On Tue, Jan 26, 2016 at 5:15 AM, Junio C Hamano <gitster@xxxxxxxxx> wrote:
> Eric Sunshine <sunshine@xxxxxxxxxxxxxx> writes:
>
>>> + git for-each-ref --format="|%(align:$option)refname is %(refname)%(end)|%(refname)" >actual &&
>>
>> This is not wrong, per se, but referencing $option inside the
>> non-interpolating single-quote context of the test body makes it a bit
>> harder to understand than it need be. As it is, at the time that the
>> test body actually gets executed, $option still evaluates to the
>> desired permutation value so it works.
>
> I think I said this in one of my recent reviews to somebody else,
> but this needs repeating.
>
> My position on this has been and still is a complete opposite. It
> is a designed behaviour that variable references made inside test
> body that is quoted with sq pair can see the values of the variables
> that are defined outside test_expect_success, and you can freely use
> the global $TRASH_DIRECTORY, $_x40, etc. inside the test body that
> is quoted with single quote. The $option here is no different.
>
> In fact, it is more desirable to avoid double-quoting the test body.
> The problem with using double-quote around the test body and
> formulating the executable shell script using variable interpolation
> before test_expect_success even runs is that you would be tempted to
> do something silly like this:
>
> HEAD_SHA1=$(git rev-parse --verify HEAD)
>
> test_expect_success "check something" "
> HEAD_SHA1=$(git rev-parse --verify HEAD) &&
> ... do other things that should not move the HEAD ... &&
> test '$(git rev-parse HEAD)' = '$HEAD_SHA1' &&
> test '$SOME_VAR' = '$OTHER_VAR' &&
> "
>
> It is not just error prone (if variable reference had a shell
> metacharacter in it, e.g. a single-quote in OTHER_VAR's value, you'd
> have a syntax error in the test body), but because two invocations
> of rev-parse in the above are both made before test_expect_success
> runs, and would yield the same value. It is not even testing the
> right thing. If you broke rev-parse, the invocation will not fail
> inside test_expect_success but outside when the arguments to that
> helper is being prepared.
>
> So please do not write something like this:
>
>> test_align_permutations () {
>> while ...
>> do
>> test_expect_success "align:$option" "
>> git for-each-ref --format='...$option...' >actual &&
>> ...
>> "
>> done
>> }
>
> but make it more like this:
>
> for option in ...
> do
> test_expect_success "align:$option" '
> git for-each-ref --format="...$option..." &&
> ...
> '
> done
>
Thanks for this descriptive explanation, I shall use the suggested format.
--
Regards,
Karthik Nayak
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