fix(lints): Only warn when seeing lints on stable

This will make it easier for users to test this feature

src/cargo/util/toml/mod.rs

@@ -2045,8 +2045,8 @@ impl TomlManifest {
                 let mut inheritable = toml_config.package.clone().unwrap_or_default();
                 inheritable.update_ws_path(package_root.to_path_buf());
                 inheritable.update_deps(toml_config.dependencies.clone());
-                verify_lints(toml_config.lints.as_ref(), &features)?;
-                inheritable.update_lints(toml_config.lints.clone());
+                let lints = verify_lints(toml_config.lints.clone(), &features, config)?;
+                inheritable.update_lints(lints);
                 if let Some(ws_deps) = &inheritable.dependencies {
                     for (name, dep) in ws_deps {
                         unused_dep_keys(
@@ -2315,7 +2315,7 @@ impl TomlManifest {
             .clone()
             .map(|mw| mw.resolve("lints", || inherit()?.lints()))
             .transpose()?;
-        verify_lints(lints.as_ref(), &features)?;
+        let lints = verify_lints(lints.clone(), &features, config)?;
         let default = TomlLints::default();
         let mut rustflags = lints
             .as_ref()
@@ -2773,8 +2773,8 @@ impl TomlManifest {
                 let mut inheritable = toml_config.package.clone().unwrap_or_default();
                 inheritable.update_ws_path(root.to_path_buf());
                 inheritable.update_deps(toml_config.dependencies.clone());
-                verify_lints(toml_config.lints.as_ref(), &features)?;
-                inheritable.update_lints(toml_config.lints.clone());
+                let lints = verify_lints(toml_config.lints.clone(), &features, config)?;
+                inheritable.update_lints(lints);
                 let ws_root_config = WorkspaceRootConfig::new(
                     root,
                     &toml_config.members,
@@ -2919,12 +2919,19 @@ impl TomlManifest {
     }
 }
 
-fn verify_lints(lints: Option<&TomlLints>, features: &Features) -> CargoResult<()> {
-    let Some(lints) = lints else { return Ok(()); };
+fn verify_lints(
+    lints: Option<TomlLints>,
+    features: &Features,
+    config: &Config,
+) -> CargoResult<Option<TomlLints>> {
+    let Some(lints) = lints else { return Ok(None); };
 
-    features.require(Feature::lints())?;
+    if let Err(err) = features.require(Feature::lints()) {
+        let _ = config.shell().warn(err);
+        return Ok(None);
+    }
 
-    for (tool, lints) in lints {
+    for (tool, lints) in &lints {
         let supported = ["rust", "clippy", "rustdoc"];
         if !supported.contains(&tool.as_str()) {
             let supported = supported.join(", ");
@@ -2947,7 +2954,7 @@ fn verify_lints(lints: Option<&TomlLints>, features: &Features) -> CargoResult<(
         }
     }
 
-    Ok(())
+    Ok(Some(lints))
 }
 
 fn unused_dep_keys(

tests/testsuite/lints.rs

@@ -22,16 +22,15 @@ fn package_requires_option() {
         .build();
 
     foo.cargo("check")
-        .with_status(101)
         .with_stderr("\
-[..]
+warning: feature `lints` is required
 
-Caused by:
-  feature `lints` is required
+The package requires the Cargo feature called `lints`, but that feature is not stabilized in this version of Cargo ([..]).
+Consider trying a newer version of Cargo (this may require the nightly release).
+See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#lints for more information about the status of this feature.
 
-  The package requires the Cargo feature called `lints`, but that feature is not stabilized in this version of Cargo ([..]).
-  Consider trying a newer version of Cargo (this may require the nightly release).
-  See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#lints for more information about the status of this feature.
+[CHECKING] [..]
+[FINISHED] [..]
 ")
         .run();
 }
@@ -55,16 +54,15 @@ fn workspace_requires_option() {
         .build();
 
     foo.cargo("check")
-        .with_status(101)
         .with_stderr("\
-[..]
+warning: feature `lints` is required
 
-Caused by:
-  feature `lints` is required
+The package requires the Cargo feature called `lints`, but that feature is not stabilized in this version of Cargo ([..]).
+Consider trying a newer version of Cargo (this may require the nightly release).
+See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#lints for more information about the status of this feature.
 
-  The package requires the Cargo feature called `lints`, but that feature is not stabilized in this version of Cargo ([..]).
-  Consider trying a newer version of Cargo (this may require the nightly release).
-  See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#lints for more information about the status of this feature.
+[CHECKING] [..]
+[FINISHED] [..]
 ")
         .run();
 }
@@ -333,7 +331,6 @@ pub fn foo(num: i32) -> u32 {
 
     foo.cargo("check")
         .masquerade_as_nightly_cargo(&["lints"])
-        .with_status(0)
         .run();
 }
 
@@ -368,7 +365,6 @@ pub fn foo(num: i32) -> u32 {
         .arg("-v")
         .env("RUSTFLAGS", "-Aunsafe_code")
         .masquerade_as_nightly_cargo(&["lints"])
-        .with_status(0)
         .run();
 }
 
@@ -457,7 +453,6 @@ pub fn foo() -> u32 {
 
     foo.cargo("check")
         .masquerade_as_nightly_cargo(&["lints"])
-        .with_status(0)
         .run();
 }