feat: Add unstable im_a_teapot lint

src/cargo/core/workspace.rs

@@ -24,7 +24,7 @@ use crate::sources::{PathSource, CRATES_IO_INDEX, CRATES_IO_REGISTRY};
 use crate::util::edit_distance;
 use crate::util::errors::{CargoResult, ManifestError};
 use crate::util::interning::InternedString;
-use crate::util::lints::{check_implicit_features, unused_dependencies};
+use crate::util::lints::{check_im_a_teapot, check_implicit_features, unused_dependencies};
 use crate::util::toml::{read_manifest, InheritableFields};
 use crate::util::{
     context::CargoResolverConfig, context::CargoResolverPrecedence, context::ConfigRelativePath,
@@ -1206,6 +1206,7 @@ impl<'gctx> Workspace<'gctx> {
             .map(|(name, lint)| (name.replace('-', "_"), lint))
             .collect();
 
+        check_im_a_teapot(pkg, &path, &normalized_lints, &mut error_count, self.gctx)?;
         check_implicit_features(pkg, &path, &normalized_lints, &mut error_count, self.gctx)?;
         unused_dependencies(pkg, &path, &normalized_lints, &mut error_count, self.gctx)?;
         if error_count > 0 {

src/cargo/util/lints.rs

@@ -142,6 +142,61 @@ impl From<TomlLintLevel> for LintLevel {
     }
 }
 
+const IM_A_TEAPOT: Lint = Lint {
+    name: "im_a_teapot",
+    desc: "`im_a_teapot` is specified",
+    groups: &[],
+    default_level: LintLevel::Allow,
+    edition_lint_opts: None,
+};
+
+pub fn check_im_a_teapot(
+    pkg: &Package,
+    path: &Path,
+    lints: &TomlToolLints,
+    error_count: &mut usize,
+    gctx: &GlobalContext,
+) -> CargoResult<()> {
+    let manifest = pkg.manifest();
+    let lint_level = IM_A_TEAPOT.level(lints, manifest.edition());
+    if lint_level == LintLevel::Allow {
+        return Ok(());
+    }
+
+    if manifest
+        .resolved_toml()
+        .package()
+        .is_some_and(|p| p.im_a_teapot.is_some())
+    {
+        if lint_level == LintLevel::Forbid || lint_level == LintLevel::Deny {
+            *error_count += 1;
+        }
+        let level = lint_level.to_diagnostic_level();
+        let manifest_path = rel_cwd_manifest_path(path, gctx);
+        let emitted_reason = format!("`cargo::{}` is set to `{lint_level}`", IM_A_TEAPOT.name);
+
+        let key_span = get_span(manifest.document(), &["package", "im-a-teapot"], false).unwrap();
+        let value_span = get_span(manifest.document(), &["package", "im-a-teapot"], true).unwrap();
+        let message = level
+            .title(IM_A_TEAPOT.desc)
+            .snippet(
+                Snippet::source(manifest.contents())
+                    .origin(&manifest_path)
+                    .annotation(level.span(key_span.start..value_span.end))
+                    .fold(true),
+            )
+            .footer(Level::Note.title(&emitted_reason));
+        let renderer = Renderer::styled().term_width(
+            gctx.shell()
+                .err_width()
+                .diagnostic_terminal_width()
+                .unwrap_or(annotate_snippets::renderer::DEFAULT_TERM_WIDTH),
+        );
+        writeln!(gctx.shell().err(), "{}", renderer.render(message))?;
+    }
+    Ok(())
+}
+
 /// By default, cargo will treat any optional dependency as a [feature]. As of
 /// cargo 1.60, these can be disabled by declaring a feature that activates the
 /// optional dependency as `dep:<name>` (see [RFC #3143]).

tests/testsuite/lints_table.rs

@@ -756,14 +756,14 @@ fn cargo_lints_nightly_required() {
         .file(
             "Cargo.toml",
             r#"
-                [package]
-                name = "foo"
-                version = "0.0.1"
-                edition = "2015"
-                authors = []
-
-                [lints.cargo]
-                "unused-features" = "deny"
+[package]
+name = "foo"
+version = "0.0.1"
+edition = "2015"
+authors = []
+
+[lints.cargo]
+im-a-teapot = "warn"
             "#,
         )
         .file("src/lib.rs", "")
@@ -790,21 +790,24 @@ fn cargo_lints_no_z_flag() {
         .file(
             "Cargo.toml",
             r#"
-                [package]
-                name = "foo"
-                version = "0.0.1"
-                edition = "2015"
-                authors = []
+cargo-features = ["test-dummy-unstable"]
+
+[package]
+name = "foo"
+version = "0.0.1"
+edition = "2015"
+authors = []
+im-a-teapot = true
 
