Enum ParamValue 

pub enum ParamValue {
    One(String),
    Many(Vec<String>),
}

What one parameter holds: a value, or several.

ADR-0022. A parameter is single-valued unless its declaration says otherwise, and both shapes live in the same map because a binding stores one map whatever its parameters declared.

Why an enum rather than always a list

Because of what it costs on disk. #[serde(untagged)] renders these as app = "spotify" and apps = ["discord", "game"] in the same TOML table, so a configuration written before lists existed parses unchanged and needs no migration rung. Making every value a list would have rewritten every binding anybody has, to express something almost none of them use.

It is also what 006-FR-024a-i asks for in the negative: a list “MUST be widened rather than worked around with a delimiter convention the interface cannot render”. A TOML array is how TOML writes a list. There is no convention to learn, and nothing to escape.

Variants

One(String)

One value. What every parameter was before ADR-0022.

Many(Vec<String>)

Several, in the order the user arranged them.

Implementations

impl ParamValue

pub fn one(&self) -> Option<&str>

The single value, or None if this holds a list.

Not the first element, deliberately. An addon that declared a single-valued parameter and receives a list has been given something it did not ask for, and quietly using the first entry would silently ignore the rest — the failure being a key that mutes one of the three applications somebody named. None reaches the required-parameter check in Registry::perform and fails loudly instead.

pub fn all(&self) -> Vec<&str>

Every value, whether this holds one or several.

A single value reads as a list of one, because an addon that declared multiple should not have to care how the user happened to fill it in — and a file written before lists existed contains exactly that case. Empty strings are dropped for the same reason Self::one rejects them: a cleared box is not a configured value.

Trait Implementations

impl Clone for ParamValue

fn clone(&self) -> ParamValue

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ParamValue

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for ParamValue

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl From<&str> for ParamValue

fn from(v: &str) -> Self

Converts to this type from the input type.

impl PartialEq for ParamValue

fn eq(&self, other: &ParamValue) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for ParamValue

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for ParamValue

impl StructuralPartialEq for ParamValue