Add option to only run build scripts and compile proc macros

src/bin/cargo/commands/check.rs

@@ -36,6 +36,7 @@ pub fn cli() -> App {
         .arg_message_format()
         .arg_unit_graph()
         .arg_future_incompat_report()
+        .arg_only_build_scripts_and_proc_macros()
         .after_help("Run `cargo help check` for more detailed information.\n")
 }
 

src/cargo/core/compiler/build_config.rs

@@ -26,6 +26,11 @@ pub struct BuildConfig {
     pub build_plan: bool,
     /// Output the unit graph to stdout instead of actually compiling.
     pub unit_graph: bool,
+    /// Only for `cargo check`.
+    /// Skips actual check and only compile proc macros and run build script.
+    /// This is needed for IDEs.
+    /// See https://github.com/rust-lang/cargo/issues/7178 for details.
+    pub only_build_scripts_and_proc_macros: bool,
     /// An optional override of the rustc process for primary units
     pub primary_unit_rustc: Option<ProcessBuilder>,
     /// A thread used by `cargo fix` to receive messages on a socket regarding
@@ -79,6 +84,7 @@ impl BuildConfig {
             force_rebuild: false,
             build_plan: false,
             unit_graph: false,
+            only_build_scripts_and_proc_macros: false,
             primary_unit_rustc: None,
             rustfix_diagnostic_server: RefCell::new(None),
             export_dir: None,

src/cargo/core/compiler/mod.rs

@@ -147,6 +147,7 @@ fn compile<'cfg>(
 ) -> CargoResult<()> {
     let bcx = cx.bcx;
     let build_plan = bcx.build_config.build_plan;
+    let only_build_scripts_and_proc_macros = bcx.build_config.only_build_scripts_and_proc_macros;
     if !cx.compiled.insert(unit.clone()) {
         return Ok(());
     }
@@ -163,6 +164,8 @@ fn compile<'cfg>(
         Job::new_fresh()
     } else if build_plan {
         Job::new_dirty(rustc(cx, unit, &exec.clone())?)
+    } else if only_build_scripts_and_proc_macros && matches!(unit.mode, CompileMode::Check { .. }) {
+        Job::new_fresh()
     } else {
         let force = exec.force_rebuild(unit) || force_rebuild;
         let mut job = fingerprint::prepare_target(cx, unit, force)?;

src/cargo/util/command_prelude.rs

@@ -172,6 +172,11 @@ pub trait AppExt: Sized {
         self._arg(opt("unit-graph", "Output build graph in JSON (unstable)"))
     }
 
+    fn arg_only_build_scripts_and_proc_macros(self) -> Self {
+        let help = "Skip actual check and only run build scripts and compile proc macros";
+        self._arg(opt("only-build-scripts-and-proc-macros", help).hidden(true))
+    }
+
     fn arg_new_opts(self) -> Self {
         self._arg(
             opt(
@@ -470,6 +475,8 @@ pub trait ArgMatchesExt {
         build_config.build_plan = self._is_present("build-plan");
         build_config.unit_graph = self._is_present("unit-graph");
         build_config.future_incompat_report = self._is_present("future-incompat-report");
+        build_config.only_build_scripts_and_proc_macros =
+            self._is_present("only-build-scripts-and-proc-macros");
         if build_config.build_plan {
             config
                 .cli_unstable()
@@ -492,6 +499,11 @@ pub trait ArgMatchesExt {
                 )
             }
         }
+        if build_config.only_build_scripts_and_proc_macros {
+            config
+                .cli_unstable()
+                .fail_if_stable_opt("--only-build-scripts-and-proc-macros", 7178)?;
+        }
 
         let opts = CompileOptions {
             build_config,

tests/testsuite/main.rs

@@ -81,6 +81,7 @@ mod net_config;
 mod new;
 mod offline;
 mod old_cargos;
+mod only_build_scripts_and_proc_macros;
 mod out_dir;
 mod owner;
 mod package;

tests/testsuite/only_build_scripts_and_proc_macros.rs

@@ -0,0 +1,33 @@
+//! Tests for --only-build-scripts-and-proc-macros feature.
+
+use cargo_test_support::{basic_bin_manifest, project};
+
+#[cargo_test]
+fn simple_build_script() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file("src/foo.rs", "fn main() {}")
+        .file(
+            "build.rs",
+            r#"fn main() { println!("cargo:rustc-cfg=my_feature"); }"#,
+        )
+        .build();
+
+    p.cargo("check -Zunstable-options --only-build-scripts-and-proc-macros --message-format json")
+        .masquerade_as_nightly_cargo()
+        .with_stdout_contains("[..]my_feature[..]")
+        .run();
+}
+
+#[cargo_test]
+fn main_code_not_checked() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file("src/foo.rs", "some invalid code")
+        .build();
+
+    p.cargo("check -Zunstable-options --only-build-scripts-and-proc-macros")
+        .masquerade_as_nightly_cargo()
+        .run();
+    assert!(!p.bin("foo").is_file());
+}