Respect [lints.rust.unexpected_cfgs.check-cfg] lint config

src/cargo/core/compiler/build_context/target_info.rs

@@ -364,6 +364,45 @@ impl TargetInfo {
         true
     }
 
+    /// The [`CheckCfg`] settings with extra arguments passed.
+    pub fn check_cfg_with_extra_args(
+        &self,
+        gctx: &GlobalContext,
+        rustc: &Rustc,
+        extra_args: &[String],
+    ) -> CargoResult<CheckCfg> {
+        let mut process = rustc.workspace_process();
+
+        apply_env_config(gctx, &mut process)?;
+        process
+            .arg("-")
+            .arg("--print=check-cfg")
+            .arg("--check-cfg=cfg()")
+            .arg("-Zunstable-options")
+            .args(&self.rustflags)
+            .args(extra_args)
+            .env_remove("RUSTC_LOG");
+
+        // Removes `FD_CLOEXEC` set by `jobserver::Client` to pass jobserver
+        // as environment variables specify.
+        if let Some(client) = gctx.jobserver_from_env() {
+            process.inherit_jobserver(client);
+        }
+
+        let (output, _error) = rustc
+            .cached_output(&process, 0)
+            .with_context(|| "failed to run `rustc` to learn about check-cfg information")?;
+
+        let lines = output.lines();
+        let mut check_cfg = CheckCfg::default();
+        check_cfg.exhaustive = true;
+
+        Ok(lines.fold(check_cfg, |mut check_cfg, line| {
+            check_cfg.process_line(line);
+            check_cfg
+        }))
+    }
+
     /// All the target [`Cfg`] settings.
     pub fn cfg(&self) -> &[Cfg] {
         &self.cfg

src/cargo/util/lints.rs

@@ -976,6 +976,20 @@ pub fn unexpected_target_cfgs(
         return Ok(());
     };
 
+    // If we have extra `--check-cfg` args comming from the lints config, we need to
+    // refetch the `--print=check-cfg` with those extra args.
+    let lint_rustflags = pkg.manifest().lint_rustflags();
+    let check_cfg = if lint_rustflags.iter().any(|a| a == "--check-cfg") {
+        Some(target_info.check_cfg_with_extra_args(gctx, &rustc, lint_rustflags)?)
+    } else {
+        None
+    };
+    let check_cfg = check_cfg.as_ref().unwrap_or(&global_check_cfg);
+
+    if !check_cfg.exhaustive {
+        return Ok(());
+    }
+
     for dep in pkg.summary().dependencies() {
         let Some(platform) = dep.platform() else {
             continue;
@@ -984,16 +998,9 @@ pub fn unexpected_target_cfgs(
             continue;
         };
 
-        // FIXME: If the `[lints.rust.unexpected_cfgs.check-cfg]` config is set we should
-        // re-fetch the check-cfg informations with those extra args
-
-        if !global_check_cfg.exhaustive {
-            continue;
-        }
-
         warn_on_unexpected_cfgs(
             gctx,
-            &global_check_cfg,
+            &check_cfg,
             cfg_expr,
             lint_level,
             error_count,

src/doc/src/reference/unstable.md

@@ -1735,8 +1735,6 @@ When in doubt, you can discuss this in [#14520](https://github.com/rust-lang/car
 
 * Tracking Issue: [#00000](https://github.com/rust-lang/cargo/issues/00000)
 
-**WARNING: Incomplete/WIP!**
-
 This feature checks for unexpected cfgs in `[target.'cfg(...)']` entries, based
 on `rustc --print=check-cfg`.
 

tests/testsuite/cfg.rs

@@ -620,11 +620,8 @@ fn unexpected_cfgs_target_with_lint() {
 
     p.cargo("check -Zcargo-lints -Zcheck-target-cfgs")
         .masquerade_as_nightly_cargo(&["requires -Zcheck-target-cfgs"])
-        // FIXME: We should not warn on `cfg(foo = "foo")` but we currently do
         .with_stderr_data(str![[r#"
 [WARNING] [ROOT]/foo/Cargo.toml: unexpected `cfg` condition name: `bar` in `[target.'cfg(bar)'.dependencies]`
-[WARNING] [ROOT]/foo/Cargo.toml: unexpected `cfg` condition name: `foo` for `foo = "foo"` in `[target.'cfg(foo = "foo")'.dependencies]`
-[WARNING] [ROOT]/foo/Cargo.toml: unexpected `cfg` condition name: `foo` in `[target.'cfg(foo)'.dependencies]`
 [LOCKING] 1 package to latest compatible version
 [CHECKING] a v0.0.1 ([ROOT]/foo)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
@@ -729,13 +726,12 @@ fn unexpected_cfgs_target_cfg_any() {
 
     p.cargo("check -Zcargo-lints -Zcheck-target-cfgs")
         .masquerade_as_nightly_cargo(&["requires -Zcheck-target-cfgs"])
-        // FIXME: We shouldn't be linting `cfg(foo)` because of the `cfg(any())`
         .with_stderr_data(str![[r#"
-[ERROR] [ROOT]/foo/Cargo.toml: unexpected `cfg` condition name: `foo` in `[target.'cfg(foo)'.dependencies]`
+[LOCKING] 1 package to latest compatible version
+[CHECKING] a v0.0.1 ([ROOT]/foo)
+[FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s
 
 "#]])
-        // nor should we error out because of the level="deny"
-        .with_status(101)
         .run();
 }