feat(lints): Add redundant_homepage lint

src/cargo/core/workspace.rs

@@ -30,6 +30,7 @@ use crate::lints::rules::non_kebab_case_features;
 use crate::lints::rules::non_kebab_case_packages;
 use crate::lints::rules::non_snake_case_features;
 use crate::lints::rules::non_snake_case_packages;
+use crate::lints::rules::redundant_homepage;
 use crate::lints::rules::redundant_readme;
 use crate::ops;
 use crate::ops::lockfile::LOCKFILE_NAME;
@@ -1403,6 +1404,13 @@ impl<'gctx> Workspace<'gctx> {
                 &mut run_error_count,
                 self.gctx,
             )?;
+            redundant_homepage(
+                pkg.into(),
+                &path,
+                &cargo_lints,
+                &mut run_error_count,
+                self.gctx,
+            )?;
 
             if run_error_count > 0 {
                 let plural = if run_error_count == 1 { "" } else { "s" };

src/cargo/lints/rules/mod.rs

@@ -6,6 +6,7 @@ mod non_kebab_case_features;
 mod non_kebab_case_packages;
 mod non_snake_case_features;
 mod non_snake_case_packages;
+mod redundant_homepage;
 mod redundant_readme;
 mod unknown_lints;
 
@@ -17,6 +18,7 @@ pub use non_kebab_case_features::non_kebab_case_features;
 pub use non_kebab_case_packages::non_kebab_case_packages;
 pub use non_snake_case_features::non_snake_case_features;
 pub use non_snake_case_packages::non_snake_case_packages;
+pub use redundant_homepage::redundant_homepage;
 pub use redundant_readme::redundant_readme;
 pub use unknown_lints::output_unknown_lints;
 
@@ -29,6 +31,7 @@ pub const LINTS: &[crate::lints::Lint] = &[
     non_kebab_case_packages::LINT,
     non_snake_case_features::LINT,
     non_snake_case_packages::LINT,
+    redundant_homepage::LINT,
     redundant_readme::LINT,
     unknown_lints::LINT,
 ];

src/cargo/lints/rules/redundant_homepage.rs

@@ -0,0 +1,156 @@
+use std::path::Path;
+
+use annotate_snippets::AnnotationKind;
+use annotate_snippets::Group;
+use annotate_snippets::Level;
+use annotate_snippets::Origin;
+use annotate_snippets::Patch;
+use annotate_snippets::Snippet;
+use cargo_util_schemas::manifest::InheritableField;
+use cargo_util_schemas::manifest::TomlToolLints;
+
+use crate::CargoResult;
+use crate::GlobalContext;
+use crate::core::Package;
+use crate::lints::Lint;
+use crate::lints::LintLevel;
+use crate::lints::LintLevelReason;
+use crate::lints::STYLE;
+use crate::lints::get_key_value_span;
+use crate::lints::rel_cwd_manifest_path;
+
+pub const LINT: Lint = Lint {
+    name: "redundant_homepage",
+    desc: "`package.homepage` is redundant with another manifest field",
+    primary_group: &STYLE,
+    edition_lint_opts: None,
+    feature_gate: None,
+    docs: Some(
+        r#"
+### What it does
+
+Checks if the value of `package.homepage` is already covered by another field.
+
+See also [`package.homepage` reference documentation](manifest.md#the-homepage-field).
+
+### Why it is bad
+
+When package browsers render each link, a redundant link adds visual noise.
+
+### Drawbacks
+
+### Example
+
+```toml
+[package]
+name = "foo"
+homepage = "https://github.com/rust-lang/cargo/"
+repository = "https://github.com/rust-lang/cargo/"
+```
+
+Should be written as:
+
+```toml
+[package]
+name = "foo"
+repository = "https://github.com/rust-lang/cargo/"
+```
+"#,
+    ),
+};
+
+pub fn redundant_homepage(
+    pkg: &Package,
+    manifest_path: &Path,
+    cargo_lints: &TomlToolLints,
+    error_count: &mut usize,
+    gctx: &GlobalContext,
+) -> CargoResult<()> {
+    let (lint_level, reason) = LINT.level(
+        cargo_lints,
+        pkg.manifest().edition(),
+        pkg.manifest().unstable_features(),
+    );
+
+    if lint_level == LintLevel::Allow {
+        return Ok(());
+    }
+
+    let manifest_path = rel_cwd_manifest_path(manifest_path, gctx);
+
+    lint_package(pkg, &manifest_path, lint_level, reason, error_count, gctx)
+}
+
+pub fn lint_package(
+    pkg: &Package,
+    manifest_path: &str,
+    lint_level: LintLevel,
+    reason: LintLevelReason,
+    error_count: &mut usize,
+    gctx: &GlobalContext,
+) -> CargoResult<()> {
+    let manifest = pkg.manifest();
+
+    let Some(normalized_pkg) = &manifest.normalized_toml().package else {
+        return Ok(());
+    };
+    let Some(InheritableField::Value(homepage)) = &normalized_pkg.homepage else {
+        return Ok(());
+    };
+
+    let other_field = if let Some(InheritableField::Value(repository)) = &normalized_pkg.repository
+        && repository == homepage
+    {
+        "repository"
+    } else if let Some(InheritableField::Value(documentation)) = &normalized_pkg.documentation
+        && documentation == homepage
+    {
+        "documentation"
+    } else {
+        return Ok(());
+    };
+
+    let document = manifest.document();
+    let contents = manifest.contents();
+    let level = lint_level.to_diagnostic_level();
+    let emitted_source = LINT.emitted_source(lint_level, reason);
+
+    let mut primary = Group::with_title(level.primary_title(LINT.desc));
+    if let Some(document) = document
+        && let Some(contents) = contents
+        && let Some(span) = get_key_value_span(document, &["package", "homepage"])
+    {
+        let mut snippet = Snippet::source(contents)
+            .path(manifest_path)
+            .annotation(AnnotationKind::Primary.span(span.value));
+        if let Some(span) = get_key_value_span(document, &["package", other_field]) {
+            snippet = snippet.annotation(AnnotationKind::Context.span(span.value));
+        }
+        primary = primary.element(snippet);
+    } else {
+        primary = primary.element(Origin::path(manifest_path));
+    }
+    primary = primary.element(Level::NOTE.message(emitted_source));
+    let mut report = vec![primary];
+    if let Some(document) = document
+        && let Some(contents) = contents
+        && let Some(span) = get_key_value_span(document, &["package", "homepage"])
+    {
+        let mut help =
+            Group::with_title(Level::HELP.secondary_title("consider removing `package.homepage`"));
+        let span = span.key.start..span.value.end;
+        help = help.element(
+            Snippet::source(contents)
+                .path(manifest_path)
+                .patch(Patch::new(span, "")),
+        );
+        report.push(help);
+    }
+
+    if lint_level.is_error() {
+        *error_count += 1;
+    }
+    gctx.shell().print_report(&report, lint_level.force())?;
+
+    Ok(())
+}

