Crate version_check

This tiny crate checks that the running or installed rustc meets some version requirements. The version is queried by calling the Rust compiler with --version. The path to the compiler is determined first via the RUSTC environment variable. If it is not set, then rustc is used. If that fails, no determination is made, and calls return None.

Examples

• Set a cfg flag in build.rs if the running compiler was determined to be at least version 1.13.0:

  extern crate version_check as rustc;
  
  if rustc::is_min_version("1.13.0").unwrap_or(false) {
      println!("cargo:rustc-cfg=question_mark_operator");
  }

  See is_max_version or is_exact_version to check if the compiler is at most or exactly a certain version.

• Check that the running compiler was released on or after 2018-12-18:

  extern crate version_check as rustc;
  
  match rustc::is_min_date("2018-12-18") {
      Some(true) => "Yep! It's recent!",
      Some(false) => "No, it's older.",
      None => "Couldn't determine the rustc version."
  };

  See is_max_date or is_exact_date to check if the compiler was released prior to or exactly on a certain date.

• Check that the running compiler supports feature flags:

  extern crate version_check as rustc;
  
  match rustc::is_feature_flaggable() {
      Some(true) => "Yes! It's a dev or nightly release!",
      Some(false) => "No, it's stable or beta.",
      None => "Couldn't determine the rustc version."
  };

• Check that the running compiler supports a specific feature:

  extern crate version_check as rustc;
  
  if let Some(true) = rustc::supports_feature("doc_cfg") {
     println!("cargo:rustc-cfg=has_doc_cfg");
  }

• Check that the running compiler is on the stable channel:

  extern crate version_check as rustc;
  
  match rustc::Channel::read() {
      Some(c) if c.is_stable() => format!("Yes! It's stable."),
      Some(c) => format!("No, the channel {} is not stable.", c),
      None => format!("Couldn't determine the rustc version.")
  };

To interact with the version, release date, and release channel as structs, use Version, Date, and Channel, respectively. The triple() function returns all three values efficiently.

Alternatives

This crate is dead simple with no dependencies. If you need something more and don’t care about panicking if the version cannot be obtained, or if you don’t mind adding dependencies, see rustc_version.

Structs

Channel

Release channel: “dev”, “nightly”, “beta”, or “stable”.

Date

Release date including year, month, and day.

Version

Version number: major.minor.patch, ignoring release channel.

Functions

is_exact_date

Checks that the running or installed rustc was released exactly on some date.

is_exact_version

Checks that the running or installed rustc is exactly some version.

is_feature_flaggable

Checks whether the running or installed rustc supports feature flags.

is_max_date

Checks that the running or installed rustc was released on or before some date.

is_max_version

Checks that the running or installed rustc is at most some maximum version.

is_min_date

Checks that the running or installed rustc was released on or after some date.

is_min_version

Checks that the running or installed rustc is at least some minimum version.

supports_feature

Checks whether the running or installed rustc supports feature.

triple

Reads the triple of Version, Channel, and Date of the installed or running rustc.