target_spec/spec.rs
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// Copyright (c) The cargo-guppy Contributors
// SPDX-License-Identifier: MIT OR Apache-2.0
use crate::{
errors::{ExpressionParseError, PlainStringParseError},
Error, Platform, Triple,
};
use cfg_expr::{Expression, Predicate};
use std::{borrow::Cow, fmt, str::FromStr, sync::Arc};
/// A parsed target specification or triple string, as found in a `Cargo.toml` file.
///
/// ## Expressions and triple strings
///
/// Cargo supports [platform-specific
/// dependencies](https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#platform-specific-dependencies).
/// These dependencies can be specified in one of two ways:
///
/// ```toml
/// # 1. As Rust-like `#[cfg]` syntax.
/// [target.'cfg(all(unix, target_arch = "x86_64"))'.dependencies]
/// native = { path = "native/x86_64" }
///
/// # 2. Listing out the full target triple.
/// [target.x86_64-pc-windows-gnu.dependencies]
/// winhttp = "0.4.0"
/// ```
///
/// ### The `cfg()` syntax
///
/// The first [`cfg()` syntax](https://doc.rust-lang.org/reference/conditional-compilation.html) is
/// represented via the [`TargetSpec::Expression`] variant. This variant represents an arbitrary
/// expression against certain properties of the target. To evaluate a [`Platform`] against this
/// variant, `target-spec` builds an expression tree (currently via
/// [`cfg-expr`](https://github.com/EmbarkStudios/cfg-expr)).
///
/// ### Plain string syntax
///
/// The second syntax, listing just the name of a platform, is represented via the
/// [`TargetSpec::PlainString`] variant. In target-spec's model, the contained data is arbitrary
/// and used only for string comparisons. For example,
/// `TargetSpec::PlainString("x86_64-pc-windows-gnu")` will match the `x86_64-pc-windows-gnu`
/// platform.
///
/// `target-spec` checks that the string looks sufficiently like a triple. This check is duplicated
/// from Cargo's own check and is implemented in [`Self::looks_like_plain_string`].
///
/// ## Examples
///
/// ```
/// use target_spec::{Platform, TargetFeatures, TargetSpec};
///
/// let i686_windows = Platform::new("i686-pc-windows-gnu", TargetFeatures::Unknown).unwrap();
/// let x86_64_mac = Platform::new("x86_64-apple-darwin", TargetFeatures::none()).unwrap();
/// let i686_linux = Platform::new(
/// "i686-unknown-linux-gnu",
/// TargetFeatures::features(["sse2"].iter().copied()),
/// ).unwrap();
///
/// let spec: TargetSpec = "cfg(any(windows, target_arch = \"x86_64\"))".parse().unwrap();
/// assert_eq!(spec.eval(&i686_windows), Some(true), "i686 Windows");
/// assert_eq!(spec.eval(&x86_64_mac), Some(true), "x86_64 MacOS");
/// assert_eq!(spec.eval(&i686_linux), Some(false), "i686 Linux (should not match)");
///
/// let spec: TargetSpec = "cfg(any(target_feature = \"sse2\", target_feature = \"sse\"))".parse().unwrap();
/// assert_eq!(spec.eval(&i686_windows), None, "i686 Windows features are unknown");
/// assert_eq!(spec.eval(&x86_64_mac), Some(false), "x86_64 MacOS matches no features");
/// assert_eq!(spec.eval(&i686_linux), Some(true), "i686 Linux matches some features");
/// ```
#[derive(Clone, Debug)]
pub enum TargetSpec {
/// A complex expression.
///
/// Parsed from strings like `"cfg(any(windows, target_arch = \"x86_64\"))"`.
Expression(TargetSpecExpression),
/// A plain string representing a triple.
///
/// This string hasn't been validated because it may represent a custom platform. To validate
/// this string, use [`Self::is_known`].
PlainString(TargetSpecPlainString),
}
impl TargetSpec {
/// Creates a new target spec from a string.
pub fn new(input: impl Into<Cow<'static, str>>) -> Result<Self, Error> {
let input = input.into();
if Self::looks_like_expression(&input) {
match TargetSpecExpression::new(&input) {
Ok(expression) => Ok(Self::Expression(expression)),
Err(error) => Err(Error::InvalidExpression(error)),
}
} else {
match TargetSpecPlainString::new(input) {
Ok(plain_str) => Ok(Self::PlainString(plain_str)),
Err(error) => Err(Error::InvalidTargetSpecString(error)),
}
}
}
/// Returns true if the input will be parsed as a target expression.
///
/// In other words, returns true if the input begins with `"cfg("`.
pub fn looks_like_expression(input: &str) -> bool {
input.starts_with("cfg(")
}
/// Returns true if the input will be understood to be a plain string.
///
/// This check is borrowed from
/// [`cargo-platform`](https://github.com/rust-lang/cargo/blob/5febbe5587b74108165f748e79a4f8badbdf5e0e/crates/cargo-platform/src/lib.rs#L40-L63).
