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Updated wording from code review

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Cody Hiar 2022-07-04 14:39:11 -06:00
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doc/builders/fetchers.chapter.md
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@ -4,7 +4,7 @@ Nixpkgs provides fetchers for different protocols and services. Fetchers are fun
## Caveats
Fetchers store their output in the nix store, or cache, using Nix's [_fixed output derivation_](https://nixos.org/manual/nix/stable/#fixed-output-drvs). Later, Nix can reuse the downloaded contents via their hash. While the caching improves performance, it can lead to some confusion. For example, consider the following fetcher:
Fetchers create [_fixed output derivations_](https://nixos.org/manual/nix/stable/#fixed-output-drvs) from downloaded files. Later, Nix can reuse the downloaded files via their hash. While the caching improves performance, it can lead to some confusion. For example, consider the following fetcher:
```nix
fetchurl {
@ -33,7 +33,7 @@ fetchurl {
Hash mismatches generate an error message containing the correct sha256.
A similar problem arises when changing a fetcher's implementation. Changes may cause a fixed output derivation to fail. Failures can go undetected if the output of the derivation already exists in the nix store or cache. The [`invalidateFetcherByDrvHash`](#tester-invalidateFetcherByDrvHash) function helps prevent this. It uses the derivation hash in the output's name to invalidate the cache.
A similar problem arises while testing changes to a fetcher's implementation. If the output of the derivation already exists in the nix store or cache, test failures can go undetected. The [`invalidateFetcherByDrvHash`](#tester-invalidateFetcherByDrvHash) function helps prevent reusing cached derivations.
## `fetchurl` and `fetchzip` {#fetchurl}