Unhelpful error message when using incorrect directive key (WAS: "Expected '=' after directive key" but '=' is present (SC1072, SC1073, SC1134))

[shelvacu]

When specifying disable=foo (or any invalid value), shellcheck says Expected '=' after directive key which is very confusing since '=' is present and after the directive key.

For bugs with existing features

• Rule Id (if any, e.g. SC1000): SC1072, SC1073, SC1134 (only kindof relevant)
• My shellcheck version (shellcheck --version or "online"): Tried on both 0.11.0 and master as of 2026-03-22 (cd41f79)
• The rules' wiki pages do not already cover this
• I tried on https://www.shellcheck.net/ and verified that this is still a problem on the latest commit

Here's a snippet that shows the problem & Here's what shellcheck currently says:

When in # shellcheck directive:

$ shellcheck -s sh <(echo '# shellcheck disable=foo')

In /dev/fd/63 line 1:
# shellcheck disable=foo
^-- SC1073 (error): Couldn't parse this shellcheck directive. Fix to allow more checks.
                        ^-- SC1072 (error): Expected '=' after directive key. Fix any mentioned problems and try again.

For more information:
  https://www.shellcheck.net/wiki/SC1072 -- Expected '=' after directive key....
  https://www.shellcheck.net/wiki/SC1073 -- Couldn't parse this shellcheck di...

When in shellcheckrc:

$ shellcheck -s sh --rcfile <(echo 'disable=foo') /dev/null

In /dev/null line 1:

^-- SC1134 (error): Failed to process /dev/fd/63, line 1: Expected '=' after directive key. Fix any mentioned problems and try again.

For more information:
  https://www.shellcheck.net/wiki/SC1134 -- Failed to process /dev/fd/63, lin...

Here's what I wanted or expected to see:

Ideal: "foo-bar" is not a valid value for the "disable" directive, must be "all" or in the format SCxxxx, where xxxx is a shellcheck error code like 2086

Also good: "foo-bar" is not a valid value for the "disable" directive, or even just invalid directive