Revert "feat(lints): Add unused deps ignore list"

This reverts commit b276acc.

This is a follow up to rust-lang#16935 where we take a different direction for
false positives.
Instead of an allowlist, we will ignore unused direct deps that are also
transitive deps (technically still used somewhere).
This leaves workflows like `curl` where the `build.rs` dynamically
decides what deps to use but that seems like enough of an exception case
to not worry about direct integration for.

Author: epage

src/cargo/core/compiler/unused_deps.rs

@@ -173,23 +173,6 @@ impl UnusedDepState {
                 continue;
             }
 
-            let mut ignore = Vec::new();
-            if let Some(unused_dependencies) = cargo_lints.get("unused_dependencies") {
-                if let Some(config) = unused_dependencies.config() {
-                    if let Some(config_ignore) = config.get("ignore") {
-                        if let Ok(config_ignore) =
-                            toml::Value::try_into::<Vec<InternedString>>(config_ignore.clone())
-                        {
-                            ignore = config_ignore
-                        } else {
-                            anyhow::bail!(
-                                "`lints.cargo.unused_dependencies.ignore` must be a list of string"
-                            );
-                        }
-                    }
-                }
-            }
-
             let manifest_path = rel_cwd_manifest_path(pkg.manifest_path(), build_runner.bcx.gctx);
             let mut lint_count = 0;
             for (dep_kind, state) in states.iter() {
@@ -249,15 +232,6 @@ impl UnusedDepState {
                         continue;
                     };
                     for dependency in dependency {
-                        if ignore.contains(&dependency.name_in_toml()) {
-                            debug!(
-                                "pkg {} v{} ({dep_kind:?}): ignoring unused extern `{ext}`, requested in manifest",
-                                pkg_id.name(),
-                                pkg_id.version(),
-                            );
-                            continue;
-                        }
-
                         let manifest = pkg.manifest();
                         let document = manifest.document();
                         let contents = manifest.contents();

src/cargo/lints/rules/unused_dependencies.rs

@@ -71,10 +71,6 @@ Should be written as:
 [package]
 name = "foo"
 ```
-
-### Configuration
-
-- `ignore`: a list of dependency names to allow the lint on
 "#,
     ),
 };
@@ -115,34 +111,13 @@ pub fn unused_build_dependencies_no_build_rs(
     let document = manifest.document();
     let contents = manifest.contents();
 
-    let mut ignore = Vec::new();
-    if let Some(unused_dependencies) = cargo_lints.get("unused_dependencies") {
-        if let Some(config) = unused_dependencies.config() {
-            if let Some(config_ignore) = config.get("ignore") {
-                if let Ok(config_ignore) =
-                    toml::Value::try_into::<Vec<String>>(config_ignore.clone())
-                {
-                    ignore = config_ignore
-                } else {
-                    anyhow::bail!(
-                        "`lints.cargo.unused_dependencies.ignore` must be a list of string"
-                    );
-                }
-            }
-        }
-    }
-
     for (i, dep_name) in manifest
         .normalized_toml()
         .build_dependencies()
         .iter()
         .flat_map(|m| m.keys())
         .enumerate()
     {
-        if ignore.contains(&dep_name) {
-            continue;
-        }
-
         let level = lint_level.to_diagnostic_level();
         let emitted_source = LINT.emitted_source(lint_level, reason);
 

src/cargo/util/toml/mod.rs

@@ -2734,7 +2734,6 @@ supported tools: {}",
 }
 
 static EXPECTED_LINT_CONFIG: &[(&str, &str, &str)] = &[
-    ("cargo", "unused_dependencies", "ignore"),
     // forwarded to rustc/rustdoc
     ("rust", "unexpected_cfgs", "check-cfg"),
 ];

src/doc/src/reference/lints.md

@@ -470,10 +470,6 @@ Should be written as:
 name = "foo"
 ```
 
-### Configuration
-
-- `ignore`: a list of dependency names to allow the lint on
-
 
 ## `unused_workspace_dependencies`
 Group: `suspicious`

tests/testsuite/lints/unused_dependencies.rs

@@ -1328,58 +1328,6 @@ pub fn fun() -> &'static str {
         .run();
 }
 
-#[cargo_test]
-fn config_ignore() {
-    // The most basic case where there is an unused dependency
-    Package::new("unused_build", "0.1.0").publish();
-    Package::new("unused", "0.1.0").publish();
-    let p = project()
-        .file(
-            "Cargo.toml",
-            r#"
-            [package]
-            name = "foo"
-            version = "0.1.0"
-            authors = []
-            edition = "2018"
-
-            [build-dependencies]
-            unused_build = "0.1.0"
-
-            [dependencies]
-            unused_renamed = { package = "unused", version = "0.1.0" }
-
-            [lints.cargo]
-            unused_dependencies = { level = "warn", ignore = ["unused_build", "unused_renamed"] }
-        "#,
-        )
-        .file(
-            "src/main.rs",
-            r#"
-            fn main() {}
-            "#,
-        )
-        .build();
-
-    p.cargo("check -Zcargo-lints")
-        .masquerade_as_nightly_cargo(&["cargo-lints"])
-        .with_stderr_data(
-            str![[r#"
-[UPDATING] `dummy-registry` index
-[LOCKING] 2 packages to latest compatible versions
-[DOWNLOADING] crates ...
-[DOWNLOADED] unused_build v0.1.0 (registry `dummy-registry`)
-[DOWNLOADED] unused v0.1.0 (registry `dummy-registry`)
-[CHECKING] unused v0.1.0
-[CHECKING] foo v0.1.0 ([ROOT]/foo)
-[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
-
-"#]]
-            .unordered(),
-        )
-        .run();
-}
-
 #[cargo_test]
 fn allow_rustflags() {
     // The most basic case where there is an unused dependency