mirror of
https://gitee.com/openharmony/third_party_rust_version_check
synced 2024-11-22 23:40:02 +00:00
Add 'supports_feature()'.
This commit is contained in:
Sergio Benitez
parent
7d81cbd242
commit
32693c9ff9
140
src/lib.rs
140
src/lib.rs
@ -6,58 +6,68 @@
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//!
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//! # Examples
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//!
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//! Set a `cfg` flag in `build.rs` if the running compiler was determined to be
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//! at least version `1.13.0`:
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//! * Set a `cfg` flag in `build.rs` if the running compiler was determined to
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//! be at least version `1.13.0`:
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//!
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//! ```rust
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//! extern crate version_check as rustc;
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//! ```rust
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//! extern crate version_check as rustc;
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//!
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//! if rustc::is_min_version("1.13.0").unwrap_or(false) {
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//! println!("cargo:rustc-cfg=question_mark_operator");
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//! }
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//! ```
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//! if rustc::is_min_version("1.13.0").unwrap_or(false) {
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//! println!("cargo:rustc-cfg=question_mark_operator");
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//! }
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//! ```
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//!
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//! See [`is_max_version`] or [`is_exact_version`] to check if the compiler
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//! is _at most_ or _exactly_ a certain version.
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//! See [`is_max_version`] or [`is_exact_version`] to check if the compiler
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//! is _at most_ or _exactly_ a certain version.
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//!
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//! Check that the running compiler was released on or after `2018-12-18`:
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//! * Check that the running compiler was released on or after `2018-12-18`:
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//!
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//! ```rust
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//! extern crate version_check as rustc;
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//! ```rust
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//! extern crate version_check as rustc;
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//!
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//! match rustc::is_min_date("2018-12-18") {
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//! Some(true) => "Yep! It's recent!",
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//! Some(false) => "No, it's older.",
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//! None => "Couldn't determine the rustc version."
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//! };
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//! ```
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//! match rustc::is_min_date("2018-12-18") {
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//! Some(true) => "Yep! It's recent!",
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//! Some(false) => "No, it's older.",
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//! None => "Couldn't determine the rustc version."
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//! };
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//! ```
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//!
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//! See [`is_max_date`] or [`is_exact_date`] to check if the compiler was
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//! released _prior to_ or _exactly on_ a certain date.
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//! See [`is_max_date`] or [`is_exact_date`] to check if the compiler was
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//! released _prior to_ or _exactly on_ a certain date.
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//!
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//! Check that the running compiler supports feature flags:
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//! * Check that the running compiler supports feature flags:
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//!
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//! ```rust
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//! extern crate version_check as rustc;
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//! ```rust
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//! extern crate version_check as rustc;
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//!
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//! match rustc::is_feature_flaggable() {
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//! Some(true) => "Yes! It's a dev or nightly release!",
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//! Some(false) => "No, it's stable or beta.",
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//! None => "Couldn't determine the rustc version."
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//! };
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//! ```
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//! match rustc::is_feature_flaggable() {
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//! Some(true) => "Yes! It's a dev or nightly release!",
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//! Some(false) => "No, it's stable or beta.",
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//! None => "Couldn't determine the rustc version."
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//! };
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//! ```
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//!
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//! Check that the running compiler is on the stable channel:
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//! * Check that the running compiler supports a specific feature:
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//!
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//! ```rust
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//! extern crate version_check as rustc;
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//! ```rust
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//! extern crate version_check as rustc;
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//!
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//! match rustc::Channel::read() {
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//! Some(c) if c.is_stable() => format!("Yes! It's stable."),
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//! Some(c) => format!("No, the channel {} is not stable.", c),
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//! None => format!("Couldn't determine the rustc version.")
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//! };
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//! ```
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//! if let Some(true) = rustc::supports_feature("doc_cfg") {
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//! println!("cargo:rustc-cfg=has_doc_cfg");
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//! }
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//! ```
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//!
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//! * Check that the running compiler is on the stable channel:
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//!
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//! ```rust
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//! extern crate version_check as rustc;
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//!
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//! match rustc::Channel::read() {
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//! Some(c) if c.is_stable() => format!("Yes! It's stable."),
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//! Some(c) => format!("No, the channel {} is not stable.", c),
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//! None => format!("Couldn't determine the rustc version.")
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//! };
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//! ```
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//!
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//! To interact with the version, release date, and release channel as structs,
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//! use [`Version`], [`Date`], and [`Channel`], respectively. The [`triple()`]
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@ -248,12 +258,64 @@ pub fn is_exact_version(version: &str) -> Option<bool> {
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///
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/// In other words, if the channel is either "nightly" or "dev".
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///
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/// Note that support for specific `rustc` features can be enabled or disabled
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/// via the `allow-features` compiler flag, which this function _does not_
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/// check. That is, this function _does not_ check whether a _specific_ feature
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/// is supported, but instead whether features are supported at all. To check
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/// for support for a specific feature, use [`supports_feature()`].
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///
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/// If the version could not be determined, returns `None`. Otherwise returns
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/// `true` if the running version supports feature flags and `false` otherwise.
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pub fn is_feature_flaggable() -> Option<bool> {
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Channel::read().map(|c| c.supports_features())
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}
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/// Checks whether the running or installed `rustc` supports `feature`.
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///
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/// Returns _true_ _iff_ [`is_feature_flaggable()`] returns `true` _and_ the
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/// feature is not disabled via exclusion in `allow-features` via `RUSTFLAGS` or
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/// `CARGO_ENCODED_RUSTFLAGS`. If the version could not be determined, returns
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/// `None`.
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///
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/// # Example
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///
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/// ```rust
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/// use version_check as rustc;
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///
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/// if let Some(true) = rustc::supports_feature("doc_cfg") {
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/// println!("cargo:rustc-cfg=has_doc_cfg");
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/// }
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/// ```
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pub fn supports_feature(feature: &str) -> Option<bool> {
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match is_feature_flaggable() {
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Some(true) => { /* continue */ }
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Some(false) => return Some(false),
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None => return None,
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}
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let env_flags = env::var_os("CARGO_ENCODED_RUSTFLAGS")
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.map(|flags| (flags, '\x1f'))
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.or_else(|| env::var_os("RUSTFLAGS").map(|flags| (flags, ' ')));
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if let Some((flags, delim)) = env_flags {
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const ALLOW_FEATURES: &'static str = "allow-features=";
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let rustflags = flags.to_string_lossy();
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let allow_features = rustflags.split(delim)
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.map(|flag| flag.trim_left_matches("-Z").trim())
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.filter(|flag| flag.starts_with(ALLOW_FEATURES))
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.map(|flag| &flag[ALLOW_FEATURES.len()..]);
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if let Some(allow_features) = allow_features.last() {
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return Some(allow_features.split(',').any(|f| f.trim() == feature));
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}
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}
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// If there are no `RUSTFLAGS` or `CARGO_ENCODED_RUSTFLAGS` or they don't
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// contain an `allow-features` flag, assume compiler allows all features.
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Some(true)
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}
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#[cfg(test)]
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mod tests {
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use std::{env, fs};
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