In preparation for the deprecation of `stdenv.isX`.
These shorthands are not conducive to cross-compilation because they
hide the platforms.
Darwin might get cross-compilation for which the continued usage of `stdenv.isDarwin` will get in the way
One example of why this is bad and especially affects compiler packages
https://www.github.com/NixOS/nixpkgs/pull/343059
There are too many files to go through manually but a treewide should
get users thinking when they see a `hostPlatform.isX` in a place where it
doesn't make sense.
```
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv.is" "stdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenv'.is" "stdenv'.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "clangStdenv.is" "clangStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "gccStdenv.is" "gccStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "stdenvNoCC.is" "stdenvNoCC.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "inherit (stdenv) is" "inherit (stdenv.hostPlatform) is"
fd --type f "\.nix" | xargs sd --fixed-strings "buildStdenv.is" "buildStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "effectiveStdenv.is" "effectiveStdenv.hostPlatform.is"
fd --type f "\.nix" | xargs sd --fixed-strings "originalStdenv.is" "originalStdenv.hostPlatform.is"
```
This focuses on Rust packages, since the most commonly used argument
parser library (clap/structopt) makes the following pattern natural and
thus common:
postInstall = ''
installShellCompletion --cmd foo \
--bash <($out/bin/foo completion bash) \
…
This commit just guards those with
lib.optionalString (stdenv.buildPlatform.canExecute stdenv.hostPlatform)
splitting the string where unrelated actions are performed.
This is done with the following bash script:
```
#!/usr/bin/env bash
process_line() {
local filename=${1%:}
if [[ $4 =~ \"(.*)\"\; ]]; then
local sha256="${BASH_REMATCH[1]}"
fi
[[ -z $sha256 ]] && return 0
local hash=$(nix hash to-sri --type sha256 $sha256)
echo "Processing: $filename"
echo " $sha256 => $hash"
sed -i "s|cargoSha256 = \"$sha256\"|cargoHash = \"$hash\"|"
$filename
}
# split output by line
grep -r 'cargoSha256 = ' . | while IFS= read -r line; do
# split them further by space
read -r -a parts <<< "$line"
process_line "${parts[@]}"
done
```
