Is there a linter for fish like there is for bash with shellcheck?

Question

For sh/bash/zsh there is https://github.com/koalaman/shellcheck however there won't be support for fish with it https://github.com/koalaman/shellcheck/issues/209 - is there any linters for fish?

Answer 1

To my knowledge, there is not (and obviously this is impossible to prove).

And if someone were to create such a thing, there'd need to be consensus about what the "typical beginner's syntax issues" and "semantic problems that cause a shell to behave strangely and counter-intuitively" are.

Fish doesn't have many of POSIX sh's warts (as it was written as a reaction to them). Some examples from the shellcheck README:

echo $1                           # Unquoted variables

Fish's quoting behavior is quite different - in particular, there is no word splitting on variables, so unquoted variables usually do what you want.

v='--verbose="true"'; cmd $v      # Literal quotes in variables

This is presumably an (unsuccessful) attempt to defeat word splitting, which isn't necessary.

This example nicely illustrates the issue - there are multiple decades worth of sh scripts. The flaws and unintuitive behaviors are really well known. So well known in fact, that the common-but-incorrect workarounds are known as well. That's just not the case for fish.

(Obviously, other examples do apply to fish as well, especially the "Frequently misused commands" section.)

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Some things in fish that I know new users often trip over:

• Unquoted variables expand to one argument per element in the list (since every variable is one). That includes zero if the list is empty, which is an issue with test - e.g. test -n $var will return 0 because fish's test builtin is one of the few parts that are POSIX-compatible (since POSIX demands test with one argument returns 0). Double-quote if you always need one argument.

• {} expands to nothing and {x} expands to "x", which means find -exec needs quoting, as do some git commit-ishes (HEAD@{4}). (edit: This has since been changed, {} expands to {} and {x} expands to {x} unless x has a comma or other expansion, so HEAD@{4} works)