Struct SpecUnknownEnv 

#[non_exhaustive]
pub struct SpecUnknownEnv {
    pub prefix: String,
    pub allow: Vec<String>,
}

Refuse environment variables under the application’s prefix that nothing declares.

unknown_flags "error" turns a misspelled flag into an error. A misspelled or stale environment variable gets no such check by default — MYAPP_LISTEN_TLS_CRET is read by nobody, and the program runs on its defaults. That failure is worst where nobody watches a command line: systemd units, container manifests, Helm values.

unknown_env prefix="MOQ_" {
    allow "MOQ_VAAPI_DEVICE" "MOQ_V4L2_ENCODER"
}

The prefix only scopes the check. It never builds a name: every variable is still spelled out in full where it is declared, so a name seen in an environment can be found by searching for it.

A variable is known when any flag or argument anywhere in the command tree names it — as env, an env_fallback or a deprecated_env — or when a config property reads it, or when it is listed in allow. The whole tree counts, not only the command that ran: a variable meant for serve is not a typo when the user runs publish. allow is for variables read outside the spec, such as by a library.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

prefix: String

Only variables whose names start with this are checked.

allow: Vec<String>

Variables under the prefix that the spec does not declare but something still reads.

Implementations

impl SpecUnknownEnv

pub fn new(prefix: impl Into<String>) -> Self

pub fn allow(self, name: impl Into<String>) -> Self

A variable read outside the spec, which is therefore not a mistake.

pub fn unknown<'n>( &self, spec: &Spec, names: impl IntoIterator<Item = &'n OsStr>, ) -> Vec<String>

The variables under the prefix that spec neither declares nor allows, sorted.

names is the environment’s variable names. A name that is not valid UTF-8 cannot be one the spec declares, so one under the prefix is reported in its lossy spelling rather than skipped.

Trait Implementations

impl Clone for SpecUnknownEnv

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for SpecUnknownEnv

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

Formats the value using the given formatter.

impl Default for SpecUnknownEnv

fn default() -> Self

Returns the “default value” for a type.

impl Eq for SpecUnknownEnv

impl PartialEq for SpecUnknownEnv

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

Equality operator ==.

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

Inequality operator !=.

impl Serialize for SpecUnknownEnv

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

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for SpecUnknownEnv