Fix for Bug#56817 - mysqlhotcopy tests fail when DBI and DBD-mysql perl modules are not found

Third updated patch - this version also includes copyright notice in added Perl script.
This patch implements a check for such modules at runtime. If modules are not found or unable to load, the test is skipped with 
the following message:
            
            [ skipped ]  Test needs Perl modules DBI and DBD::mysql
            
Checks are done via a helper Perl script which looks for the module in a runtime environment that is as similar to that of the 
mysqlhotcopy script as possible (thus not intended for Windows environments at this time).
The helper script tells mysql-test about the result by writing information to a temporary file that is later read by mysql-test.
See comments in added files (have_dbi_dbd-mysql.inc and checkDBI_DBD-mysql.pl) for details.
The patch also removes the mysqlhotcopy tests from the list of disabled tests.

mysql-test/include/have_dbi_dbd-mysql.inc

+#
+# Originally created by John Embretsen, 2011-01-26.
+#
+# Checks for the existence of Perl modules DBI and DBD::mysql as seen from the
+# perl installation used by "external" executable perl scripts, i.e. scripts
+# that are executed as standalone scripts interpreted by the perl installation
+# specified by the "shebang" line in the top of these scripts.
+#
+# If either module is not found, the test will be skipped.
+#
+# For use in tests that call perl scripts that require these modules.
+#
+# This file is intended to work on Unix. Windows may need different treatment.
+# Reasoning:
+#   - "shebangs" are not relevant on Windows, but need to be handled here.
+#   - Perl scripts cannot be made executable on Windows, interpreter must be 
+#     specified.
+#
+# Note that if there are multiple perl installations and not all have the
+# required modules, this check may fail even if the perl in path does have
+# the modules available. This may happen if the perl specified by the script's 
+# shebang (e.g. #!/usr/bin/perl) does not have these modules, and script is 
+# called without specifying the perl interpreter. However, this will be 
+# a correct result in cases where a test calls a script with a similar shebang.
+#
+################################################################################
+
+--source include/not_windows.inc
+
+# We jump through some hoops since there is no direct way to check if an 
+# external command went OK or not from a mysql-test file:
+#
+#   - In theory, we could do as simple as "exec perl -MDBI -MDBD::mysql -e 1",
+#     however we cannot check the result (exit code) from within a test script. 
+#     Also, this may not yield the same result as other uses of perl due to the 
+#     shebang issue mentioned above.
+#   - Instead we use a separate helper perl script that checks for the modules.
+#   - If the modules are found, the perl script leaves a file which sets a
+#     variable that can be read by this file.
+#     If the modules are not found, the perl script does not set this variable,
+#     but leaves an empty file instead.
+#
+# This is done because there is apparently no direct way to transfer
+# information from perl to the test script itself.
+
+--disable_query_log
+--disable_result_log
+--disable_warnings
+
+# We do not use embedded perl in this script because that would not have yielded
+# correct results for a situation where an external Perl script is called like
+# "scriptname" instead of "perl scriptname" and the shebang in the script points
+# to a specific perl that may be different than the perl in PATH.
+#
+# Instead, we call a separate helper script which checks for the modules in its
+# own environment. We call it without "perl" in front.
+
+--let $perlChecker= $MYSQLTEST_VARDIR/std_data/checkDBI_DBD-mysql.pl
+--let $resultFile= $MYSQL_TMP_DIR/dbidbd-mysql.txt
+
+# Make the script executable and execute it.
+--chmod 0755 $perlChecker
+--exec $perlChecker
+
+# Source the resulting temporary file and look for a variable being set.
+--source $resultFile
+
+if (!$dbidbd) {
+    --skip Test needs Perl modules DBI and DBD::mysql
+} 
+
+# Clean up
+--remove_file $resultFile
+
+--enable_query_log
+--enable_result_log
+--enable_warnings
+

mysql-test/include/mysqlhotcopy.inc

@@ -4,12 +4,26 @@
 
 --source include/not_windows.inc
 --source include/not_embedded.inc
+--source include/have_dbi_dbd-mysql.inc
 
 if (!$MYSQLHOTCOPY)
 {
+  # Fail the test if the mysqlhotcopy script is missing.
+  # If the tool's location changes, mysql-test-run.pl must be updated to
+  # reflect this (look for "MYSQLHOTCOPY").
   die due to missing mysqlhotcopy tool;
 }
 
