Introduce CARGO_PKG_EDITION env var

Solves rust-lang#14872

crates/build-rs/src/input.rs

@@ -536,6 +536,12 @@ pub fn cargo_pkg_license_file() -> Option<PathBuf> {
     to_opt(var_or_panic("CARGO_PKG_LICENSE_FILE")).map(to_path)
 }
 
+/// The Rust language edition from the manifest of your package.
+#[track_caller]
+pub fn cargo_pkg_edition() -> Option<String> {
+    to_opt(var_or_panic("CARGO_PKG_EDITION")).map(to_string)
+}
+
 /// The Rust version from the manifest of your package. Note that this is the
 /// minimum Rust version supported by the package, not the current Rust version.
 #[track_caller]

src/cargo/core/compiler/compilation.rs

@@ -361,6 +361,7 @@ impl<'gctx> Compilation<'gctx> {
         // consider adding the corresponding properties to the hash
         // in BuildContext::target_metadata()
         let rust_version = pkg.rust_version().as_ref().map(ToString::to_string);
+        let edition = pkg.edition();
         cmd.env("CARGO_MANIFEST_DIR", pkg.root())
             .env("CARGO_MANIFEST_PATH", pkg.manifest_path())
             .env("CARGO_PKG_VERSION_MAJOR", &pkg.version().major.to_string())
@@ -390,6 +391,10 @@ impl<'gctx> Compilation<'gctx> {
                 metadata.license_file.as_ref().unwrap_or(&String::new()),
             )
             .env("CARGO_PKG_AUTHORS", &pkg.authors().join(":"))
+            .env(
+                "CARGO_PKG_EDITION",
+                edition.to_string(),
+            )
             .env(
                 "CARGO_PKG_RUST_VERSION",
                 &rust_version.as_deref().unwrap_or_default(),

src/cargo/core/package.rs

@@ -22,10 +22,7 @@ use crate::core::compiler::{CompileKind, RustcTargetData};
 use crate::core::dependency::DepKind;
 use crate::core::resolver::features::ForceAllTargets;
 use crate::core::resolver::{HasDevUnits, Resolve};
-use crate::core::{
-    CliUnstable, Dependency, Features, Manifest, PackageId, PackageIdSpec, SerializedDependency,
-    SourceId, Target,
-};
+use crate::core::{CliUnstable, Dependency, Edition, Features, Manifest, PackageId, PackageIdSpec, SerializedDependency, SourceId, Target};
 use crate::core::{Summary, Workspace};
 use crate::sources::source::{MaybePackage, SourceMap};
 use crate::util::cache_lock::{CacheLock, CacheLockMode};
@@ -167,6 +164,10 @@ impl Package {
     pub fn proc_macro(&self) -> bool {
         self.targets().iter().any(|target| target.proc_macro())
     }
+    /// Gets the package's language edition
+    pub fn edition(&self) -> Edition {
+        self.manifest().edition()
+    }
     /// Gets the package's minimum Rust version.
     pub fn rust_version(&self) -> Option<&RustVersion> {
         self.manifest().rust_version()

src/doc/src/reference/environment-variables.md

@@ -239,6 +239,7 @@ corresponding environment variable is set to the empty string, `""`.
 * `CARGO_PKG_REPOSITORY` --- The repository from the manifest of your package.
 * `CARGO_PKG_LICENSE` --- The license from the manifest of your package.
 * `CARGO_PKG_LICENSE_FILE` --- The license file from the manifest of your package.
+* `CARGO_PKG_EDITION` --- The Rust language edition from the manifest of your package.
 * `CARGO_PKG_RUST_VERSION` --- The Rust version from the manifest of your package.
   Note that this is the minimum Rust version supported by the package, not the
   current Rust version.

tests/testsuite/build.rs

@@ -1628,6 +1628,7 @@ fn crate_env_vars() {
                 static LICENSE: &'static str = env!("CARGO_PKG_LICENSE");
                 static LICENSE_FILE: &'static str = env!("CARGO_PKG_LICENSE_FILE");
                 static DESCRIPTION: &'static str = env!("CARGO_PKG_DESCRIPTION");
+                static EDITION: &'static str = env!("CARGO_PKG_EDITION");
                 static RUST_VERSION: &'static str = env!("CARGO_PKG_RUST_VERSION");
                 static README: &'static str = env!("CARGO_PKG_README");
                 static BIN_NAME: &'static str = env!("CARGO_BIN_NAME");