Features

Syntax highlighting for embedded languages inside Nix multi-line strings ('' ... '').

Supported activation styles, with the most automatic options first:

• automatic detection for configured function calls, such as pkgs.writeShellScript "name" ''
• automatic detection for configured variable name prefixes or suffixes, such as fooScript = ''
• comments inside the string, such as # shell or # syntax: python
• comments before the string, such as # syntax: json before an attribute assignment
• tree-sitter-compatible Nix block directives, such as /* shell */ ''

Usage

Pattern 1: Automatic detection via pkgs.writeShellScript-style calls

When a bound Nix function (e.g. writeShellScript, writeBash, writeDash) is called with a '' multiline string argument on the same line, the string content is automatically highlighted as the bound language — no marker needed:

script = pkgs.writeShellScript "my-script" ''
  echo "Hello, world!"
  ls -la
'';

Built-in bindings (all highlight as shell/bash):

The function name may be prefixed (e.g. pkgs.writeShellScript, lib.writeShellScript) or bare (after inherit). The opening '' must appear on the same line as the function call.

Pattern 2: Automatic detection via variable name prefixes or suffixes

You can configure variable name markers that imply an embedded language. For example, with this setting:

{
  "nix-embedded-languages.variableMarkers.suffix": {
    "Script": "shell"
  }
}

variables ending in Script are highlighted as shell when assigned a multiline string:

fooScript = ''
  echo "Hello, world!"
'';

Prefix markers work the same way with nix-embedded-languages.variableMarkers.prefix.

Pattern 3: Short form (inside string)

Place # lang on its own line inside the string:

script = ''
  # shell
  echo "Hello, world!"
  ls -la
'';

Pattern 4: Explicit form with # syntax: (inside string)

For clarity, use # syntax: lang:

script = ''
  # syntax: python
  def greet(name):
      print(f"Hello, {name}!")
  greet("World")
'';

Pattern 5: Typescript / C-style comment // syntax: (inside string)

For languages where // is a comment:

code = ''
  // syntax: javascript
  const greeting = "Hello!";
  console.log(greeting);
'';

Pattern 6: Double-dash comment -- syntax: (inside string)

For languages where -- is a valid comment, such as Lua and SQL:

initLua = ''
  -- syntax: lua
  function greet(name)
    print("Hello, " .. name)
  end
'';

Pattern 7: Comment before string (for JSON, etc.)

For languages without comments (like JSON), place the marker before the string as a Nix comment. This form is useful when the embedded language cannot safely carry its own syntax marker:

# syntax: json
configData = ''
  {
    "name": "example",
    "version": "1.0.0"
  }
'';

The '' string opener can appear after a simple same-line Nix declaration. The embedded highlighting stops before the closing multiline-string delimiter.

Pattern 8: Tree-sitter compatible block comment before string

You can also use the Nix block comment directive form recognized by tree-sitter:

shellCode = /* shell */ ''
  cp foo bar
'';

Built-In Languages

Extension Settings

Regex fragments in configuration keys

Custom language identifiers, function bindings, and variable markers accept only restricted regex fragments in their keys. Allowed regex operators are:

• | for alternation
• * for zero or more
• + for one or more
• ? for optional

Other regex syntax, such as groups, character classes, anchors, and ., is not accepted. If you need one of the allowed operator characters literally, escape it in your setting key.

Example Configuration

{
  "nix-embedded-languages.include": {
    "hcl|terraform": {
      "name": "HCL/Terraform",
      "scopeName": "source.hcl"
    }
  },
  "nix-embedded-languages.functionBindings": {
    "writeNushell|writeNu": "hcl"
  },
  "nix-embedded-languages.variableMarkers.suffix": {
    "Script": "shell"
  },
  "nix-embedded-languages.variableMarkers.prefix": {
    "py": "python"
  }
}

Requirements

• The Nix IDE extension (or another extension providing source.nix grammar)

Contributing

1. Install devenv
2. Load development environment:

devenv shell