///
/// Note that this currently accepts an empty string. This matches Cargo's behavior as of Rust
/// 1.70.
pub fn looks_like_plain_string(input: &str) -> bool {
TargetSpecPlainString::validate(input).is_ok()
}
/// Returns true if an input looks like it's known and understood.
///
/// * For [`Self::Expression`], the inner [`TargetSpecExpression`] has already been parsed as
/// valid, so this returns true.
/// * For [`Self::PlainString`], this returns true if the string matches a builtin triple or has
/// heuristically been determined to be valid.
///
/// This method does not take into account custom platforms. If you know about custom platforms,
/// consider checking against those as well.
pub fn is_known(&self) -> bool {
match self {
TargetSpec::PlainString(plain_str) => {
Triple::new(plain_str.as_str().to_owned()).is_ok()
}
TargetSpec::Expression(_) => true,
}
}
/// Evaluates this specification against the given platform.
///
/// Returns `Some(true)` if there's a match, `Some(false)` if there's none, or `None` if the
/// result of the evaluation is unknown (typically found if target features are involved).
#[inline]
pub fn eval(&self, platform: &Platform) -> Option<bool> {
match self {
TargetSpec::PlainString(plain_str) => Some(platform.triple_str() == plain_str.as_str()),
TargetSpec::Expression(expr) => expr.eval(platform),
}
}
}
impl FromStr for TargetSpec {
type Err = Error;
fn from_str(input: &str) -> Result<Self, Self::Err> {
Self::new(input.to_owned())
}
}
impl fmt::Display for TargetSpec {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self {
TargetSpec::Expression(expr) => write!(f, "{expr}"),
TargetSpec::PlainString(plain_str) => write!(f, "{plain_str}"),
}
}
}
/// A target expression, parsed from a string beginning with `cfg(`.
///
/// For more information, see [`TargetSpec`].
#[derive(Clone, Debug)]
pub struct TargetSpecExpression {
inner: Arc<Expression>,
}
impl TargetSpecExpression {
/// Creates a new `TargetSpecExpression` from a string beginning with `cfg(`.
///
/// Returns an error if the string could not be parsed, or if the string contains a predicate
/// that wasn't understood by `target-spec`.
pub fn new(input: &str) -> Result<Self, ExpressionParseError> {
let expr = Expression::parse(input).map_err(|err| ExpressionParseError::new(input, err))?;
Ok(Self {
inner: Arc::new(expr),
})
}
/// Returns the string that was parsed into `self`.
#[inline]
pub fn expression_str(&self) -> &str {
self.inner.original()
}
/// Evaluates this expression against the given platform.
///
/// Returns `Some(true)` if there's a match, `Some(false)` if there's none, or `None` if the
/// result of the evaluation is unknown (typically found if target features are involved).
pub fn eval(&self, platform: &Platform) -> Option<bool> {
self.inner.eval(|pred| {
match pred {
Predicate::Target(target) => Some(platform.triple().matches(target)),
Predicate::TargetFeature(feature) => platform.target_features().matches(feature),
Predicate::Test | Predicate::DebugAssertions | Predicate::ProcMacro => {
// Known families that always evaluate to false. See
// https://docs.rs/cargo-platform/0.1.1/src/cargo_platform/lib.rs.html#76.
Some(false)
}
Predicate::Feature(_) => {
// NOTE: This is not supported by Cargo which always evaluates this to false. See
// https://github.com/rust-lang/cargo/issues/7442 for more details.
Some(false)
}
Predicate::Flag(flag) => {
// This returns false by default but true in some cases.
Some(platform.has_flag(flag))
}
Predicate::KeyValue { .. } => {
// This is always interpreted by Cargo as false.
Some(false)
}
}
})
}
}
impl FromStr for TargetSpecExpression {
type Err = ExpressionParseError;
fn from_str(input: &str) -> Result<Self, Self::Err> {
Self::new(input)
}
}
impl fmt::Display for TargetSpecExpression {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(self.expression_str())
}
}
/// A plain string as contained within a [`TargetSpec::PlainString`].
///
/// For more information, see [`TargetSpec`].
#[derive(Clone, Debug)]
pub struct TargetSpecPlainString(Cow<'static, str>);
impl TargetSpecPlainString {
/// Creates a new instance of `TargetSpecPlainString`, after validating it.
pub fn new(input: impl Into<Cow<'static, str>>) -> Result<Self, PlainStringParseError> {
let input = input.into();
Self::validate(&input)?;
Ok(Self(input))
}
/// Returns the string as parsed.
pub fn as_str(&self) -> &str {
&self.0
}
fn validate(input: &str) -> Result<(), PlainStringParseError> {
if let Some((char_index, c)) = input
.char_indices()
.find(|&(_, c)| !(c.is_alphanumeric() || c == '_' || c == '-' || c == '.'))