src/doc/src/reference/lints.md

@@ -30,6 +30,7 @@ These lints are all set to the 'allow' level by default.
 These lints are all set to the 'warn' level by default.
 - [`blanket_hint_mostly_unused`](#blanket_hint_mostly_unused)
 - [`non_kebab_case_bins`](#non_kebab_case_bins)
+- [`redundant_homepage`](#redundant_homepage)
 - [`redundant_readme`](#redundant_readme)
 - [`unknown_lints`](#unknown_lints)
 
@@ -278,6 +279,41 @@ name = "foo-bar"
 ```
 
 
+## `redundant_homepage`
+Group: `style`
+
+Level: `warn`
+
+### What it does
+
+Checks if the value of `package.homepage` is already covered by another field.
+
+See also [`package.homepage` reference documentation](manifest.md#the-homepage-field).
+
+### Why it is bad
+
+When package browsers render each link, a redundant link adds visual noise.
+
+### Drawbacks
+
+### Example
+
+```toml
+[package]
+name = "foo"
+homepage = "https://github.com/rust-lang/cargo/"
+repository = "https://github.com/rust-lang/cargo/"
+```
+
+Should be written as:
+
+```toml
+[package]
+name = "foo"
+repository = "https://github.com/rust-lang/cargo/"
+```
+
+
 ## `redundant_readme`
 Group: `style`
 

tests/testsuite/lints/mod.rs

@@ -12,6 +12,7 @@ mod non_kebab_case_features;
 mod non_kebab_case_packages;
 mod non_snake_case_features;
 mod non_snake_case_packages;
+mod redundant_homepage;
 mod redundant_readme;
 mod unknown_lints;
 mod warning;

tests/testsuite/lints/redundant_homepage.rs

@@ -0,0 +1,91 @@
+use crate::prelude::*;
+use cargo_test_support::project;
+use cargo_test_support::str;
+
+#[cargo_test]
+fn with_repo() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+[package]
+name = "cargo"
+version = "0.0.1"
+edition = "2015"
+repository = "https://github.com/rust-lang/cargo/"
+homepage = "https://github.com/rust-lang/cargo/"
+
+[lints.cargo]
+redundant_homepage = "warn"
+"#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file("README.md", "")
+        .build();
+
+    p.cargo("check -Zcargo-lints")
+        .masquerade_as_nightly_cargo(&["cargo-lints"])
+        .with_stderr_data(str![[r#"
+[WARNING] `package.homepage` is redundant with another manifest field
+ --> Cargo.toml:7:12
+  |
+6 | repository = "https://github.com/rust-lang/cargo/"
+  |              -------------------------------------
+7 | homepage = "https://github.com/rust-lang/cargo/"
+  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = [NOTE] `cargo::redundant_homepage` is set to `warn` in `[lints]`
+[HELP] consider removing `package.homepage`
+  |
+7 - homepage = "https://github.com/rust-lang/cargo/"
+  |
+[CHECKING] cargo v0.0.1 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
+
+"#]])
+        .run();
+}
+
+#[cargo_test]
+fn with_docs() {
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+[package]
+name = "cargo"
+version = "0.0.1"
+edition = "2015"
+documentation = "https://docs.rs/cargo/latest/cargo/"
+homepage = "https://docs.rs/cargo/latest/cargo/"
+
+[lints.cargo]
+redundant_homepage = "warn"
+"#,
+        )
+        .file("src/main.rs", "fn main() {}")
+        .file("README.md", "")
+        .build();
+
+    p.cargo("check -Zcargo-lints")
+        .masquerade_as_nightly_cargo(&["cargo-lints"])
+        .with_stderr_data(str![[r#"
+[WARNING] `package.homepage` is redundant with another manifest field
+ --> Cargo.toml:7:12
+  |
+6 | documentation = "https://docs.rs/cargo/latest/cargo/"
+  |                 -------------------------------------
+7 | homepage = "https://docs.rs/cargo/latest/cargo/"
+  |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+  |
+  = [NOTE] `cargo::redundant_homepage` is set to `warn` in `[lints]`
+[HELP] consider removing `package.homepage`
+  |
+7 - homepage = "https://docs.rs/cargo/latest/cargo/"
+  |
+[CHECKING] cargo v0.0.1 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
+
+"#]])
+        .run();
+}