nixd v2.9.0: Intelligent Refactoring

Welcome to nixd 2.9.0! This release features an extensive suite of Code Actions contributed by @takeokunn, greatly enhancing flexibility when working with Nix expressions. We have also optimized documentation support and performance details.

🌟 Highlights

🛠️ Powerful Code Refactoring (Code Actions)

Nix can sometimes feel verbose. This update introduces a series of "one-click refactors" to keep your code clean:

AttrSet Restructuring

• Flatten & Pack: Quickly convert between nested sets and dotted paths (#757, #758). nix { foo = { bar = 1; }; } # <-> { foo.bar = 1; }
• The "Pack" Series: Added Pack One, Shallow Pack All, and Recursive Pack All to easily reorganize complex attribute definitions (#759).
  • Pack One: Transforms a single dotted binding into a nested set.
    • { foo.bar = 1; } → { foo = { bar = 1; }; }
  • Shallow Pack All: When siblings share a prefix, packs the first level but preserves remaining dots.
    • { foo.bar.x = 1; foo.baz = 2; } → { foo = { bar.x = 1; baz = 2; }; }
  • Recursive Pack All: Fully nests all sibling bindings recursively.
    • { foo.bar.x = 1; foo.baz = 2; } → { foo = { bar = { x = 1; }; baz = 2; }; }

Syntax Transformations

• Inherit Conversion: Convert explicit bindings to inherit syntax, or expand them back (#770, #773). ```nix # Pattern: Simple variable assignment { foo = foo; bar = bar; } -> { inherit foo bar; }

  Pattern: Select from source

  { x = lib.x; y = lib.y; } -> { inherit (lib) x y; } ```

• Eliminate with: Provides actions to refactor with statements into safer let/inherit bindings (#768). nix # Before with lib; optionalString true "yes" # After let inherit (lib) optionalString; in optionalString true "yes"

• Strings & Quotes: Support for adding/removing quotes from attribute names (#756) and string literal syntax conversion (#775).

Developer Productivity

• JSON to Nix: Convert selected JSON snippets to Nix format instantly (#763).

  :::nix {"foo": 1, "bar": true, "nested": {"key": "value"}}

  →

  { foo = 1; bar = true; nested = { key = "value"; }; }

• Extract to File: Extract a selected expression and refactor it into a standalone file (#767).

Before:

:::nix
{ pkgs }: { buildInputs = [ pkgs.foo pkgs.bar ]; }

After extraction:

- New file (buildInputs.nix):
{ pkgs }:
[ pkgs.foo pkgs.bar ]
- Original file:
{ pkgs }: { buildInputs = import ./buildInputs.nix { inherit pkgs; }; }

• Auto-complete Formals: For undefined variables, use a Code Action to add them to function formals (#777).

Before	After
{x}: y	{x, y}: y
{ }: y	{ y }: y
{ ... }: y	{ y, ... }: y
{x, ...}: y	{x, y, ...}: y

• Quick Cleanup: Automatically remove unused let bindings (#779).

Before	After
let x = 1; in 2	let in 2
let x = 1; y = 2; in y	let y = 2; in y
let x = 1; y = 2; in 3	let y = 2; in 3 (each gets separate action)

📚 Documentation & Interaction

• Noogle Integration: Unsure how to use a lib function? You can now open noogle.dev documentation directly via a Code Action (#764).

• lib.optionalString → Opens https://noogle.dev/f/lib/optionalString

• lib.strings.optionalString → Opens https://noogle.dev/f/lib/strings/optionalString

• Enhanced Hover: Hovering now supports expression selection and provides more detailed documentation (#745). These descriptions are pulled directly from RFC 0145 · Doc-comments within nixpkgs.

🐞 Fixes & Improvements

• Formatting Optimization: Saving is only triggered if the formatter actually modifies the code, reducing unnecessary pop-ups (#771) - by @cubewhy.
• Semantic Fixes: Fixed incorrect diagnostics when using inherit (builtins) inside let blocks (#782). nixd now correctly handles these in let blocks while ignoring them in standard attrsets.
• Stability: Added regression tests for Hover functionality (#781).

🤝 Community

• A special welcome to our new contributor @cubewhy!
• Congratulations to @takeokunn for becoming the Code Owner for the Code Actions module in nixd.

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Full Changelog: v2.8.2...v2.9.0