Overriding squirrel-sql source not working for me

[waffle8946]

@racingmars

Okay, so I can’t reference ${src} like the original package does, even though it’s defined right there in the same block?

Yes, because the original expression uses rec, and yours does not.
See https://nix.dev/manual/nix/2.24/language/syntax#recursive-sets

@racingmars

(However, if I put in the wrong sha256 hash, I do get a hash mismatch error, so it does appear to be downloading my alternate zip archive even thought it’s not unzipping it.)

You will have to override unpackPhase as well, because they use rec instead of the finalAttrs pattern. See https://nixos.org/manual/nixpkgs/unstable/#mkderivation-recursive-attributes for more context.