Tweak behavior of psql --single-transaction depending on ON_ERROR_STOP

This commit, in completion of 157f873, forces a ROLLBACK for
--single-transaction only when ON_ERROR_STOP is used when one of the
steps defined by -f/-c fails.  Hence, COMMIT is always used when
ON_ERROR_STOP is not set, ignoring the status code of the last action
taken in the set of switches specified by -c/-f (previously ROLLBACK
would have been issued even without ON_ERROR_STOP if the last step
failed, while COMMIT was issued if a step in-between failed as long as
the last step succeeded, leading to more inconsistency).

While on it, this adds much more test coverage in this area when not
using ON_ERROR_STOP with multiple switch patterns involving -c and -f
for query files, single queries and slash commands.

The behavior of ON_ERROR_STOP is arguably a bug, but there was no much
support for a backpatch to force a ROLLBACK on a step failure, so this
change is done only on HEAD for now.

Per discussion with Tom Lane and Kyotaro Horiguchi.

Discussion: https://postgr.es/m/Yqbc8bAdwnP02na4@paquier.xyz

doc/src/sgml/ref/psql-ref.sgml

@@ -584,7 +584,8 @@ EOF
         <application>psql</application> to issue a <command>BEGIN</command> command
         before the first such option and a <command>COMMIT</command> command after
         the last one, thereby wrapping all the commands into a single
-        transaction. If any of the commands fails, a
+        transaction. If any of the commands fails and the variable
+        <varname>ON_ERROR_STOP</varname> was set, a
         <command>ROLLBACK</command> command is sent instead. This ensures that
         either all the commands complete successfully, or no changes are
         applied.

src/bin/psql/startup.c

@@ -426,8 +426,13 @@ main(int argc, char *argv[])
 
 		if (options.single_txn)
 		{
-			res = PSQLexec((successResult == EXIT_SUCCESS) ?
+			/*
-						   "COMMIT" : "ROLLBACK");
+			 * Rollback the contents of the single transaction if the caller
+			 * has set ON_ERROR_STOP and one of the steps has failed.  This
+			 * check needs to match the one done a couple of lines above.
+			 */
+			res = PSQLexec((successResult != EXIT_SUCCESS && pset.on_error_stop) ?
+						   "ROLLBACK" : "COMMIT");
 			if (res == NULL)
 			{
 				if (pset.on_error_stop)

src/bin/psql/t/001_basic.pl

@@ -204,6 +204,8 @@ like(
 # query result.
 my $tempdir = PostgreSQL::Test::Utils::tempdir;
 $node->safe_psql('postgres', "CREATE TABLE tab_psql_single (a int);");
+
+# Tests with ON_ERROR_STOP.
 $node->command_ok(
 	[
 		'psql',                                   '-X',
@@ -212,11 +214,12 @@ $node->command_ok(
 		'INSERT INTO tab_psql_single VALUES (1)', '-c',
 		'INSERT INTO tab_psql_single VALUES (2)'
 	],
-	'--single-transaction and multiple -c switches');
+	'ON_ERROR_STOP, --single-transaction and multiple -c switches');
 my $row_count =
   $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
 is($row_count, '2',
-	'--single-transaction commits transaction, multiple -c switches');
+	'--single-transaction commits transaction, ON_ERROR_STOP and multiple -c switches'
+);
 
 $node->command_fails(
 	[
@@ -226,11 +229,12 @@ $node->command_fails(
 		'INSERT INTO tab_psql_single VALUES (3)', '-c',
 		"\\copy tab_psql_single FROM '$tempdir/nonexistent'"
 	],
-	'--single-transaction and multiple -c switches, error');
+	'ON_ERROR_STOP, --single-transaction and multiple -c switches, error');
 $row_count =
   $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
 is($row_count, '2',
-	'client-side error rolls back transaction, multiple -c switches');
+	'client-side error rolls back transaction, ON_ERROR_STOP and multiple -c switches'
+);
 
 # Tests mixing files and commands.
 my $copy_sql_file   = "$tempdir/tab_copy.sql";
@@ -244,11 +248,12 @@ $node->command_ok(
 		'ON_ERROR_STOP=1', '-f', $insert_sql_file,       '-f',
 		$insert_sql_file
 	],
-	'--single-transaction and multiple -f switches');
+	'ON_ERROR_STOP, --single-transaction and multiple -f switches');
 $row_count =
   $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
 is($row_count, '4',
-	'--single-transaction commits transaction, multiple -f switches');
+	'--single-transaction commits transaction, ON_ERROR_STOP and multiple -f switches'
+);
 
 $node->command_fails(
 	[
@@ -256,10 +261,61 @@ $node->command_fails(
 		'ON_ERROR_STOP=1', '-f', $insert_sql_file,       '-f',
 		$copy_sql_file
 	],
-	'--single-transaction and multiple -f switches, error');
+	'ON_ERROR_STOP, --single-transaction and multiple -f switches, error');
 $row_count =
   $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
 is($row_count, '4',
-	'client-side error rolls back transaction, multiple -f switches');
+	'client-side error rolls back transaction, ON_ERROR_STOP and multiple -f switches'
+);
+
+# Tests without ON_ERROR_STOP.
+# The last switch fails on \copy.  The command returns a failure and the
+# transaction commits.
+$node->command_fails(
+	[
+		'psql',                 '-X',
+		'--single-transaction', '-f',
+		$insert_sql_file,       '-f',
+		$insert_sql_file,       '-c',
+		"\\copy tab_psql_single FROM '$tempdir/nonexistent'"
+	],
+	'no ON_ERROR_STOP, --single-transaction and multiple -f/-c switches');
+$row_count =
+  $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
+is($row_count, '6',
+	'client-side error commits transaction, no ON_ERROR_STOP and multiple -f/-c switches'
+);
+
+# The last switch fails on \copy coming from an input file.  The command
+# returns a success and the transaction commits.
+$node->command_ok(
+	[
+		'psql',           '-X', '--single-transaction', '-f',
+		$insert_sql_file, '-f', $insert_sql_file,       '-f',
+		$copy_sql_file
+	],
+	'no ON_ERROR_STOP, --single-transaction and multiple -f switches');
+$row_count =
+  $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
+is($row_count, '8',
+	'client-side error commits transaction, no ON_ERROR_STOP and multiple -f switches'
+);
+
+# The last switch makes the command return a success, and the contents of
+# the transaction commit even if there is a failure in-between.
+$node->command_ok(
+	[
+		'psql',                                   '-X',
+		'--single-transaction',                   '-c',
+		'INSERT INTO tab_psql_single VALUES (5)', '-f',
+		$copy_sql_file,                           '-c',
+		'INSERT INTO tab_psql_single VALUES (6)'
+	],
+	'no ON_ERROR_STOP, --single-transaction and multiple -c switches');
+$row_count =
+  $node->safe_psql('postgres', 'SELECT count(*) FROM tab_psql_single');
+is($row_count, '10',
+	'client-side error commits transaction, no ON_ERROR_STOP and multiple -c switches'
+);
 
 done_testing();