[package outputs] generate selected output in flake

Author: savil

internal/devpkg/narinfo_cache.go

@@ -27,6 +27,10 @@ func (p *Package) IsInBinaryCache() (bool, error) {
 	if p.PatchGlibc {
 		return false, nil
 	}
+	// Packages with non-default outputs are not used to be taken from the binary cache.
+	if len(p.Outputs) > 0 {
+		return false, nil
+	}
 	if eligible, err := p.isEligibleForBinaryCache(); err != nil {
 		return false, err
 	} else if !eligible {

internal/devpkg/package.go

@@ -78,6 +78,10 @@ type Package struct {
 	//    example: github:nixos/nixpkgs/5233fd2ba76a3accb5aaa999c00509a11fd0793c#hello
 	Raw string
 
+	// Outputs is a list of outputs to build from the package's derivation.
+	// If empty, the default output is used.
+	Outputs []string
+
 	// PatchGlibc applies a function to the package's derivation that
 	// patches any ELF binaries to use the latest version of nixpkgs#glibc.
 	PatchGlibc bool
@@ -113,6 +117,7 @@ func PackagesFromConfig(config *devconfig.Config, l lock.Locker) []*Package {
 		pkg := newPackage(cfgPkg.VersionedName(), cfgPkg.IsEnabledOnPlatform(), l)
 		pkg.DisablePlugin = cfgPkg.DisablePlugin
 		pkg.PatchGlibc = cfgPkg.PatchGlibc && nix.SystemIsLinux()
+		pkg.Outputs = cfgPkg.Outputs
 		result = append(result, pkg)
 	}
 	return result
@@ -126,6 +131,7 @@ func PackageFromStringWithOptions(raw string, locker lock.Locker, opts devopt.Ad
 	pkg := PackageFromStringWithDefaults(raw, locker)
 	pkg.DisablePlugin = opts.DisablePlugin
 	pkg.PatchGlibc = opts.PatchGlibc
+	pkg.Outputs = opts.Outputs
 	return pkg
 }
 

internal/shellgen/flake_input.go

@@ -50,9 +50,48 @@ func (f *flakeInput) PkgImportName() string {
 	return f.Name + "-pkgs"
 }
 
+type SymlinkJoin struct {
+	Name  string
+	Paths []string
+}
+
+// BuildInputsForSymlinkJoin returns a list of SymlinkJoin objects that can be used
+// as the buildInput. Used for packages that have non-default outputs that needs to
+// be combined into a single buildInput.
+func (f *flakeInput) BuildInputsForSymlinkJoin() ([]*SymlinkJoin, error) {
+	joins := []*SymlinkJoin{}
+	for _, pkg := range f.Packages {
+		// skip packages that have no non-default outputs
+		if len(pkg.Outputs) == 0 {
+			continue
+		}
+
+		attributePath, err := pkg.FullPackageAttributePath()
+		if err != nil {
+			return nil, err
+		}
+		joins = append(joins, &SymlinkJoin{
+			Name: pkg.String() + "-combined",
+			Paths: lo.Map(pkg.Outputs, func(output string, _ int) string {
+				// TODO: handle !f.IsNixpkgs() case
+				parts := strings.Split(attributePath, ".")
+				return f.PkgImportName() + "." + strings.Join(parts[2:], ".") + "." + output
+			}),
+		})
+	}
+	return joins, nil
+}
+
 func (f *flakeInput) BuildInputs() ([]string, error) {
 	var err error
-	attributePaths := lo.Map(f.Packages, func(pkg *devpkg.Package, _ int) string {
+
+	// Filter out packages that have non-default outputs
+	// These are handled in BuildInputsForSymlinkJoin
+	packages := lo.Filter(f.Packages, func(pkg *devpkg.Package, _ int) bool {
+		return len(pkg.Outputs) == 0
+	})
+
+	attributePaths := lo.Map(packages, func(pkg *devpkg.Package, _ int) string {
 		attributePath, attributePathErr := pkg.FullPackageAttributePath()
 		if attributePathErr != nil {
 			err = attributePathErr

internal/shellgen/generate.go

@@ -30,7 +30,7 @@ var tmplFS embed.FS
 // devbox.PrintEnv, which is the core function from which devbox shell/run/direnv
 // functionality is derived.
 func GenerateForPrintEnv(ctx context.Context, devbox devboxer) error {
-	defer trace.StartRegion(ctx, "generateShellFiles").End()
+	defer trace.StartRegion(ctx, "generateForPrintEnv").End()
 
 	plan, err := newFlakePlan(ctx, devbox)
 	if err != nil {

internal/shellgen/tmpl/flake_remove_nixpkgs.nix.tmpl

@@ -46,7 +46,17 @@
             })
             {{- end }}
             {{- end }}
-            {{- range .FlakeInputs }}
+            {{- range $_, $flakeInput := .FlakeInputs }}
+            {{- range .BuildInputsForSymlinkJoin }}
+            (pkgs.symlinkJoin {
+              name = "{{.Name}}";
+              paths = [
+                {{- range .Paths }}
+                {{.}}
+                {{- end }}
+              ];
+            })
+            {{- end }}
             {{- range .BuildInputs }}
             {{.}}
             {{- end }}