12 files changed, 237 insertions, 121 deletions

diff --git a/crates/project_model/src/build_data.rs b/crates/project_model/src/build_data.rs
index 0d4d39fef..ab5cc8c49 100644
--- a/crates/project_model/src/build_data.rs
+++ b/crates/project_model/src/build_data.rs
@@ -58,12 +58,17 @@ impl PartialEq for BuildDataConfig {
 
 impl Eq for BuildDataConfig {}
 
-#[derive(Debug, Default)]
+#[derive(Debug)]
 pub struct BuildDataCollector {
+    wrap_rustc: bool,
     configs: FxHashMap<AbsPathBuf, BuildDataConfig>,
 }
 
 impl BuildDataCollector {
+    pub fn new(wrap_rustc: bool) -> Self {
+        Self { wrap_rustc, configs: FxHashMap::default() }
+    }
+
     pub(crate) fn add_config(&mut self, workspace_root: &AbsPath, config: BuildDataConfig) {
         self.configs.insert(workspace_root.to_path_buf(), config);
     }
@@ -71,15 +76,14 @@ impl BuildDataCollector {
     pub fn collect(&mut self, progress: &dyn Fn(String)) -> Result<BuildDataResult> {
         let mut res = BuildDataResult::default();
         for (path, config) in self.configs.iter() {
-            res.per_workspace.insert(
-                path.clone(),
-                collect_from_workspace(
-                    &config.cargo_toml,
-                    &config.cargo_features,
-                    &config.packages,
-                    progress,
-                )?,
-            );
+            let workspace_build_data = WorkspaceBuildData::collect(
+                &config.cargo_toml,
+                &config.cargo_features,
+                &config.packages,
+                self.wrap_rustc,
+                progress,
+            )?;
+            res.per_workspace.insert(path.clone(), workspace_build_data);
         }
         Ok(res)
     }
@@ -120,119 +124,137 @@ impl BuildDataConfig {
     }
 }
 
-fn collect_from_workspace(
-    cargo_toml: &AbsPath,
-    cargo_features: &CargoConfig,
-    packages: &Vec<cargo_metadata::Package>,
-    progress: &dyn Fn(String),
-) -> Result<WorkspaceBuildData> {
-    let mut cmd = Command::new(toolchain::cargo());
-    cmd.args(&["check", "--workspace", "--message-format=json", "--manifest-path"])
-        .arg(cargo_toml.as_ref());
-
-    // --all-targets includes tests, benches and examples in addition to the
-    // default lib and bins. This is an independent concept from the --targets
-    // flag below.
-    cmd.arg("--all-targets");
-
-    if let Some(target) = &cargo_features.target {
-        cmd.args(&["--target", target]);
-    }
+impl WorkspaceBuildData {
+    fn collect(
+        cargo_toml: &AbsPath,
+        cargo_features: &CargoConfig,
+        packages: &Vec<cargo_metadata::Package>,
+        wrap_rustc: bool,
+        progress: &dyn Fn(String),
+    ) -> Result<WorkspaceBuildData> {
+        let mut cmd = Command::new(toolchain::cargo());
+
+        if wrap_rustc {
+            // Setup RUSTC_WRAPPER to point to `rust-analyzer` binary itself. We use
+            // that to compile only proc macros and build scripts during the initial
+            // `cargo check`.
+            let myself = std::env::current_exe()?;
+            cmd.env("RUSTC_WRAPPER", myself);
+            cmd.env("RA_RUSTC_WRAPPER", "1");
+        }
+
+        cmd.args(&["check", "--workspace", "--message-format=json", "--manifest-path"])
+            .arg(cargo_toml.as_ref());
 
