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// =============================================================================
// Copyright (c) 2025 - 2026 Haixing Hu.
//
// SPDX-License-Identifier: Apache-2.0
//
// Licensed under the Apache License, Version 2.0.
// =============================================================================
//! Strict parsing boundary for container-level `redact` attributes.
use syn::{
DeriveInput,
Meta,
Token,
};
/// Parsed container controls for optional redacted serde integration.
#[must_use]
pub(crate) struct ContainerAttributes {
/// Whether the original type should receive a redacted `Debug` impl.
debug: bool,
/// Whether the original type should receive a redacted `Display` impl.
display: bool,
/// Whether redacted serde integration was requested.
serde: bool,
/// Whether mutable redaction generation was disabled.
no_mut: bool,
/// Whether every field must declare an explicit redaction mode.
require_explicit: bool,
}
impl ContainerAttributes {
/// Parses and validates container-level attributes on `input`.
///
/// # Parameters
///
/// * `input` - Complete derive input whose container attributes are read.
///
/// # Returns
///
/// Validated optional formatting, serialization, mutable-redaction, and
/// explicit-field controls.
///
/// # Errors
///
/// Returns a targeted error for malformed, repeated, or unsupported
/// container controls.
pub(crate) fn parse(input: &DeriveInput) -> syn::Result<Self> {
let mut debug = false;
let mut display = false;
let mut serde = false;
let mut no_mut = false;
let mut require_explicit = false;
for attribute in &input.attrs {
if !attribute.path().is_ident("redact") {
continue;
}
let Meta::List(list) = &attribute.meta else {
return Err(syn::Error::new_spanned(
attribute,
format!(
"Redact derive for `{}` expects `#[redact(debug, display, serde, no_mut, require_explicit)]` on the container",
input.ident,
),
));
};
if list.tokens.is_empty() {
return Err(syn::Error::new_spanned(
attribute,
format!(
"Redact derive for `{}` does not allow an empty container attribute; use \
`#[redact(debug)]`, `#[redact(display)]`, `#[redact(serde)]`, \
`#[redact(no_mut)]`, or `#[redact(require_explicit)]`",
input.ident,
),
));
}
attribute.parse_nested_meta(|meta| {
let option = if meta.path.is_ident("debug") {
&mut debug
} else if meta.path.is_ident("display") {
&mut display
} else if meta.path.is_ident("serde") {
&mut serde
} else if meta.path.is_ident("no_mut") {
&mut no_mut
} else if meta.path.is_ident("require_explicit") {
&mut require_explicit
} else {
return Err(meta.error(format!(
"Redact derive for `{}` has unknown container attribute; use \
`debug`, `display`, `serde`, `no_mut`, or `require_explicit`",
input.ident,
)));
};
if meta.input.peek(Token![=]) || meta.input.peek(syn::token::Paren) {
let name = meta
.path
.segments
.last()
.map_or("option".to_owned(), |segment| segment.ident.to_string());
return Err(meta.error(format!(
"Redact derive for `{}` requires bare `{name}` without arguments",
input.ident
)));
}
if *option {
let name = meta
.path
.segments
.last()
.map_or("option".to_owned(), |segment| segment.ident.to_string());
return Err(meta.error(format!(
"Redact derive for `{}` repeats the `{name}` container option",
input.ident
)));
}
*option = true;
Ok(())
})?;
}
Ok(Self {
debug,
display,
serde,
no_mut,
require_explicit,
})
}
/// Returns whether this struct requested a redacted `Debug` impl.
///
/// # Returns
///
/// `true` when the `debug` container option was present.
#[must_use]
#[inline(always)]
pub(crate) const fn debug_enabled(&self) -> bool {
self.debug
}
/// Returns whether this struct requested a redacted `Display` impl.
///
/// # Returns
///
/// `true` when the `display` container option was present.
#[must_use]
#[inline(always)]
pub(crate) const fn display_enabled(&self) -> bool {
self.display
}
/// Returns whether this struct requested redacted serialization.
///
/// # Returns
///
/// `true` when the `serde` container option was present.
#[must_use]
#[inline(always)]
pub(crate) const fn serde_enabled(&self) -> bool {
self.serde
}
/// Returns whether mutable redaction generation was disabled.
///
/// # Returns
///
/// `true` when the `no_mut` container option was present.
#[must_use]
#[inline(always)]
pub(crate) const fn mutable_disabled(&self) -> bool {
self.no_mut
}
/// Returns whether every field must select an explicit redaction mode.
///
/// # Returns
///
/// `true` when the `require_explicit` container option was present.
#[must_use]
#[inline(always)]
pub(crate) const fn require_explicit(&self) -> bool {
self.require_explicit
}
}