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Updated SC2293 (markdown)
38
SC2293.md
38
SC2293.md
@@ -1,49 +1,29 @@
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## bats: ! \<command> will never fail the test
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## When eval'ing @Q-quoted words, use * rather than @ as the index.
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### Problematic code:
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```sh
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#!/usr/bin/env bats
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@test "test" {
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# ... code
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! test_file_exists
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# ... more code
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}
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eval "$MYCOMMAND ${@@Q}"
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```
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### Correct code:
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```sh
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#!/usr/bin/env bats
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@test "test" {
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# ... code
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run ! test_file_exists
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# ... more code
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}
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eval "$MYCOMMAND ${*@Q}"
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```
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### Rationale:
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Bats uses `set -e` and `trap ERR` to catch test failures as early as possible.
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Although the return code of a `!` negated command is inverted, they will never trigger `errexit`, due to a bash design decision (see [Related Resources](#related-resources)).
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This means that tests which use `!` can never fail.
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ShellCheck noticed that you are calling `eval` and including an escaped array. However, the array is passed as multiple arguments and relies on being implicitly joined together to form a single shell string, which `eval` can then evaluate.
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Starting with bats 1.5.0 you can use `!` inside `run`.
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If you are still using an older bats version, you can rewrite `! <command>` to `<command> && exit 1`.
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Instead, prefer building your shell string with explicit string concatenation by using `*` instead of `@` for the index, such as `${*@Q}` or `${array[*]@Q}`.
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This suggestion is equivalent to [[SC2124]], but for `eval` arguments rather than string variables.
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### Exceptions:
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The return code of the last command in the test will be the exit code of the test function.
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This means that you can use `! <command>` on the last line of the test and it will still fail appropriately.
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However, you are encouraged to still use `run !` in this case for consistency.
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Shellcheck won't emit this error when using `! <command>` as last command in a test to avoid confusing users whose tests work as intended.
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None.
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### Related resources:
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* [SC2251: This ! is not on a condition and skips errexit](SC2251.md)
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* [Stackoverflow: Why do I need parenthesis In bash `set -e` and negated return code](https://stackoverflow.com/a/39582012/760746)
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* [bash manpage](https://linux.die.net/man/1/bash) (look at `trap [-lp] [[arg] sigspec ...]`):
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> The ERR trap is not executed [...] if the command's return value is being inverted via !
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* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!
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