+# NOTE (johnemb, 2011-01-26):
+#       In this test mysqlhotcopy (a perl script) is executed as a standalone
+#       executable, i.e. not necessarily using the perl interpreter in PATH,
+#       because that is how the documentation demonstrates it.
+#
+#       We include have_dbi_dbd-mysql.inc above so that the test will
+#       be skipped if Perl modules required by the mysqlhotcopy tool are not
+#       found when the script is run this way.
+
+
 let $MYSQLD_DATADIR= `SELECT @@datadir`;
 --disable_warnings
 DROP DATABASE IF EXISTS hotcopy_test;

mysql-test/std_data/checkDBI_DBD-mysql.pl

+#!/usr/bin/perl
+
+# Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Library General Public
+# License as published by the Free Software Foundation; version 2
+# of the License.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Library General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+
+################################################################################
+#
+# This perl script checks for availability of the Perl modules DBI and
+# DBD::mysql using the "current" perl interpreter.
+#
+# Useful for test environment checking before testing executable perl scripts
+# in the MySQL Server distribution.
+#
+# NOTE: The "shebang" on the first line of this script should always point to
+#       /usr/bin/perl, so that we can use this script to check whether or not we
+#       support running perl scripts with such a shebang without specifying the
+#       perl interpreter on the command line. Such a script is mysqlhotcopy.
+#
+#       When run as "checkDBI_DBD-mysql.pl" the shebang line will be evaluated
+#       and used. When run as "perl checkDBI_DBD-mysql.pl" the shebang line is
+#       not used.
+#
+# NOTE: This script will create a temporary file in MTR's tmp dir.
+#       If modules are found, a mysql-test statement which sets a special
+#       variable is written to this file. If one of the modules is not found
+#       (or cannot be loaded), the file will remain empty.
+#       A test (or include file) which sources that file can then easily do
+#       an if-check on the special variable to determine success or failure.
+#
+#       Example:
+#
+#         --let $perlChecker= $MYSQLTEST_VARDIR/std_data/checkDBI_DBD-mysql.pl
+#         --let $resultFile= $MYSQL_TMP_DIR/dbidbd-mysql.txt
+#         --chmod 0755 $perlChecker
+#         --exec $perlChecker
+#         --source $resultFile
+#         if (!$dbidbd) {
+#             --skip Test needs Perl modules DBI and DBD::mysql
+#         } 
+#
+#       The calling script is also responsible for cleaning up after use:
+#
+#         --remove_file $resultFile
+#
+# Windows notes: 
+#   - shebangs may work differently - call this script with "perl " in front.
+#
+# See mysql-test/include/have_dbi_dbd-mysql.inc for example use of this script.
+# This script should be executable for the user running MTR.
+#
+################################################################################
+
+BEGIN {
+    # By using eval inside BEGIN we can suppress warnings and continue after.
+    # We need to catch "Can't locate" as well as "Can't load" errors.
+    eval{
+        $FOUND_DBI=0;
+        $FOUND_DBD_MYSQL=0;
+
+        # Check for DBI module:
+        $FOUND_DBI=1 if require DBI;
+
+        # Check for DBD::mysql module
+        $FOUND_DBD_MYSQL=1 if require DBD::mysql;
+    };
+};
+
+# Open a file to be used for transfer of result back to mysql-test.
+# The file must be created whether we write to it or not, otherwise mysql-test 
+# will complain if trying to source it. 
+# An empty file indicates failure to load modules.
+open(FILE, ">", $ENV{'MYSQL_TMP_DIR'}.'/dbidbd-mysql.txt');
+
+if ($FOUND_DBI && $FOUND_DBD_MYSQL) {
+    # write a mysql-test command setting a variable to indicate success
+    print(FILE 'let $dbidbd= FOUND_DBI_DBD-MYSQL;'."\n");
+}
+
+# close the file.
+close(FILE);
+
+1;
+

mysql-test/t/disabled.def

@@ -11,7 +11,5 @@
 ##############################################################################
 kill                     : Bug#37780 2008-12-03 HHunger need some changes to be robust enough for pushbuild.
 query_cache_28249        : Bug#43861 2009-03-25 main.query_cache_28249 fails sporadically
-main.mysqlhotcopy_myisam : Bug#56817 2010-10-21 anitha mysqlhotcopy* fails
-main.mysqlhotcopy_archive: Bug#56817 2010-10-21 anitha mysqlhotcopy* fails
 log_tables-big           : Bug#48646 2010-11-15 mattiasj report already exists
 read_many_rows_innodb    : Bug#37635 2010-11-15 mattiasj report already exists