-                [lints.cargo]
-                "unused-features" = "deny"
+[lints.cargo]
+im-a-teapot = "warn"
             "#,
         )
         .file("src/lib.rs", "")
         .build();
 
     foo.cargo("check")
-        .masquerade_as_nightly_cargo(&["-Zcargo-lints"])
+        .masquerade_as_nightly_cargo(&["cargo-lints", "test-dummy-unstable"])
         .with_stderr(
             "\
 [WARNING] unused manifest key `lints.cargo` (may be supported in a future version)
@@ -819,27 +822,37 @@ consider passing `-Zcargo-lints` to enable this feature.
 
 #[cargo_test]
 fn cargo_lints_success() {
-    let foo = project()
+    let p = project()
         .file(
             "Cargo.toml",
             r#"
-                [package]
-                name = "foo"
-                version = "0.0.1"
-                edition = "2015"
-                authors = []
+cargo-features = ["test-dummy-unstable"]
+
+[package]
+name = "foo"
+version = "0.0.1"
+edition = "2015"
+authors = []
+im-a-teapot = true
 
-                [lints.cargo]
-                "unused-features" = "deny"
+[lints.cargo]
+im-a-teapot = "warn"
             "#,
         )
         .file("src/lib.rs", "")
         .build();
 
-    foo.cargo("check -Zcargo-lints")
-        .masquerade_as_nightly_cargo(&["-Zcargo-lints"])
+    p.cargo("check -Zcargo-lints")
+        .masquerade_as_nightly_cargo(&["cargo-lints", "test-dummy-unstable"])
         .with_stderr(
             "\
+warning: `im_a_teapot` is specified
+ --> Cargo.toml:9:1
+  |
+9 | im-a-teapot = true
+  | ------------------
+  |
+  = note: `cargo::im_a_teapot` is set to `warn`
 [CHECKING] foo v0.0.1 ([CWD])
 [FINISHED] [..]
 ",
@@ -849,40 +862,37 @@ fn cargo_lints_success() {
 
 #[cargo_test]
 fn cargo_lints_underscore_supported() {
-    Package::new("bar", "0.1.0").publish();
     let foo = project()
         .file(
             "Cargo.toml",
             r#"
-                [package]
-                name = "foo"
-                version = "0.0.1"
-                edition = "2021"
-                authors = []
+cargo-features = ["test-dummy-unstable"]
 
-                [lints.cargo]
-                "implicit_features" = "warn"
+[package]
+name = "foo"
+version = "0.0.1"
+edition = "2015"
+authors = []
+im-a-teapot = true
 
-                [dependencies]
-                bar = { version = "0.1.0", optional = true }
+[lints.cargo]
+im_a_teapot = "warn"
             "#,
         )
         .file("src/lib.rs", "")
         .build();
 
     foo.cargo("check -Zcargo-lints")
-        .masquerade_as_nightly_cargo(&["-Zcargo-lints"])
+        .masquerade_as_nightly_cargo(&["cargo-lints", "test-dummy-unstable"])
         .with_stderr(
             "\
-warning: implicit features for optional dependencies is deprecated and will be unavailable in the 2024 edition
-  --> Cargo.toml:12:17
-   |
-12 |                 bar = { version = \"0.1.0\", optional = true }
-   |                 ---
-   |
-   = note: `cargo::implicit_features` is set to `warn`
-[UPDATING] `dummy-registry` index
-[LOCKING] [..]
+warning: `im_a_teapot` is specified
+ --> Cargo.toml:9:1
+  |
+9 | im-a-teapot = true
+  | ------------------
+  |
+  = note: `cargo::im_a_teapot` is set to `warn`
 [CHECKING] foo v0.0.1 ([CWD])
 [FINISHED] [..]
 ",