nix_completer: Add action for completing attributes on flakes

completers/nix_completer/cmd/action/flake.go

@@ -0,0 +1,105 @@
+package action
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"slices"
+	"strings"
+
+	"github.com/carapace-sh/carapace"
+	"github.com/carapace-sh/carapace-bin/pkg/actions/tools/nix"
+)
+
+// ActionFlakeRefs completes a full flake reference
+// It will only complete attributes for local flakes or flakes
+// in the flake registry.
+// It takes in the subcommand being completed
+//
+// nixpkgs#hello
+// .#foo
+func ActionFlakeRefs(fullCmd []string) carapace.Action {
+	return carapace.ActionMultiPartsN("#", 2, func(c carapace.Context) carapace.Action {
+		switch len(c.Parts) {
+		case 0:
+			return nix.ActionFlakes().Suffix("#")
+		default:
+			return ActionFlakeAttributes(fullCmd, c.Parts[0], c.Value)
+		}
+	})
+}
+
+// ActionFlakeAttributes completes attributes on a flake
+// Completions are only supplied for local flakes or flakes
+// in the registry.
+//
+// hello
+// packages.x86_64-linux.hello
+func ActionFlakeAttributes(fullCmd []string, flake, flakePath string) carapace.Action {
+	return carapace.ActionCallback(func(c carapace.Context) carapace.Action {
+		// Get completions from the flake registry
+		c.Setenv("NIX_GET_COMPLETIONS", fmt.Sprint(len(fullCmd)))
+		completionArgs := append(fullCmd[1:], flake)
+
+		var stdout, stderr bytes.Buffer
+		cmd := c.Command("nix", completionArgs...)
+		cmd.Stdout = &stdout
+		cmd.Stderr = &stderr
+
+		if err := cmd.Run(); err != nil {
+			return carapace.ActionValues()
+		}
+
+		// Check if the given flake is in the registry or is a local path
+		// For some reason, nix adds \b to completion items
+		rawLines := strings.ReplaceAll(stdout.String(), "\r\b", "")
+		lines := strings.Split(rawLines, "\n")
+
+		flakeInRegistry := slices.ContainsFunc(lines[1:], func(s string) bool {
+			return strings.Trim(s, " \t") == flake
+		})
+		flakeIsLocal := directoryExists(flake)
+
+		if !flakeInRegistry && !flakeIsLocal {
+			return carapace.ActionValues()
+		}
+
+		// Get completions using the nix cli
+		stdout.Reset()
+		stderr.Reset()
+
+		completionArgs = append(fullCmd[1:], flake+"#"+flakePath)
+		cmd = c.Command("nix", completionArgs...)
+		cmd.Stdout = &stdout
+		cmd.Stderr = &stderr
+
+		if err := cmd.Run(); err != nil {
+			return carapace.ActionValues()
+		}
+
+		// Remove \r for consistency with line endings
+		// For some reason, nix adds \b to completion items
+		rawLines = strings.ReplaceAll(stdout.String(), "\r\b", "")
+		lines = strings.Split(rawLines, "\n")
+
+		// The first line is always "attrs"
+		completionResults := lines[1:]
+
+		// Remove the flake# prefix
+		for i := range completionResults {
+			completionResults[i] = strings.Trim(completionResults[i], " \t")
+			completionResults[i] = strings.TrimPrefix(completionResults[i], flake+"#")
+		}
+
+		return carapace.ActionValues(completionResults...)
+	})
+}
+
+func directoryExists(path string) bool {
+	info, err := os.Stat(path)
+	if err != nil {
+		return false
+	}
+
+	return info.IsDir()
+}

completers/nix_completer/cmd/build.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"github.com/carapace-sh/carapace"
+	"github.com/carapace-sh/carapace-bin/completers/nix_completer/cmd/action"
 	"github.com/carapace-sh/carapace-bin/pkg/actions/tools/nix"
 	"github.com/spf13/cobra"
 )
@@ -39,5 +40,5 @@ func init() {
 		"profile":             carapace.ActionFiles(),
 		"reference-lock-file": carapace.ActionFiles("lock"),
 	})
-	carapace.Gen(buildCmd).PositionalCompletion(nix.ActionFlakes())
+	carapace.Gen(buildCmd).PositionalCompletion(action.ActionFlakeRefs([]string{"nix", "build"}))
 }

completers/nix_completer/cmd/develop.go

@@ -2,6 +2,7 @@ package cmd
 
 import (
 	"github.com/carapace-sh/carapace"
+	"github.com/carapace-sh/carapace-bin/completers/nix_completer/cmd/action"
 	"github.com/carapace-sh/carapace-bin/pkg/actions/os"
 	"github.com/carapace-sh/carapace-bin/pkg/actions/tools/nix"
 	"github.com/spf13/cobra"
@@ -50,5 +51,5 @@ func init() {
 		"reference-lock-file": carapace.ActionFiles("lock"),
 		"unset":               os.ActionEnvironmentVariables(),
 	})
-	carapace.Gen(developCmd).PositionalCompletion(nix.ActionDevShells())
+	carapace.Gen(developCmd).PositionalCompletion(action.ActionFlakeRefs([]string{"nix", "develop"}))
 }

pkg/actions/tools/nix/flake.go

@@ -30,7 +30,7 @@ func ActionFlakes() carapace.Action {
 			carapace.ActionDirectories(),
 			carapace.ActionStyledValuesDescribed(vals...),
 		).ToA()
-	}).Cache(time.Minute).Suffix("#")
+	}).Cache(time.Minute)
 }
 
 func styleForRegistry(s string) string {