound;
 import com.google.cloud.spanner.TransactionRunner;
 import com.google.cloud.spanner.TransactionRunner.TransactionCallable;
+import com.google.cloud.spanner.Value;
 import com.google.cloud.spanner.connection.ConnectionOptions;
 import java.util.ArrayList;
 import java.util.Arrays;
@@ -380,4 +386,41 @@ public void standardDMLWithExecuteSQL() {
     // checks for multi-stmts within a txn, therefore also verifying seqNo.
     executeQuery(DML_COUNT * 2, updateDml(), deleteDml());
   }
+
+  @Test
+  public void testUntypedNullValues() {
+    assumeFalse(
+        "Spanner PostgreSQL does not yet support untyped null values",
+        dialect.dialect == Dialect.POSTGRESQL);
+
+    DatabaseClient client = getClient(dialect.dialect);
+    String sql;
+    if (dialect.dialect == Dialect.POSTGRESQL) {
+      sql = "INSERT INTO T (K, V) VALUES ($1, $2)";
+    } else {
+      sql = "INSERT INTO T (K, V) VALUES (@p1, @p2)";
+    }
+    Long updateCount =
+        client
+            .readWriteTransaction()
+            .run(
+                transaction ->
+                    transaction.executeUpdate(
+                        Statement.newBuilder(sql)
+                            .bind("p1")
+                            .to("k1")
+                            .bind("p2")
+                            .to((Value) null)
+                            .build()));
+
+    assertNotNull(updateCount);
+    assertEquals(1L, updateCount.longValue());
+
+    // Read the row back and verify that the value is null.
+    try (ResultSet resultSet = client.singleUse().executeQuery(Statement.of("SELECT V FROM T"))) {
+      assertTrue(resultSet.next());
+      assertTrue(resultSet.isNull(0));
+      assertFalse(resultSet.next());
+    }
+  }
 }