mkDummySrc: fix cleaning to work with Nix store overrides (#448)

* Turns out if a build is invoked with `--store` then the source
  cleaning filter will observe paths rooted at the alternative store
  which breaks out previous string handling (and results in incorrectly
  ignoring files which should be included)

.gitignore

@@ -1,4 +1,5 @@
 gcroot
 result*
 target/
+/extra-tests/*/alt-store
 /extra-tests/*/flake.lock

CHANGELOG.md

@@ -22,6 +22,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 * All dependencies (outside of `nixpkgs`) have been dropped from the (main)
   flake.lock file so they do not pollute downstream projects' lock files.
 
+### Fixed
+* `mkDummySrc` now properly handles file cleaning (and file including) when a
+  build is invoked with a `--store ...` override
+
 ## [0.14.3] - 2023-10-17
 
 ### Changed

extra-tests/alt-store/flake.nix

@@ -0,0 +1,18 @@
+{
+  inputs = {
+    crane.url = "github:ipetkov/crane";
+    nixpkgs.follows = "crane/nixpkgs";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { flake-utils, crane, ... }: flake-utils.lib.eachDefaultSystem (system:
+    let
+      craneLib = crane.lib.${system};
+    in
+    {
+      # https://github.com/ipetkov/crane/issues/446
+      packages.default = craneLib.buildPackage {
+        src = craneLib.cleanCargoSource (craneLib.path ../../checks/simple);
+      };
+    });
+}

extra-tests/alt-store/test.sh

@@ -0,0 +1,8 @@
+#!/bin/sh
+# Regression test for https://github.com/ipetkov/crane/issues/446
+set -eu
+
+scriptDir=$(dirname "$0")
+cd "${scriptDir}"
+
+nix build .#default --override-input crane ../.. --store $(pwd)/alt-store

extra-tests/test.sh

@@ -18,6 +18,7 @@ runTest() {
 scriptPath=$(dirname "$0")
 cd "${scriptPath}"
 
+runTest ./alt-store/test.sh
 runTest ./dummy-does-not-depend-on-flake-source-via-path/test.sh
 runTest ./dummy-does-not-depend-on-flake-source-via-self/test.sh
 runTest ./fetch-cargo-git/test.sh

lib/mkDummySrc.nix

@@ -93,7 +93,7 @@ let
     then src.origSrc
     else src;
 
-  uncleanSrcBasePath = (toString origSrc) + "/";
+  uncleanSrcBasePath = builtins.unsafeDiscardStringContext ((toString origSrc) + "/");
   uncleanFiles = findCargoFiles origSrc;
 
   cargoTomlsBase = uncleanSrcBasePath;
@@ -112,7 +112,11 @@ let
       name = "cleaned-mkDummySrc";
       filter = path: type:
         let
-          strippedPath = removePrefix uncleanSrcBasePath path;
+          # using `path` can have weird consequences here with alternative store paths
+          # so we cannot assume `uncleanSrcBasePath` will be a strict prefix. Thus we
+          # chop off anything up to and including its value
+          # https://github.com/ipetkov/crane/issues/446
+          strippedPath = lib.last (lib.splitString uncleanSrcBasePath path);
           filter = x:
             if type == "directory" then
               lib.hasPrefix strippedPath x