-    if cargo_features.all_features {
-        cmd.arg("--all-features");
-    } else {
-        if cargo_features.no_default_features {
-            // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
-            // https://github.com/oli-obk/cargo_metadata/issues/79
-            cmd.arg("--no-default-features");
+        // --all-targets includes tests, benches and examples in addition to the
+        // default lib and bins. This is an independent concept from the --targets
+        // flag below.
+        cmd.arg("--all-targets");
+
+        if let Some(target) = &cargo_features.target {
+            cmd.args(&["--target", target]);
         }
-        if !cargo_features.features.is_empty() {
-            cmd.arg("--features");
-            cmd.arg(cargo_features.features.join(" "));
+
+        if cargo_features.all_features {
+            cmd.arg("--all-features");
+        } else {
+            if cargo_features.no_default_features {
+                // FIXME: `NoDefaultFeatures` is mutual exclusive with `SomeFeatures`
+                // https://github.com/oli-obk/cargo_metadata/issues/79
+                cmd.arg("--no-default-features");
+            }
+            if !cargo_features.features.is_empty() {
+                cmd.arg("--features");
+                cmd.arg(cargo_features.features.join(" "));
+            }
         }
-    }
 
-    cmd.stdout(Stdio::piped()).stderr(Stdio::piped()).stdin(Stdio::null());
-
-    let mut child = cmd.spawn().map(JodChild)?;
-    let child_stdout = child.stdout.take().unwrap();
-    let stdout = BufReader::new(child_stdout);
-
-    let mut res = WorkspaceBuildData::default();
-    for message in cargo_metadata::Message::parse_stream(stdout).flatten() {
-        match message {
-            Message::BuildScriptExecuted(BuildScript {
-                package_id, out_dir, cfgs, env, ..
-            }) => {
-                let cfgs = {
-                    let mut acc = Vec::new();
-                    for cfg in cfgs {
-                        match cfg.parse::<CfgFlag>() {
-                            Ok(it) => acc.push(it),
-                            Err(err) => {
-                                anyhow::bail!("invalid cfg from cargo-metadata: {}", err)
-                            }
-                        };
+        cmd.stdout(Stdio::piped()).stderr(Stdio::piped()).stdin(Stdio::null());
+
+        let mut child = cmd.spawn().map(JodChild)?;
+        let child_stdout = child.stdout.take().unwrap();
+        let stdout = BufReader::new(child_stdout);
+
+        let mut res = WorkspaceBuildData::default();
+        for message in cargo_metadata::Message::parse_stream(stdout).flatten() {
+            match message {
+                Message::BuildScriptExecuted(BuildScript {
+                    package_id,
+                    out_dir,
+                    cfgs,
+                    env,
+                    ..
+                }) => {
+                    let cfgs = {
+                        let mut acc = Vec::new();
+                        for cfg in cfgs {
+                            match cfg.parse::<CfgFlag>() {
+                                Ok(it) => acc.push(it),
+                                Err(err) => {
+                                    anyhow::bail!("invalid cfg from cargo-metadata: {}", err)
+                                }
+                            };
+                        }
+                        acc
+                    };
+                    let package_build_data =
+                        res.per_package.entry(package_id.repr.clone()).or_default();
+                    // cargo_metadata crate returns default (empty) path for
+                    // older cargos, which is not absolute, so work around that.
+                    if !out_dir.as_str().is_empty() {
+                        let out_dir = AbsPathBuf::assert(PathBuf::from(out_dir.into_os_string()));
+                        package_build_data.out_dir = Some(out_dir);
+                        package_build_data.cfgs = cfgs;
                     }
-                    acc
-                };
-                let package_build_data =
-                    res.per_package.entry(package_id.repr.clone()).or_default();
-                // cargo_metadata crate returns default (empty) path for
-                // older cargos, which is not absolute, so work around that.
-                if !out_dir.as_str().is_empty() {
-                    let out_dir = AbsPathBuf::assert(PathBuf::from(out_dir.into_os_string()));
-                    package_build_data.out_dir = Some(out_dir);
-                    package_build_data.cfgs = cfgs;
-                }
 
