[bug] Fix parseStorePathFromInstallableOutput (#2098)

## Summary

Fix regression introduced in
#2076

I misunderstood the API. A null value (in modern API) or a valid: false
(in legacy API) occur when store path doesn't exist. Whether the store
path itself is a valid store path doesn't matter, obviously if it is not
a valid path, it won't be present in the store, but if it's valid and
not installed, it will return null value or valid: false. The users of
this function do not want to ignore these paths.

Edit: This bug is a bit less bad than initially thought. Because we
install non-cached packages in flake, so anything missing would be
installed then.

## How was it tested?

Unit test. 

This is tricky to test. I added a test script that can hopefully catch
this.

Edit: This test doesn't actually catch this because the package ends up
getting installed later on (in the flake). I still think this test is
good to have.

Author: mikeland73

internal/nix/store.go

@@ -87,22 +87,17 @@ func StorePathsAreInStore(ctx context.Context, storePaths []string) (map[string]
 
 // Older nix versions (like 2.17) are an array of objects that contain path and valid fields
 type pathInfoLegacy struct {
-	Path  string `json:"path"`
-	Valid bool   `json:"valid"`
+	Path string `json:"path"`
 }
 
 // parseStorePathFromInstallableOutput parses the output of `nix store path-from-installable --json`
 // This function is decomposed out of StorePathFromInstallable to make it testable.
 func parseStorePathFromInstallableOutput(output []byte) (map[string]any, error) {
 	// Newer nix versions (like 2.20) have output of the form
 	// {"<store-path>": {}}
-	// if a store path is used as an installable, the keys will be present even if invalid but
-	// the values will be null.
+	// Note that values will be null if paths are not in store.
 	var out1 map[string]any
 	if err := json.Unmarshal(output, &out1); err == nil {
-		maps.DeleteFunc(out1, func(k string, v any) bool {
-			return v == nil
-		})
 		return out1, nil
 	}
 
@@ -111,9 +106,7 @@ func parseStorePathFromInstallableOutput(output []byte) (map[string]any, error)
 	if err := json.Unmarshal(output, &out2); err == nil {
 		res := map[string]any{}
 		for _, outValue := range out2 {
-			if outValue.Valid {
-				res[outValue.Path] = true
-			}
+			res[outValue.Path] = true
 		}
 		return res, nil
 	}

internal/nix/store_test.go

@@ -21,7 +21,7 @@ func TestParseStorePathFromInstallableOutput(t *testing.T) {
 		},
 		{
 			name:     "go-basic-nix-2-17-0",
-			input:    `[{"path":"/nix/store/fgkl3qk8p5hnd07b0dhzfky3ys5gxjmq-go-1.22.0","valid":true}]`,
+			input:    `[{"path":"/nix/store/fgkl3qk8p5hnd07b0dhzfky3ys5gxjmq-go-1.22.0"}]`,
 			expected: []string{"/nix/store/fgkl3qk8p5hnd07b0dhzfky3ys5gxjmq-go-1.22.0"},
 		},
 	}

testscripts/lockfile/nopaths.txt

@@ -0,0 +1,23 @@
+# Test installing a package without outputs in the store path. 
+# NOTE: Purposefully using a weird version to ensure it is not already in store.
+
+exec devbox run curl --version | grep -o 'curl\s7\.87\.0'
+stdout 'curl 7.87.0'
+
+-- devbox.json --
+{
+  "packages": ["[email protected]"],
+}
+
+-- devbox.lock --
+{
+  "lockfile_version": "1",
+  "packages": {
+    "[email protected]": {
+      "last_modified": "2023-02-26T03:47:33Z",
+      "resolved": "github:NixOS/nixpkgs/9952d6bc395f5841262b006fbace8dd7e143b634#curl",
+      "source": "devbox-search",
+      "version": "7.87.0"
+    }
+  }
+}