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test: allow prerequisite to be evaluated lazily

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The test prerequisite mechanism is a useful way to allow some tests
in a test script to be skipped in environments that do not support
certain features (e.g. it is pointless to attempt checking how well
symbolic links are handled by Git on filesystems that do not support
them).  It is OK for commonly used prerequisites to be always tested
during start-up of a test script by having a codeblock that tests a
feature and calls test_set_prereq, but for an uncommon feature,
forcing 90% of scripts to pay the same probing overhead for
prerequisite they do not care about is wasteful.

Introduce a mechanism to probe the prerequiste lazily.  Changes are:

 - test_lazy_prereq () function, which takes the name of the
   prerequisite it probes and the script to probe for it, is
   added.  This only registers the name of the prerequiste that can
   be lazily probed and the script to eval (without running).

 - test_have_prereq() function (which is used by test_expect_success
   and also can be called directly by test scripts) learns to look
   at the list of prerequisites that can be lazily probed, and the
   prerequisites that have already been probed that way.  When asked
   for a prerequiste that can be but haven't been probed, the script
   registered with an earlier call to test_lazy_prereq is evaluated
   and the prerequisite is set.

 - test_run_lazy_prereq_() function is a helper to run the probe
   script with the same kind of sandbox as regular tests, helped by
   Jeff King.

Update the codeblock to probe and set SYMLINKS prerequisite using
the new mechanism as an example.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano 2012-07-26 15:50:45 -07:00
parent f3cfc3b271
commit 04083f278d
2 changed files with 46 additions and 3 deletions
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42
t/test-lib-functions.sh
View file

@ -224,6 +224,32 @@ test_set_prereq () {
satisfied_prereq="$satisfied_prereq$1 "
}
satisfied_prereq=" "
lazily_testable_prereq= lazily_tested_prereq=
# Usage: test_lazy_prereq PREREQ 'script'
test_lazy_prereq () {
lazily_testable_prereq="$lazily_testable_prereq$1 "
eval test_prereq_lazily_$1=\$2
}
test_run_lazy_prereq_ () {
script='
mkdir -p "$TRASH_DIRECTORY/prereq-test-dir" &&
(
cd "$TRASH_DIRECTORY/prereq-test-dir" &&'"$2"'
)'
say >&3 "checking prerequisite: $1"
say >&3 "$script"
test_eval_ "$script"
eval_ret=$?
rm -rf "$TRASH_DIRECTORY/prereq-test-dir"
if test "$eval_ret" = 0; then
say >&3 "prerequisite $1 ok"
else
say >&3 "prerequisite $1 not satisfied"
fi
return $eval_ret
}
test_have_prereq () {
# prerequisites can be concatenated with ','
@ -238,6 +264,22 @@ test_have_prereq () {
for prerequisite
do
case " $lazily_tested_prereq " in
*" $prerequisite "*)
;;
*)
case " $lazily_testable_prereq " in
*" $prerequisite "*)
eval "script=\$test_prereq_lazily_$prerequisite" &&
if test_run_lazy_prereq_ "$prerequisite" "$script"
then
test_set_prereq $prerequisite
fi
lazily_tested_prereq="$lazily_tested_prereq$prerequisite "
esac
;;
esac
total_prereq=$(($total_prereq + 1))
case "$satisfied_prereq" in
*" $prerequisite "*)

7
t/test-lib.sh
View file

@ -659,9 +659,10 @@ test_i18ngrep () {
fi
}
# test whether the filesystem supports symbolic links
ln -s x y 2>/dev/null && test -h y 2>/dev/null && test_set_prereq SYMLINKS
rm -f y
test_lazy_prereq SYMLINKS '
# test whether the filesystem supports symbolic links
ln -s x y && test -h y
'
# When the tests are run as root, permission tests will report that
# things are writable when they shouldn't be.