-                package_build_data.envs = env;
-            }
-            Message::CompilerArtifact(message) => {
-                progress(format!("metadata {}", message.target.name));
-
-                if message.target.kind.contains(&"proc-macro".to_string()) {
-                    let package_id = message.package_id;
-                    // Skip rmeta file
-                    if let Some(filename) = message.filenames.iter().find(|name| is_dylib(name)) {
-                        let filename = AbsPathBuf::assert(PathBuf::from(&filename));
-                        let package_build_data =
-                            res.per_package.entry(package_id.repr.clone()).or_default();
-                        package_build_data.proc_macro_dylib_path = Some(filename);
+                    package_build_data.envs = env;
+                }
+                Message::CompilerArtifact(message) => {
+                    progress(format!("metadata {}", message.target.name));
+
+                    if message.target.kind.contains(&"proc-macro".to_string()) {
+                        let package_id = message.package_id;
+                        // Skip rmeta file
+                        if let Some(filename) = message.filenames.iter().find(|name| is_dylib(name))
+                        {
+                            let filename = AbsPathBuf::assert(PathBuf::from(&filename));
+                            let package_build_data =
+                                res.per_package.entry(package_id.repr.clone()).or_default();
+                            package_build_data.proc_macro_dylib_path = Some(filename);
+                        }
                     }
                 }
+                Message::CompilerMessage(message) => {
+                    progress(message.target.name.clone());
+                }
+                Message::BuildFinished(_) => {}
+                Message::TextLine(_) => {}
+                _ => {}
             }
-            Message::CompilerMessage(message) => {
-                progress(message.target.name.clone());
-            }
-            Message::BuildFinished(_) => {}
-            Message::TextLine(_) => {}
-            _ => {}
         }
-    }
 
-    for package in packages {
-        let package_build_data = res.per_package.entry(package.id.repr.clone()).or_default();
-        inject_cargo_env(package, package_build_data);
-        if let Some(out_dir) = &package_build_data.out_dir {
-            // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
-            if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
-                package_build_data.envs.push(("OUT_DIR".to_string(), out_dir));
+        for package in packages {
+            let package_build_data = res.per_package.entry(package.id.repr.clone()).or_default();
+            inject_cargo_env(package, package_build_data);
+            if let Some(out_dir) = &package_build_data.out_dir {
+                // NOTE: cargo and rustc seem to hide non-UTF-8 strings from env! and option_env!()
+                if let Some(out_dir) = out_dir.to_str().map(|s| s.to_owned()) {
+                    package_build_data.envs.push(("OUT_DIR".to_string(), out_dir));
+                }
             }
         }
-    }
 
-    let output = child.into_inner().wait_with_output()?;
-    if !output.status.success() {
-        let mut stderr = String::from_utf8(output.stderr).unwrap_or_default();
-        if stderr.is_empty() {
-            stderr = "cargo check failed".to_string();
+        let output = child.into_inner().wait_with_output()?;
+        if !output.status.success() {
+            let mut stderr = String::from_utf8(output.stderr).unwrap_or_default();
+            if stderr.is_empty() {
+                stderr = "cargo check failed".to_string();
+            }
+            res.error = Some(stderr)
         }
-        res.error = Some(stderr)
-    }
 
-    Ok(res)
+        Ok(res)
+    }
 }
 
 // FIXME: File a better way to know if it is a dylib
diff --git a/crates/rust-analyzer/src/benchmarks.rs b/crates/rust-analyzer/src/benchmarks.rs
index bf569b40b..bdd94b1c4 100644
--- a/crates/rust-analyzer/src/benchmarks.rs
+++ b/crates/rust-analyzer/src/benchmarks.rs
@@ -30,8 +30,11 @@ fn benchmark_integrated_highlighting() {
     let file = "./crates/ide_db/src/apply_change.rs";
 
     let cargo_config = Default::default();
-    let load_cargo_config =
-        LoadCargoConfig { load_out_dirs_from_check: true, with_proc_macro: false };
+    let load_cargo_config = LoadCargoConfig {
+        load_out_dirs_from_check: true,
+        wrap_rustc: false,
+        with_proc_macro: false,
+    };
 
     let (mut host, vfs, _proc_macro) = {
         let _it = stdx::timeit("workspace loading");
diff --git a/crates/rust-analyzer/src/bin/main.rs b/crates/rust-analyzer/src/bin/main.rs
index 873e82c7b..f0abb5b15 100644
--- a/crates/rust-analyzer/src/bin/main.rs
+++ b/crates/rust-analyzer/src/bin/main.rs
@@ -3,6 +3,7 @@
 //! Based on cli flags, either spawns an LSP server, or runs a batch analysis
 mod flags;
 mod logger;
+mod rustc_wrapper;
 
 use std::{convert::TryFrom, env, fs, path::Path, process};
 
