On Fri, Feb 09, 2018 at 03:42:34AM +0100, SZEDER Gábor wrote:
> To check that a git command fails and to inspect its error message we
> usually execute a command like this throughout our test suite:
>
> test_must_fail git command --option 2>output.err
>
> Note that this command doesn't limit the redirection to the git
> command, but it redirects the standard error of the 'test_must_fail'
> helper function as well. This is wrong for several reasons:
>
> - If that git command were to succeed or die for an unexpected
> reason e.g. signal, then 'test_must_fail's helpful error message
> would end up in the given file instead of on the terminal or in
> 't/test-results/$T.out', when the test is run with '-v' or
> '--verbose-log', respectively.
>
> - If the test is run with '-x', the trace of executed commands in
> 'test_must_fail' will go to stderr as well (except for more recent
> Bash versions supporting $BASH_XTRACEFD), and then in turn will
> end up in the given file.
I have to admit that I'm slightly negative on this approach, just
because:
1. It requires every caller to do something special, rather than just
using normal redirection. And the feature isn't as powerful as
redirection. E.g., some callers do:
test_must_fail foo >output 2>&1
But:
test_must_fail stderr=output foo >output
is not quite right (stdout and stderr outputs may clobber each
other, because they have independent position pointers).
2. The "-x" problems aren't specific to test_must_fail at all. They're
a general issue with shell functions.
I'm not entirely happy with saying "if you want to use -x, please use
bash". But given that it actually solves the problems everywhere with no
further effort, is it really that bad a solution?
For the error messages from test_must_fail, could we go in the same
direction, and send them to descriptor 4 rather than 2? We've already
staked out descriptor 4 as something magical that must be left alone
(see 9be795fb). If we can rely on that, then it becomes a convenient way
for functions to make sure their output is going to the script's stderr.
-Peff
