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variables.md

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Variables

Table of Contents

Syntax

Variable            ::= PlainVariable | NamespacedVariable
PlainVariable       ::= '$' <ident-token>
NamespacedVariable  ::= <ident-token> '.$' PublicIdentifier
VariableDeclaration ::= Variable ':' Expression ('!global' | '!default')*

No whitespace is allowed after the $ in PlainVariable or before or after the .$ in NamespacedVariable. Each of !global and !default is allowed at most once in VariableDeclaration. As with all statements, a VariableDeclaration must be separated from other statements with a semicolon.

Definitions

Scope

A scope is a mapping from variable names to values. Every block of statements delimited by { and } in SCSS or by indentation in the indented syntax has an associated scope.

Global Scope

The global scope is the scope shared among the top level of all Sass files.

Semantics

Executing a Variable Declaration

To execute a VariableDeclaration declaration:

  • Let value be the result of evaluating declaration's Expression.

  • Let name be declaration's Variable.

  • Let resolved be the result of resolving a variable named name.

  • If name is a NamespacedVariable and declaration has a !global flag, throw an error.

  • Otherwise, if resolved is a variable from a built-in module, throw an error.

  • Otherwise, if declaration is outside of any block of statements, or declaration has a !global flag, or name is a NamespacedVariable:

    • If declaration has a !default flag, resolved isn't null, and resolved's value isn't null, do nothing.

    • Otherwise, if resolved is a variable in another module:

      • Evaluate declaration's value and set resolved's value to the result.

    • Otherwise:

      • If declaration is outside of any block of statements, it has a !default flag, and config contains a variable named name whose value is not null:

        • Let value be the value of config's variable named name.

      • Otherwise, let value be the result of evaluating declaration's value.

      • If name doesn't begin with - or _, add a variable with name name and value value to module.

        This overrides the previous definition, if one exists.

      • Add a variable with name name and value value to import.

        This also overrides the previous definition.

  • Otherwise, if declaration is within one or more blocks associated with @if, @each, @for, and/or @while rules and no other blocks:

    • If resolved is not null:

      • If declaration has a !default flag and resolved's value isn't null, do nothing.

      • Otherwise, let value be the result of evaluating declaration's value.

      • If name doesn't begin with - or _, add a variable with name name and value value to module.

        This overrides the previous definition, if one exists.

      • Add a variable with name name and value value to import.

        This also overrides the previous definition.

  • Otherwise, if resolved is null, get the innermost block containing declaration and set its scope's variable name to value.

  • Otherwise, set resolved's value to value.

Evaluating a Variable

To evaluate a Variable variable:

  • Let definition be the result of resolving a variable named variable. If this returns null, throw an error.

  • Return definition's value.