DynamicKey (Dynamic Attribute Key)

Definition

DynamicKey (Antiquoted String)

Fields

Description

DynamicKey is used for attribute keys that are not static identifiers: either quoted strings like "foo bar" or antiquoted expressions like ${name}. In Nix, any key in quotes or with antiquotation is parsed as a DynamicKey.

The contents is an Antiquoted String, meaning it can be:

• Plain string parts
• Antiquoted expressions
• Escaped newlines (in indented strings)

Nix Source ↔ AST

Quoted String Key

# Nix
{ "foo bar" = 1; }

# AST (key part)
{
  "tag": "DynamicKey",
  "contents": {
    "tag": "Plain",
    "contents": {
      "tag": "DoubleQuoted",
      "contents": [
        { "tag": "Plain", "contents": "foo bar" }
      ]
    }
  }
}

Antiquoted Key

# Nix
let name = "foo"; in { ${name} = 1; }

# AST (key part)
{
  "tag": "DynamicKey",
  "contents": {
    "tag": "Antiquoted",
    "contents": { "tag": "Sym", "contents": "name" }
  }
}

Related

• StaticKey: static identifier keys
• String: DoubleQuoted / Indented string nodes
• Antiquoted: string parts
• NamedVar: uses AttrPath of KeyName

Nix Library Access

syntax.mkDynamicKey (syntax.mkAntiquoted (syntax.mkSym "name"))
# Plain + String variant (rare): syntax.mkDynamicKey (syntax.mkPlain (syntax.mkDoubleQuoted [...]))