Re: [PATCH] tests: turn on test-lint-shell-syntax by default

Torsten Bögershausen <tboegi@web.de> writes:

I think everybody involved in this discussion already knows that; the point is that it can easily give false negative, without the scripts working very hard to do so.

If we did not care about incurring runtime performance cost, we could arrange:

 - the test framework to define a variable $TEST_ABORT that has a
   full path to a file that is in somewhere test authors cannot
   touch unless they really try hard to (i.e. preferrably outside
   $TRASH_DIRECTORY, as it is not uncommon for to tests to do "rm *"
   there). This location should be per $(basename "$0" .sh) to allow
   running multiple tests in paralell;

 - the test framework to "rm -f $TEST_ABORT" at the beginning of
   test_expect_success/failure;

 - test_expect_success/failure to check $TEST_ABORT and if it
   exists, abort the execution, showing the contents of the file as
   an error message.

Then you can wrap commands whose use we want to limit, perhaps like this, in the test framework:

	which () {
		cat >"$TEST_ABORT" <<-\EOF
		Do not use unportable 'which' in the test script.
                "if type $cmd" is a good way to see if $cmd exists.
		EOF
	}

	sed () {
		saw_wantarg= must_abort=
                for arg
                do
			if test -n "$saw_wantarg"
                        then
				saw_wantarg=
                                continue
			fi
			case "$arg" in
			--)	break ;; # end of options
			-i)	echo >"$TEST_ABORT" "Do not use 'sed -i'"
				must_abort=yes
				break ;;
                        -e)	saw_wantarg=yes ;; # skip next arg
			-*)	continue ;; # options without arg
			*)	break ;; # filename
			esac
		done
		if test -z "$must_abort"
			sed "$@"
		fi
	}

Then you can check that TEST_ABORT does not appear in test scripts (ensuring that they do not attempt to circumvent the mechanis) and catch use of unwanted commands or unwanted extended features of commands at runtime.

But this will incur runtime performace hit, so I am not sure it would be worth it.