fix: forward build.warnings config to external subcommands

src/bin/cargo/main.rs

@@ -1,4 +1,5 @@
 use cargo::core::features;
+use cargo::util::context::WarningHandling;
 use cargo::util::network::http::http_handle;
 use cargo::util::network::http::needs_custom_http_transport;
 use cargo::util::{self, CargoResult, closest_msg, command_prelude};
@@ -315,6 +316,11 @@ fn execute_subcommand(
         None => ProcessBuilder::new(&cargo_exe),
     };
     cmd.env(cargo::CARGO_ENV, cargo_exe).args(args);
+    if let Ok(handling) = gctx.warning_handling() {
+        if handling != WarningHandling::Warn {
+            cmd.env("CARGO_BUILD_WARNINGS", handling.as_str());
+        }
+    }
     if let Some(client) = gctx.jobserver_from_env() {
         cmd.inherit_jobserver(client);
     }

src/cargo/util/context/schema.rs

@@ -237,6 +237,16 @@ pub enum WarningHandling {
     Deny,
 }
 
+impl WarningHandling {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            WarningHandling::Warn => "warn",
+            WarningHandling::Allow => "allow",
+            WarningHandling::Deny => "deny",
+        }
+    }
+}
+
 /// Configuration for `build.target`.
 ///
 /// Accepts in the following forms:

tests/testsuite/warning_override.rs

@@ -527,3 +527,51 @@ fn cap_lints_allow() {
 "#]])
         .run();
 }
+
+#[cargo_test]
+fn config_before_subcommand_forwarded() {
+    let clippy_mock = project()
+        .at("cargo-clippy-mock")
+        .file(
+            "Cargo.toml",
+            &cargo_test_support::basic_manifest("cargo-clippy-mock", "0.0.1"),
+        )
+        .file(
+            "src/main.rs",
+            r#"
+                fn main() {
+                    let cargo = std::env::var("CARGO").unwrap_or_else(|_| "cargo".to_string());
+                    let mut cmd = std::process::Command::new(cargo);
+                    cmd.arg("check");
+                    cmd.args(std::env::args().skip(2));
+                    let status = cmd.status().unwrap();
+                    std::process::exit(status.code().unwrap_or(1));
+                }
+            "#,
+        )
+        .build();
+    clippy_mock.cargo("build").run();
+
+    let p = make_project_with_rustc_warning();
+
+    let mut path =
+        std::env::split_paths(&std::env::var_os("PATH").unwrap_or_default()).collect::<Vec<_>>();
+    path.push(clippy_mock.target_debug_dir());
+    let path = std::env::join_paths(path.iter()).unwrap();
+
+    p.cargo("")
+        .arg("--config")
+        .arg("build.warnings='deny'")
+        .arg("clippy-mock")
+        .env("PATH", &path)
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+[CHECKING] foo v0.0.1 ([ROOT]/foo)
+[WARNING] unused variable: `x`
+...
+[ERROR] `foo` (bin "foo") generated 1 warning (run `cargo fix --bin "foo" -p foo` to apply 1 suggestion)
+[ERROR] warnings are denied by `build.warnings` configuration
+
+"#]])
+        .run();
+}