{
Err(PlainStringParseError::new(input.to_owned(), char_index, c))
} else {
Ok(())
}
}
}
impl FromStr for TargetSpecPlainString {
type Err = PlainStringParseError;
fn from_str(input: &str) -> Result<Self, Self::Err> {
Self::new(input.to_owned())
}
}
impl fmt::Display for TargetSpecPlainString {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str(&self.0)
}
}
#[cfg(test)]
mod tests {
use super::*;
use cfg_expr::{
targets::{Abi, Arch, Family, Os},
Predicate, TargetPredicate,
};
#[test]
fn test_triple() {
let res = TargetSpec::new("x86_64-apple-darwin");
assert!(matches!(
res,
Ok(TargetSpec::PlainString(triple)) if triple.as_str() == "x86_64-apple-darwin"
));
}
#[test]
fn test_single() {
let expr = match TargetSpec::new("cfg(windows)").unwrap() {
TargetSpec::PlainString(triple) => {
panic!("expected expression, got triple: {:?}", triple)
}
TargetSpec::Expression(expr) => expr,
};
assert_eq!(
expr.inner.predicates().collect::<Vec<_>>(),
vec![Predicate::Target(TargetPredicate::Family(Family::windows))],
);
}
#[test]
fn test_target_abi() {
let expr =
match TargetSpec::new("cfg(any(target_arch = \"wasm32\", target_abi = \"unknown\"))")
.unwrap()
{
TargetSpec::PlainString(triple) => {
panic!("expected expression, got triple: {:?}", triple)
}
TargetSpec::Expression(expr) => expr,
};
assert_eq!(
expr.inner.predicates().collect::<Vec<_>>(),
vec![
Predicate::Target(TargetPredicate::Arch(Arch("wasm32".into()))),
Predicate::Target(TargetPredicate::Abi(Abi("unknown".into()))),
],
);
}
#[test]
fn test_not() {
assert!(matches!(
TargetSpec::new("cfg(not(windows))"),
Ok(TargetSpec::Expression(_))
));
}
#[test]
fn test_testequal() {
let expr = match TargetSpec::new("cfg(target_os = \"windows\")").unwrap() {
TargetSpec::PlainString(triple) => {
panic!("expected spec, got triple: {:?}", triple)
}
TargetSpec::Expression(expr) => expr,
};
assert_eq!(
expr.inner.predicates().collect::<Vec<_>>(),
vec![Predicate::Target(TargetPredicate::Os(Os::windows))],
);
}
#[test]
fn test_identifier_like_triple() {
// This used to be "x86_64-pc-darwin", but target-lexicon can parse that.
let spec = TargetSpec::new("cannotbeknown")
.expect("triples that look like identifiers should parse correctly");
assert!(!spec.is_known(), "spec isn't known");
}
#[test]
fn test_triple_string_identifier() {
// We generally trust that unicode-ident is correct. Just do some basic checks.
let valid = ["", "foo", "foo-bar", "foo_baz", "-foo", "quux-"];
let invalid = ["foo+bar", "foo bar", " "];
for input in valid {
assert!(
TargetSpec::looks_like_plain_string(input),
"`{input}` looks like triple string"
);
}
for input in invalid {
assert!(
!TargetSpec::looks_like_plain_string(input),
"`{input}` does not look like triple string"
);
}
}
#[test]
fn test_unknown_triple() {
// This used to be "x86_64-pc-darwin", but target-lexicon can parse that.
let err = TargetSpec::new("cannotbeknown!!!")
.expect_err("unknown triples should parse correctly");
assert!(matches!(
err,
Error::InvalidTargetSpecString(s) if s.input == "cannotbeknown!!!"
));
}
#[test]
fn test_unknown_flag() {
let expr = match TargetSpec::new("cfg(foo)").unwrap() {
TargetSpec::PlainString(triple) => {
panic!("expected spec, got triple: {:?}", triple)
}
TargetSpec::Expression(expr) => expr,
};
assert_eq!(
expr.inner.predicates().collect::<Vec<_>>(),
vec![Predicate::Flag("foo")],
);
}
#[test]
fn test_unknown_predicate() {
let expr = match TargetSpec::new("cfg(bogus_key = \"bogus_value\")")
.expect("unknown predicate should parse")
{
TargetSpec::PlainString(triple) => {
panic!("expected spec, got triple: {:?}", triple)
}
TargetSpec::Expression(expr) => expr,
};
assert_eq!(
expr.inner.predicates().collect::<Vec<_>>(),
vec![Predicate::KeyValue {
key: "bogus_key",
val: "bogus_value"
}],
);
let platform = Platform::current().unwrap();
// This should always evaluate to false.
assert_eq!(expr.eval(&platform), Some(false));
let expr = TargetSpec::new("cfg(not(bogus_key = \"bogus_value\"))")
.expect("unknown predicate should parse");
// This is a cfg(not()), so it should always evaluate to true.
assert_eq!(expr.eval(&platform), Some(true));
}
#[test]
fn test_extra() {
let res = TargetSpec::new("cfg(unix)this-is-extra");
res.expect_err("extra content at the end");
}
#[test]
fn test_incomplete() {
// This fails because the ) at the end is missing.
let res = TargetSpec::new("cfg(not(unix)");
res.expect_err("missing ) at the end");
}
}