Declare and assign separately to avoid masking of return values DOK-SC2155

Bad Practice:

In case of export, the return value of mycmd is ignored, and export will always return true. This may prevent conditionals, set -e and traps from working correctly.

export foo="$(mycmd)"

Recommended

Hence, when by performing export and assignment separately, the return value of the assignment will be that of mycmd. This avoids the problem.

foo="$(mycmd)"
export foo

Exceptions: If you intend to ignore the return value of an assignment, you can either ignore this warning or use:

foo=$(mycmd) || true
export foo

There is no warning for export foo=bar because bar is a literal and not a command substitution with an independent return value. It also does not warn about local -r foo=$(cmd), where declaration and assignment must be in the same command.

Bad Practice:

Similarly in case of local,

local foo="$(mycmd)"

Recommended

local foo
foo=$(mycmd)

The exit status of the command is overridden by the exit status of the creation of the local variable. For example:

$ f() { local foo=$(false) || echo foo; }; f
$ f() { local foo; foo=$(false) || echo foo; }; f
foo

Bad Practice:

Also in case of readonly,

readonly foo="$(mycmd)"

Recommended

foo="$(mycmd)"
readonly foo