@@ -26,6 +27,20 @@ static ALLOC: mimalloc::MiMalloc = mimalloc::MiMalloc;
 static ALLOC: jemallocator::Jemalloc = jemallocator::Jemalloc;
 
 fn main() {
+    if std::env::var("RA_RUSTC_WRAPPER").is_ok() {
+        let mut args = std::env::args_os();
+        let _me = args.next().unwrap();
+        let rustc = args.next().unwrap();
+        let code = match rustc_wrapper::run_rustc_skipping_cargo_checking(rustc, args.collect()) {
+            Ok(rustc_wrapper::ExitCode(code)) => code.unwrap_or(102),
+            Err(err) => {
+                eprintln!("{}", err);
+                101
+            }
+        };
+        process::exit(code);
+    }
+
     if let Err(err) = try_main() {
         log::error!("Unexpected error: {}", err);
         eprintln!("{}", err);
diff --git a/crates/rust-analyzer/src/bin/rustc_wrapper.rs b/crates/rust-analyzer/src/bin/rustc_wrapper.rs
new file mode 100644
index 000000000..2f6d4706d
--- /dev/null
+++ b/crates/rust-analyzer/src/bin/rustc_wrapper.rs
@@ -0,0 +1,46 @@
+//! We setup RUSTC_WRAPPER to point to `rust-analyzer` binary itself during the
+//! initial `cargo check`. That way, we avoid checking the actual project, and
+//! only build proc macros and build.rs.
+//!
+//! Code taken from IntelliJ :0)
+//!     https://github.com/intellij-rust/intellij-rust/blob/master/native-helper/src/main.rs
+use std::{
+    ffi::OsString,
+    io,
+    process::{Command, Stdio},
+};
+
+/// ExitCode/ExitStatus are impossible to create :(.
+pub(crate) struct ExitCode(pub(crate) Option<i32>);
+
+pub(crate) fn run_rustc_skipping_cargo_checking(
+    rustc_executable: OsString,
+    args: Vec<OsString>,
+) -> io::Result<ExitCode> {
+    let is_cargo_check = args.iter().any(|arg| {
+        let arg = arg.to_string_lossy();
+        // `cargo check` invokes `rustc` with `--emit=metadata` argument.
+        //
+        // https://doc.rust-lang.org/rustc/command-line-arguments.html#--emit-specifies-the-types-of-output-files-to-generate
+        // link —     Generates the crates specified by --crate-type. The default
+        //            output filenames depend on the crate type and platform. This
+        //            is the default if --emit is not specified.
+        // metadata — Generates a file containing metadata about the crate.
+        //            The default output filename is CRATE_NAME.rmeta.
+        arg.starts_with("--emit=") && arg.contains("metadata") && !arg.contains("link")
+    });
+    if is_cargo_check {
+        return Ok(ExitCode(Some(0)));
+    }
+    run_rustc(rustc_executable, args)
+}
+
+fn run_rustc(rustc_executable: OsString, args: Vec<OsString>) -> io::Result<ExitCode> {
+    let mut child = Command::new(rustc_executable)
+        .args(args)
+        .stdin(Stdio::inherit())
+        .stdout(Stdio::inherit())
+        .stderr(Stdio::inherit())
+        .spawn()?;
+    Ok(ExitCode(child.wait()?.code()))
+}
diff --git a/crates/rust-analyzer/src/cli/analysis_stats.rs b/crates/rust-analyzer/src/cli/analysis_stats.rs
index fe9f273b0..3f3134562 100644
--- a/crates/rust-analyzer/src/cli/analysis_stats.rs
+++ b/crates/rust-analyzer/src/cli/analysis_stats.rs
@@ -68,6 +68,7 @@ impl AnalysisStatsCmd {
         cargo_config.no_sysroot = self.no_sysroot;
         let load_cargo_config = LoadCargoConfig {
             load_out_dirs_from_check: self.load_output_dirs,
+            wrap_rustc: false,
             with_proc_macro: self.with_proc_macro,
         };
         let (host, vfs, _proc_macro) =
diff --git a/crates/rust-analyzer/src/cli/diagnostics.rs b/crates/rust-analyzer/src/cli/diagnostics.rs
index 8b985716b..0085d0e4d 100644
--- a/crates/rust-analyzer/src/cli/diagnostics.rs
+++ b/crates/rust-analyzer/src/cli/diagnostics.rs
@@ -34,7 +34,8 @@ pub fn diagnostics(
     with_proc_macro: bool,
 ) -> Result<()> {
     let cargo_config = Default::default();
-    let load_cargo_config = LoadCargoConfig { load_out_dirs_from_check, with_proc_macro };
+    let load_cargo_config =
+        LoadCargoConfig { load_out_dirs_from_check, with_proc_macro, wrap_rustc: false };
     let (host, _vfs, _proc_macro) =
         load_workspace_at(path, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
diff --git a/crates/rust-analyzer/src/cli/load_cargo.rs b/crates/rust-analyzer/src/cli/load_cargo.rs
index 310c36904..75bad1112 100644
--- a/crates/rust-analyzer/src/cli/load_cargo.rs
+++ b/crates/rust-analyzer/src/cli/load_cargo.rs
@@ -15,6 +15,7 @@ use crate::reload::{ProjectFolders, SourceRootConfig};
 
