sass/spec/declarations.md

Declarations

Table of Contents

• Syntax
• Definitions
• Current Declaration Name
• Semantics

Syntax

Declaration         ::= StandardDeclaration | CustomDeclaration
StandardDeclaration ::= InterpolatedIdentifier¹ ':' (Value | Value? '{' Statements '}')
CustomDeclaration   ::= InterpolatedIdentifier² ':' InterpolatedDeclarationValue

1. This may not begin with "--".
2. This must begin with "--".

Definitions

Current Declaration Name

The current declaration name is the innermost value declared as such when executing a declaration.

Semantics

To execute a declaration declaration:

• Let parent-name be the current declaration name, if one exists.

• If name is set and declaration is a CustomDeclaration, throw an error.

• Let name be the result of evaluating the all interpolation in declaration's name.

• If parent-name exists, set name to parent-name + "-" + name.

• Declare name as the current declaration name for the duration of executing declaration.

• If declaration has a Value:

  • Let value be the result of evaluating that Value.

• Otherwise, if declaration is a CustomDeclaration:

  • Let value be an unquoted string whose value is the result of evaluating declaration's InterpolatedDeclarationValue.

  • If value is empty, throw an error.

    Note that value being only whitespace is allowed, including --foo: ;.

• Let parent be the current style rule, keyframe block, or at-rule; or the innermost if multiple exist.

  Parsing guarantees that a declaration will have at least one parent.

• If value is set, and it's neither null nor an empty unquoted string:

  • Let css be a CSS declaration with name name and value value.

  • Append css to parent.

• Evaluate each child in declaration's Statements if it exists.