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

Author: Urgau

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

@@ -411,6 +411,47 @@ 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;
+
+        for line in lines {
+            check_cfg
+                .parse_print_check_cfg_line(line)
+                .with_context(|| format!("unable to parse a line from `--print=check-cfg`"))?;
+        }
+        Ok(check_cfg)
+    }
+
     /// All the target [`Cfg`] settings.
     pub fn cfg(&self) -> &[Cfg] {
         &self.cfg

src/cargo/util/lints.rs

@@ -665,13 +665,20 @@ pub fn unexpected_target_cfgs(
         return Ok(());
     };
 
-    if !global_check_cfg.exhaustive {
+    // 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(());
     }
 
-    // FIXME: If the `[lints.rust.unexpected_cfgs.check-cfg]` config is set we should
-    // re-fetch the check-cfg informations with those extra args
-
     for dep in pkg.summary().dependencies() {
         let Some(platform) = dep.platform() else {
             continue;
@@ -686,7 +693,7 @@ pub fn unexpected_target_cfgs(
                 Cfg::KeyPair(name, value) => (name, Some(value.to_string())),
             };
 
-            match global_check_cfg.expecteds.get(name.as_str()) {
+            match check_cfg.expecteds.get(name.as_str()) {
                 Some(ExpectedValues::Some(values)) if !values.contains(&value) => {
                     let level = lint_level.to_diagnostic_level();
                     if lint_level == LintLevel::Forbid || lint_level == LintLevel::Deny {

tests/testsuite/cfg.rs

@@ -941,26 +941,13 @@ 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] unexpected `cfg` condition name: bar
   --> Cargo.toml:14:25
    |
 14 |                 [target."cfg(bar)".dependencies]
    |                         ----------
    |
-[WARNING] unexpected `cfg` condition name: foo for `foo = "foo"`
-  --> Cargo.toml:11:25
-   |
-11 |                 [target.'cfg(foo = "foo")'.dependencies] # should not warn here
-   |                         ------------------
-   |
-[WARNING] unexpected `cfg` condition name: foo
- --> Cargo.toml:8:25
-  |
-8 |                 [target."cfg(foo)".dependencies] # should not warn here
-  |                         ----------
-  |
 [LOCKING] 1 package to latest compatible version
 [CHECKING] a v0.0.1 ([ROOT]/foo)
 [FINISHED] `dev` profile [unoptimized + debuginfo] target(s) in [ELAPSED]s