ShellCheck directives are only valid in front of complete compound commands, like if, not e.g. individual elif branches.

Problematic code:

if [ "$prod" = "true" ]
then
  echo "Prod mode"
# shellcheck disable=2154
elif [ "$debug" = "true" ]
then
  echo "Debug mode"
fi

Correct code:

# Applies to entire `if...fi` command
# shellcheck disable=2154
if [ "$prod" = "true" ]
then
  echo "Prod mode"
elif [ "$debug" = "true" ]
then
  echo "Debug mode"
fi

or

if [ "$prod" = "true" ]
then
  echo "Prod mode"
elif  # Applies only to this [ .. ] command
      # shellcheck disable=2154
      [ "$debug" = "true" ]
then
  echo "Debug mode"
fi

Rationale:

You appear to have put a directive before a non-command keyword, such as elif, else, do, ;; or similar.

Unlike many other linters, ShellCheck comment directives apply to the next shell command, rather than to the next line of text.

This means that you can put a directive in front of a while loop, if statement or function definition, and it will apply to that entire structure.

However, it also means that you can not apply the directive to non-commands like an individual elif or else block since these are not commands by themselves, and rather just parts of an if compound command.

Please move the directive in front of the nearest applicable command that contains the code you want to apply it to, such as before the if.

Exceptions:

None.