feat: Add lint to detect missing rust-version field

CHANGELOG.md

@@ -5828,6 +5828,7 @@ Released 2018-09-13
 [`missing_fields_in_debug`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_fields_in_debug
 [`missing_inline_in_public_items`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_inline_in_public_items
 [`missing_panics_doc`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_panics_doc
+[`missing_rust_version`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_rust_version
 [`missing_safety_doc`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_safety_doc
 [`missing_spin_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_spin_loop
 [`missing_trait_methods`]: https://rust-lang.github.io/rust-clippy/master/index.html#missing_trait_methods

clippy_lints/src/cargo/missing_rust_version.rs

@@ -0,0 +1,21 @@
+use cargo_metadata::Metadata;
+use clippy_utils::diagnostics::span_lint;
+use clippy_utils::msrvs::{self, Msrv};
+use rustc_lint::LateContext;
+use rustc_span::DUMMY_SP;
+
+use super::MISSING_RUST_VERSION;
+
+pub(super) fn check(cx: &LateContext<'_>, metadata: &Metadata, msrv: &Msrv) {
+    // see <https://github.com/oli-obk/cargo_metadata/issues/253>
+    if !msrv.meets(msrvs::RUST_VERSION_FIELD) {
+        return;
+    }
+
+    for package in &metadata.packages {
+        if package.rust_version.is_none() {
+            let message = format!("package `{}` is missing the `rust-version` field", package.name);
+            span_lint(cx, MISSING_RUST_VERSION, DUMMY_SP, message);
+        }
+    }
+}

clippy_lints/src/cargo/mod.rs

@@ -1,13 +1,15 @@
 mod common_metadata;
 mod feature_name;
 mod lint_groups_priority;
+mod missing_rust_version;
 mod multiple_crate_versions;
 mod wildcard_dependencies;
 
 use cargo_metadata::MetadataCommand;
 use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint;
 use clippy_utils::is_lint_allowed;
+use clippy_utils::msrvs::Msrv;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::hir_id::CRATE_HIR_ID;
 use rustc_lint::{LateContext, LateLintPass, Lint};
@@ -213,9 +215,37 @@ declare_clippy_lint! {
     "a lint group in `Cargo.toml` at the same priority as a lint"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks to see if the `rust-version` field is defined in `Cargo.toml`.
+    ///
+    /// ### Why is this bad?
+    /// Starting with version 3, the [resolver] takes this field into account
+    /// when picking dependencies.
+    ///
+    /// ### Example
+    /// ```toml
+    /// [package]
+    /// # ...
+    /// ```
+    /// Use instead:
+    /// ```toml
+    /// [package]
+    /// # ...
+    /// rust-version = "1.84"
+    /// ```
+    ///
+    /// [resolver]: https://doc.rust-lang.org/cargo/reference/resolver.html#rust-version
+    #[clippy::version = "1.86.0"]
+    pub MISSING_RUST_VERSION,
+    cargo,
+    "the `rust-version` field is not defined in `Cargo.toml`"
+}
+
 pub struct Cargo {
     allowed_duplicate_crates: FxHashSet<String>,
     ignore_publish: bool,
+    msrv: Msrv,
 }
 
 impl_lint_pass!(Cargo => [
@@ -225,13 +255,15 @@ impl_lint_pass!(Cargo => [
     MULTIPLE_CRATE_VERSIONS,
     WILDCARD_DEPENDENCIES,
     LINT_GROUPS_PRIORITY,
+    MISSING_RUST_VERSION,
 ]);
 
 impl Cargo {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
             allowed_duplicate_crates: conf.allowed_duplicate_crates.iter().cloned().collect(),
             ignore_publish: conf.cargo_ignore_publish,
+            msrv: conf.msrv.clone(),
         }
     }
 }
@@ -243,6 +275,7 @@ impl LateLintPass<'_> for Cargo {
             REDUNDANT_FEATURE_NAMES,
             NEGATIVE_FEATURE_NAMES,
             WILDCARD_DEPENDENCIES,
+            MISSING_RUST_VERSION,
         ];
         static WITH_DEPS_LINTS: &[&Lint] = &[MULTIPLE_CRATE_VERSIONS];
 
@@ -256,6 +289,7 @@ impl LateLintPass<'_> for Cargo {
                 Ok(metadata) => {
                     common_metadata::check(cx, &metadata, self.ignore_publish);
                     feature_name::check(cx, &metadata);
+                    missing_rust_version::check(cx, &metadata, &self.msrv);
                     wildcard_dependencies::check(cx, &metadata);
                 },
                 Err(e) => {
@@ -282,4 +316,6 @@ impl LateLintPass<'_> for Cargo {
             }
         }
     }
+
+    extract_msrv_attr!(LateContext);
 }

clippy_lints/src/declared_lints.rs

@@ -72,6 +72,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::byte_char_slices::BYTE_CHAR_SLICES_INFO,
     crate::cargo::CARGO_COMMON_METADATA_INFO,
     crate::cargo::LINT_GROUPS_PRIORITY_INFO,
+    crate::cargo::MISSING_RUST_VERSION_INFO,
     crate::cargo::MULTIPLE_CRATE_VERSIONS_INFO,
     crate::cargo::NEGATIVE_FEATURE_NAMES_INFO,
     crate::cargo::REDUNDANT_FEATURE_NAMES_INFO,

clippy_utils/src/msrvs.rs

@@ -33,7 +33,7 @@ msrv_aliases! {
     1,63,0 { CLONE_INTO }
     1,62,0 { BOOL_THEN_SOME, DEFAULT_ENUM_ATTRIBUTE, CONST_EXTERN_C_FN }
     1,59,0 { THREAD_LOCAL_CONST_INIT }
-    1,58,0 { FORMAT_ARGS_CAPTURE, PATTERN_TRAIT_CHAR_ARRAY, CONST_RAW_PTR_DEREF }
+    1,58,0 { FORMAT_ARGS_CAPTURE, PATTERN_TRAIT_CHAR_ARRAY, CONST_RAW_PTR_DEREF, RUST_VERSION_FIELD }
     1,56,0 { CONST_FN_UNION }
     1,55,0 { SEEK_REWIND }
     1,54,0 { INTO_KEYS }

tests/ui-cargo/missing_rust_version/fail/Cargo.stderr

@@ -0,0 +1,6 @@
+error: package `missing_rust_version` is missing the `rust-version` field
+  |
+  = note: `-D clippy::missing-rust-version` implied by `-D warnings`
+  = help: to override `-D warnings` add `#[allow(clippy::missing_rust_version)]`
+
+error: could not compile `missing_rust_version` (bin "missing_rust_version") due to 1 previous error

tests/ui-cargo/missing_rust_version/fail/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "missing_rust_version"
+version = "0.1.0"
+publish = false
+
+[workspace]

tests/ui-cargo/missing_rust_version/fail/src/main.rs

@@ -0,0 +1,3 @@
+#![warn(clippy::missing_rust_version)]
+
+fn main() {}

tests/ui-cargo/missing_rust_version/pass/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "missing_rust_version"
+version = "0.1.0"
+rust-version = "1.84"
+publish = false
+
+[workspace]

tests/ui-cargo/missing_rust_version/pass/src/main.rs

@@ -0,0 +1,3 @@
+#![warn(clippy::missing_rust_version)]
+
+fn main() {}