chore: loosen restrictions setRetryAbortsInternally (#2924)

* chore: loosen restrictions setRetryAbortsInternally

Calling setRetryAbortsInternally(boolean) was unnecessarily strict, as there
is no reason why it should be disallowed to change the value while in
auto-commit mode and/or read-only mode. The fact that the flag does not have
any direct impact on those modes, does not mean that it should be disallowed
to set the value.

The fact that it was impossible to set the value while in auto-commit mode,
also means that it is impossible to disable it using a startup command for
a PostgreSQL connection to PGAdapter, as PGAdapter creates connections in
auto-commit mode.

* 🦉 Updates from OwlBot post-processor

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---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: olavloite

google-cloud-spanner/src/main/java/com/google/cloud/spanner/connection/ConnectionImpl.java

@@ -678,10 +678,6 @@ public void setStatementTag(String tag) {
    */
   private void checkSetRetryAbortsInternallyAvailable() {
     ConnectionPreconditions.checkState(!isClosed(), CLOSED_ERROR_MSG);
-    ConnectionPreconditions.checkState(isInTransaction(), "This connection has no transaction");
-    ConnectionPreconditions.checkState(
-        getTransactionMode() == TransactionMode.READ_WRITE_TRANSACTION,
-        "RetryAbortsInternally is only available for read-write transactions");
     ConnectionPreconditions.checkState(
         !isTransactionStarted(),
         "RetryAbortsInternally cannot be set after the transaction has started");

google-cloud-spanner/src/test/java/com/google/cloud/spanner/connection/ConnectionImplTest.java

@@ -1863,6 +1863,50 @@ public void testCheckResultTypeAllowed() {
     checkResultTypeAllowed(parser.parse(Statement.of(start)), allowedResultTypes);
   }
 
+  @Test
+  public void testSetRetryAbortsInternally() {
+    try (ConnectionImpl connection =
+        createConnection(
+            ConnectionOptions.newBuilder()
+                .setCredentials(NoCredentials.getInstance())
+                .setUri(URI)
+                .build())) {
+      assertFalse("Read-only should be disabled by default", connection.isReadOnly());
+      assertTrue("Autocommit should be enabled by default", connection.isAutocommit());
+      assertFalse(
+          "Retry aborts internally should be disabled by default on test connections",
+          connection.isRetryAbortsInternally());
+
+      // It should be possible to change this value also when in auto-commit mode.
+      connection.setRetryAbortsInternally(true);
+      assertTrue(connection.isRetryAbortsInternally());
+
+      // It should be possible to change this value also when in transactional mode, as long as
+      // there is no active transaction.
+      connection.setAutocommit(false);
+      connection.setRetryAbortsInternally(false);
+      assertFalse(connection.isRetryAbortsInternally());
+
+      // It should be possible to change the value when in read-only mode.
+      connection.setReadOnly(true);
+      connection.setRetryAbortsInternally(true);
+      assertTrue(connection.isRetryAbortsInternally());
+
+      // It should not be possible to change the value when there is an active transaction.
+      connection.setReadOnly(false);
+      connection.setAutocommit(false);
+      connection.execute(Statement.of(SELECT));
+      assertThrows(SpannerException.class, () -> connection.setRetryAbortsInternally(false));
+      // Verify that the value did not change.
+      assertTrue(connection.isRetryAbortsInternally());
+
+      // Rolling back the connection should allow us to set the property again.
+      connection.rollback();
+      connection.setRetryAbortsInternally(false);
+      assertFalse(connection.isRetryAbortsInternally());
+    }
+  }
+
   private void assertThrowResultNotAllowed(
       AbstractStatementParser parser, String sql, ImmutableSet<ResultType> allowedResultTypes) {
     SpannerException exception =