 pub struct LoadCargoConfig {
     pub load_out_dirs_from_check: bool,
+    pub wrap_rustc: bool,
     pub with_proc_macro: bool,
 }
 
@@ -52,7 +53,7 @@ pub fn load_workspace(
     };
 
     let build_data = if config.load_out_dirs_from_check {
-        let mut collector = BuildDataCollector::default();
+        let mut collector = BuildDataCollector::new(config.wrap_rustc);
         ws.collect_build_data_configs(&mut collector);
         Some(collector.collect(progress)?)
     } else {
@@ -136,8 +137,11 @@ mod tests {
     fn test_loading_rust_analyzer() -> Result<()> {
         let path = Path::new(env!("CARGO_MANIFEST_DIR")).parent().unwrap().parent().unwrap();
         let cargo_config = Default::default();
-        let load_cargo_config =
-            LoadCargoConfig { load_out_dirs_from_check: false, with_proc_macro: false };
+        let load_cargo_config = LoadCargoConfig {
+            load_out_dirs_from_check: false,
+            wrap_rustc: false,
+            with_proc_macro: false,
+        };
         let (host, _vfs, _proc_macro) =
             load_workspace_at(path, &cargo_config, &load_cargo_config, &|_| {})?;
 
diff --git a/crates/rust-analyzer/src/cli/ssr.rs b/crates/rust-analyzer/src/cli/ssr.rs
index 79f426fff..1fd9b5a9b 100644
--- a/crates/rust-analyzer/src/cli/ssr.rs
+++ b/crates/rust-analyzer/src/cli/ssr.rs
@@ -9,8 +9,11 @@ use ide_ssr::{MatchFinder, SsrPattern, SsrRule};
 pub fn apply_ssr_rules(rules: Vec<SsrRule>) -> Result<()> {
     use ide_db::base_db::SourceDatabaseExt;
     let cargo_config = Default::default();
-    let load_cargo_config =
-        LoadCargoConfig { load_out_dirs_from_check: true, with_proc_macro: true };
+    let load_cargo_config = LoadCargoConfig {
+        load_out_dirs_from_check: true,
+        wrap_rustc: false,
+        with_proc_macro: true,
+    };
     let (host, vfs, _proc_macro) =
         load_workspace_at(&std::env::current_dir()?, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
@@ -37,7 +40,7 @@ pub fn search_for_patterns(patterns: Vec<SsrPattern>, debug_snippet: Option<Stri
     use ide_db::symbol_index::SymbolsDatabase;
     let cargo_config = Default::default();
     let load_cargo_config =
-        LoadCargoConfig { load_out_dirs_from_check: true, with_proc_macro: true };
+        LoadCargoConfig { load_out_dirs_from_check: true, wrap_rustc: true, with_proc_macro: true };
     let (host, _vfs, _proc_macro) =
         load_workspace_at(&std::env::current_dir()?, &cargo_config, &load_cargo_config, &|_| {})?;
     let db = host.raw_database();
diff --git a/crates/rust-analyzer/src/config.rs b/crates/rust-analyzer/src/config.rs
index f809667e9..1edaa394a 100644
--- a/crates/rust-analyzer/src/config.rs
+++ b/crates/rust-analyzer/src/config.rs
@@ -48,6 +48,9 @@ config_data! {
         /// Run build scripts (`build.rs`) for more precise code analysis.
         cargo_runBuildScripts |
         cargo_loadOutDirsFromCheck: bool = "true",
+        /// Use `RUSTC_WRAPPER=rust-analyzer` when running build scripts to
+        /// avoid compiling unnecessary things.
+        cargo_useRustcWrapperForBuildScripts: bool = "true",
         /// Do not activate the `default` feature.
         cargo_noDefaultFeatures: bool    = "false",
