nu-inline-diagnostics

Fork of Nushell that shows LSP diagnostics inline in the REPL as you type. It ships a generic LSP client (in a forked reedline), so it is the opposite of the built-in nu --lsp server: instead of serving diagnostics, it consumes them from any language server and renders them under your input. Intended for use with nu-lint but works with any LSP server.

The installed binary is still called nu. nu-inline-diagnostics is only the package/flake name.

Disclaimer: This fork was made to make it easier for people to experiment with inline diagnostics in the terminal for Nushell. As far as I know this is not too common yet. For the most-up-to date mainline Nushell features and development, please refer to the original repository. Otherwise, go ahead and play around with this fork.

Features:

• Multiple underlined spans
• Inline hints under spans
• Colors for warning / info / error level
• Automatic fixes (for most rules)
• User / workspace ignore action (for noisy rules)

Screenshot of inline diagnostics with multiple labels:

Screenshot of the code action menu being active and suggesting fixes:

Architecture

flowchart LR
    subgraph Terminal
        Nu[nu binary]
        Reedline[reedline fork]
    end
    subgraph LSP Server
        NuLint[nu-lint]
    end

    Nu -->|line editing| Reedline
    Reedline <-->|LSP protocol| NuLint
    NuLint -->|diagnostics, fixes| Reedline

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The forked reedline adds an LSP client that communicates with one or more language servers configured via $env.REEDLINE_LSP_SERVERS (see Usage). Each server analyzes your input and returns diagnostics and code actions that are displayed inline.

Installation

Install a language protocol server (LSP server). I recommend nu-lint:

cargo install nu-lint

Build the main binary nu with a Rust compiler toolchain:

• For Nix users: nix run . (or add this repo's flake to your system dependencies)
• Otherwise, if you are on a more mainstream machine, install rustup and:

cargo install --git https://github.com/wvhulle/nushell

Keep in mind this will overwrite any other nu binary you have there (such as the official one).

Usage

Configure one or more language servers with $env.REEDLINE_LSP_SERVERS, a list of records. Each record takes a command (required) plus optional language_id (default nushell) and uri_scheme (default file):

$env.REEDLINE_LSP_SERVERS = [
    { command: "nu-lint --lsp", language_id: "nushell", uri_scheme: "repl" }
    # Add more servers here; diagnostics from all of them are shown inline.
]

Two fields drive how a server sees your input:

• language_id picks the file extension the input is presented as, so the server treats it as the right language: nushell → .nu, bash → .sh, rust → .rs, python → .py, and so on.
• uri_scheme picks the document URI:
  • "file" (default) presents the input as a real file ./.reedline-repl.<ext> in the current directory. Use this for servers that resolve project config by path, such as ast-grep (it needs to find sgconfig.yml).
  • "repl" presents it as repl:///repl.<ext>. Use this for servers that filter out REPL-inappropriate actions, such as nu-lint.

Examples

nu-lint linting your Nushell input (run from anywhere):

$env.REEDLINE_LSP_SERVERS = [
    { command: "nu-lint --lsp", language_id: "nushell", uri_scheme: "repl" }
]

ast-grep with a rule set — run nu from inside the ast-grep project so sgconfig.yml resolves. Match language_id to the rules' language: field, e.g. bash rules (ast-grep-git-to-jj):

$env.REEDLINE_LSP_SERVERS = [
    { command: "ast-grep lsp", language_id: "bash", uri_scheme: "file" }
]

...or Rust rules (ast-grep-intro):

$env.REEDLINE_LSP_SERVERS = [
    { command: "ast-grep lsp", language_id: "rust", uri_scheme: "file" }
]

Single-server shorthand

For one server you can use the simpler environment variables instead (a fallback used only when REEDLINE_LSP_SERVERS is unset). For nu-lint:

$env.REEDLINE_LS = "nu-lint --lsp"
$env.REEDLINE_LS_LANG = "nushell"   # default: nushell
$env.REEDLINE_LS_SCHEME = "repl"    # default: file

Run the shell: ~/.cargo/bin/nu (or add to your path)

Key bindings:

• Open fix/ignore menu when a violation is detected with ctrl+..
• Navigate between fixes and ignore actions: tab
• Apply fix directly in the prompt: enter

You can file issues related to incorrect lints and fixes at nu-lint.