From 827232d6dd2b7787749afdfef614fbea8d88ebe9 Mon Sep 17 00:00:00 2001 From: Silvan Mosberger Date: Mon, 20 Nov 2023 17:55:53 +0100 Subject: [PATCH] lib.fileset: Document decision for strict existence checks Co-authored-by: Robert Hensing --- lib/fileset/README.md | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/lib/fileset/README.md b/lib/fileset/README.md index f44df6fffeca..93e0199c32a4 100644 --- a/lib/fileset/README.md +++ b/lib/fileset/README.md @@ -252,3 +252,16 @@ The `fileFilter` function takes a path, and not a file set, as its second argume - (+) That can change depending on which files are included, so if it's used for `fileFilter` it would change the `subpath`/`components` value depending on which files are included. - (+) If necessary, this restriction can be relaxed later, the opposite wouldn't be possible + +### Strict path existence checking + +Coercing paths that don't exist to file sets always gives an error. + +- (-) Sometimes you want to remove a file that may not always exist using `difference ./. ./does-not-exist`, + but this does not work because coercion of `./does-not-exist` fails, + even though its existence would have no influence on the result. + - (+) This is dangerous, because you wouldn't be protected against typos anymore. + E.g. when trying to prevent `./secret` from being imported, a typo like `difference ./. ./sercet` would import it regardless. + - (+) `difference ./. (maybeMissing ./does-not-exist)` can be used to do this more explicitly. + - (+) `difference ./. (difference ./foo ./foo/bar)` should report an error when `./foo/bar` does not exist ("double negation"). Unfortunately, the current internal representation does not lend itself to a behavior where both `difference x ./does-not-exists` and double negation are handled and checked correctly. + This could be fixed, but would require significant changes to the internal representation that are not worth the effort and the risk of introducing implicit behavior.