Auto merge of #8037 - djc:rfc-2495, r=ehuss

Implement support for rust-version field in project metadata

Needs a bunch more work, but I'd like some early feedback! Remaining work:

- [x] Bikeshedding name (picked `rust-version` here over `msrv` or `min-rust-version`)
- [x] Failing test for local dependency with unsatisfied MSRV
- [x] Requirement cannot be smaller than 1.27
- [x] Requirement cannot be smaller than initial release of edition used
- [x] Check for `run`, `verify` and `publish` subcommands
- [x] More tests (would love feedback on this)
- [x] Handle pre-release identifiers
- [x] Disallow semver range operators
- [x] Feature gate it
- [x] Add documentation for unstable feature

Minimal version of `@moxian's` earlier take in #7801.

cc rust-lang/rust#65262

Author: bors

crates/cargo-test-support/Cargo.toml

@@ -19,4 +19,5 @@ lazy_static = "1.0"
 remove_dir_all = "0.5"
 serde_json = "1.0"
 tar = { version = "0.4.18", default-features = false }
+toml = "0.5.7"
 url = "2.0"

crates/cargo-test-support/src/registry.rs

@@ -146,6 +146,8 @@ pub struct Package {
     invalid_json: bool,
     proc_macro: bool,
     links: Option<String>,
+    rust_version: Option<String>,
+    cargo_features: Vec<String>,
 }
 
 #[derive(Clone)]
@@ -247,6 +249,8 @@ impl Package {
             invalid_json: false,
             proc_macro: false,
             links: None,
+            rust_version: None,
+            cargo_features: Vec::new(),
         }
     }
 
@@ -363,6 +367,12 @@ impl Package {
         self
     }
 
+    /// Specify a minimal Rust version.
+    pub fn rust_version(&mut self, rust_version: &str) -> &mut Package {
+        self.rust_version = Some(rust_version.into());
+        self
+    }
+
     /// Causes the JSON line emitted in the index to be invalid, presumably
     /// causing Cargo to skip over this version.
     pub fn invalid_json(&mut self, invalid: bool) -> &mut Package {
@@ -375,6 +385,11 @@ impl Package {
         self
     }
 
+    pub fn cargo_feature(&mut self, feature: &str) -> &mut Package {
+        self.cargo_features.push(feature.to_owned());
+        self
+    }
+
     /// Creates the package and place it in the registry.
     ///
     /// This does not actually use Cargo's publishing system, but instead
@@ -502,15 +517,29 @@ impl Package {
     }
 
     fn append_manifest<W: Write>(&self, ar: &mut Builder<W>) {
-        let mut manifest = format!(
+        let mut manifest = String::new();
+
+        if !self.cargo_features.is_empty() {
+            manifest.push_str(&format!(
+                "cargo-features = {}\n\n",
+                toml::to_string(&self.cargo_features).unwrap()
+            ));
+        }
+
+        manifest.push_str(&format!(
             r#"
             [package]
             name = "{}"
             version = "{}"
             authors = []
         "#,
             self.name, self.vers
-        );
+        ));
+
+        if let Some(version) = &self.rust_version {
+            manifest.push_str(&format!("rust-version = \"{}\"", version));
+        }
+
         for dep in self.deps.iter() {
             let target = match dep.target {
                 None => String::new(),

src/bin/cargo/commands/bench.rs

@@ -39,6 +39,7 @@ pub fn cli() -> App {
         .arg_target_triple("Build for the target triple")
         .arg_target_dir()
         .arg_manifest_path()
+        .arg_ignore_rust_version()
         .arg_message_format()
         .arg(opt(
             "no-fail-fast",

src/bin/cargo/commands/build.rs

@@ -39,6 +39,7 @@ pub fn cli() -> App {
             .value_name("PATH"),
         )
         .arg_manifest_path()
+        .arg_ignore_rust_version()
         .arg_message_format()
         .arg_build_plan()
         .arg_unit_graph()

src/bin/cargo/commands/check.rs

@@ -32,6 +32,7 @@ pub fn cli() -> App {
         .arg_target_triple("Check for the target triple")
         .arg_target_dir()
         .arg_manifest_path()
+        .arg_ignore_rust_version()
         .arg_message_format()
         .arg_unit_graph()
         .after_help("Run `cargo help check` for more detailed information.\n")

src/bin/cargo/commands/doc.rs

@@ -30,6 +30,7 @@ pub fn cli() -> App {
         .arg_target_dir()
         .arg_manifest_path()
         .arg_message_format()
+        .arg_ignore_rust_version()
         .arg_unit_graph()
         .after_help("Run `cargo help doc` for more detailed information.\n")
 }

src/bin/cargo/commands/fix.rs

@@ -72,6 +72,7 @@ pub fn cli() -> App {
                 .long("allow-staged")
                 .help("Fix code even if the working directory has staged changes"),
         )
+        .arg_ignore_rust_version()
         .after_help("Run `cargo help fix` for more detailed information.\n")
 }
 

src/bin/cargo/commands/run.rs

@@ -26,6 +26,7 @@ pub fn cli() -> App {
         .arg_manifest_path()
         .arg_message_format()
         .arg_unit_graph()
+        .arg_ignore_rust_version()
         .after_help("Run `cargo help run` for more detailed information.\n")
 }
 

src/bin/cargo/commands/rustc.rs

@@ -30,6 +30,7 @@ pub fn cli() -> App {
         .arg_manifest_path()
         .arg_message_format()
         .arg_unit_graph()
+        .arg_ignore_rust_version()
         .after_help("Run `cargo help rustc` for more detailed information.\n")
 }
 

src/bin/cargo/commands/rustdoc.rs

@@ -34,6 +34,7 @@ pub fn cli() -> App {
         .arg_manifest_path()
         .arg_message_format()
         .arg_unit_graph()
+        .arg_ignore_rust_version()
         .after_help("Run `cargo help rustdoc` for more detailed information.\n")
 }