Bash shell options for errors

[adthrasher]

We often use some variation of set -euo pipefail in our task declarations. It would be helpful to have a lint rule to catch if this is forgotten.

For completeness here is the BASH man page for set.

-e
Exit immediately if a pipeline (see Pipelines), which may consist of a single simple command (see Simple Commands), a list (see Lists of Commands), or a compound command (see Compound Commands) returns a non-zero status. The shell does not exit if the command that fails is part of the command list immediately following a while or until keyword, part of the test in an if statement, part of any command executed in a && or || list except the command following the final && or ||, any command in a pipeline but the last, or if the command’s return status is being inverted with !. If a compound command other than a subshell returns a non-zero status because a command failed while -e was being ignored, the shell does not exit. A trap on ERR, if set, is executed before the shell exits.

This option applies to the shell environment and each subshell environment separately (see Command Execution Environment), and may cause subshells to exit before executing all the commands in the subshell.

If a compound command or shell function executes in a context where -e is being ignored, none of the commands executed within the compound command or function body will be affected by the -e setting, even if -e is set and a command returns a failure status. If a compound command or shell function sets -e while executing in a context where -e is ignored, that setting will not have any effect until the compound command or the command containing the function call completes.

-o option-name
Set the option corresponding to option-name:
pipefail
If set, the return value of a pipeline is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands in the pipeline exit successfully. This option is disabled by default.

-u
Treat unset variables and parameters other than the special parameters ‘@’ or ‘’, or array variables subscripted with ‘@’ or ‘’, as an error when performing parameter expansion. An error message will be written to the standard error, and a non-interactive shell will exit.

[a-frantz]

Many WDL tasks are single (pipeless) commands. We should not warn about a missing set -euo pipefail in those cases. That means we can't just blindly check that the string is present in the beginning of a command block, we will have to do some actual Bash parsing. That strikes me as something we want to avoid. I don't want to parse Bash.

I think this can tie into a future shellcheck call. I have not gone through the shellcheck docs, but they may have a warning that accomplishes the above more robustly than any implementation from us. If not, I'm sure someone has wanted this lint before and we can find a solution off the shelf somewhere.

Basically, I think this is a lint we outsource as opposed to writing our own. But I have not searched yet to see whether there's tooling available for us.