automake: new option 'serial-tests'

Currently, automake offers a 'parallel-tests' option to enable the
use of the parallel testsuite harness in the generated Makefiles,
but no option to explicitly state the intention of using the older
serial testsuite driver (which is currently the default).

This makes the parallel test harness seems like a second-class
citizen (while actually it should be the other way around); more
importantly, it will prevent us from making the parallel harness
be the default one in future automake versions, since the users
of the serial harness would then have no way to instruct automake
to continue using it.

We solve all of this by introducing a new 'serial-tests' option.

* lib/Automake/Options.pm (_process_option_list): Recognize the
new option, and related minor refactoring.
* tests/serial-tests.test: New test.
* tests/list-of-tests.mk: Add it.
* doc/automake.texi: Update.
* NEWS: Likewise.

1 files changed, 17 insertions, 7 deletions

diff --git a/doc/automake.texi b/doc/automake.texi
index f342686ee..3e6a2bf6a 100644
--- a/doc/automake.texi
+++ b/doc/automake.texi
@@ -8927,15 +8927,18 @@ by the tests, not the tests themselves.  Of course you can set
 
 @node Serial Test Harness
 @subsection Serial Test Harness
+@cindex @option{serial-tests}, Using
 
 @emph{NOTE:} This harness, while still being the default one, is
-obsolescent, and kept mostly for backward-compatibility reasons.
-The user is advised to use the parallel test harness instead
-(@pxref{Parallel Test Harness}).
-
-The serial harness operates by simply running the tests serially, one at
-the time, without any I/O redirection.  It's up to the user to implement
-logging of tests' output, if that's requited or desired.
+obsolescent, and kept mostly for backward-compatibility reasons.  The user
+is advised to use the parallel test harness instead (@pxref{Parallel Test
+Harness}).  Be warned that future Automake versions might switch to use
+that more modern and feature-rich harness by default.
+
+The serial test harness is enabled by the Automake option
+@option{serial-tests}. It operates by simply running the tests serially,
+one at the time, without any I/O redirection.  It's up to the user to
+implement logging of tests' output, if that's requited or desired.
 @c TODO: give an example of how this can be done.
 
 For historical and implementation reasons, the @code{AM_TESTS_ENVIRONMENT}
@@ -10139,6 +10142,13 @@ this directory.
 Enable test suite harness for @code{TESTS} that can run tests in parallel
 (@pxref{Parallel Test Harness}, for more information).
 
+@item @option{serial-tests}
+@cindex Option, @option{serial-tests}
+@opindex serial-tests
+Enable the older serial test suite harness for @code{TESTS} (@pxref{Serial
+Test Harness}, for more information).  This is still the default for the
+moment.
+
 @item @option{readme-alpha}
 @cindex Option, @option{readme-alpha}
 @opindex readme-alpha