         /// Compilation target (target triple).
@@ -493,6 +496,9 @@ impl Config {
     pub fn run_build_scripts(&self) -> bool {
         self.data.cargo_runBuildScripts || self.data.procMacro_enable
     }
+    pub fn wrap_rustc(&self) -> bool {
+        self.data.cargo_useRustcWrapperForBuildScripts
+    }
     pub fn cargo(&self) -> CargoConfig {
         let rustc_source = self.data.rustcSource.as_ref().map(|rustc_src| {
             if rustc_src == "discover" {
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index 47c6c6d77..b3d4c6ec5 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -236,7 +236,8 @@ impl GlobalState {
                                     let workspaces_updated = !Arc::ptr_eq(&old, &self.workspaces);
 
                                     if self.config.run_build_scripts() && workspaces_updated {
-                                        let mut collector = BuildDataCollector::default();
+                                        let mut collector =
+                                            BuildDataCollector::new(self.config.wrap_rustc());
                                         for ws in self.workspaces.iter() {
                                             ws.collect_build_data_configs(&mut collector);
                                         }
diff --git a/crates/rust-analyzer/tests/rust-analyzer/main.rs b/crates/rust-analyzer/tests/rust-analyzer/main.rs
index 4442cbff6..1e4c04bbf 100644
--- a/crates/rust-analyzer/tests/rust-analyzer/main.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/main.rs
@@ -527,7 +527,7 @@ version = \"0.0.0\"
 #[test]
 fn out_dirs_check() {
     if skip_slow_tests() {
-        return;
+        // return;
     }
 
     let server = Project::with_fixture(
diff --git a/crates/rust-analyzer/tests/rust-analyzer/support.rs b/crates/rust-analyzer/tests/rust-analyzer/support.rs
index 8d68f1b7d..5e388c0f0 100644
--- a/crates/rust-analyzer/tests/rust-analyzer/support.rs
+++ b/crates/rust-analyzer/tests/rust-analyzer/support.rs
@@ -32,8 +32,12 @@ impl<'a> Project<'a> {
             tmp_dir: None,
             roots: vec![],
             config: serde_json::json!({
-                // Loading standard library is costly, let's ignore it by default
-                "cargo": { "noSysroot": true }
+                "cargo": {
+                    // Loading standard library is costly, let's ignore it by default
+                    "noSysroot": true,
+                    // Can't use test binary as rustc wrapper.
+                    "useRustcWrapperForBuildScripts": false,
+                }
             }),
         }
     }
@@ -49,7 +53,17 @@ impl<'a> Project<'a> {
     }
 
     pub(crate) fn with_config(mut self, config: serde_json::Value) -> Project<'a> {
-        self.config = config;
+        fn merge(dst: &mut serde_json::Value, src: serde_json::Value) {
+            match (dst, src) {
+                (Value::Object(dst), Value::Object(src)) => {
+                    for (k, v) in src {
+                        merge(dst.entry(k).or_insert(v.clone()), v)
+                    }
+                }
+                (dst, src) => *dst = src,
+            }
+        }
+        merge(&mut self.config, config);
         self
     }