3 files changed, 70 insertions, 22 deletions

diff --git a/crates/project_model/src/lib.rs b/crates/project_model/src/lib.rs
index 724c586db..2d91939ce 100644
--- a/crates/project_model/src/lib.rs
+++ b/crates/project_model/src/lib.rs
@@ -39,11 +39,18 @@ pub enum ProjectWorkspace {
 impl fmt::Debug for ProjectWorkspace {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
-            ProjectWorkspace::Cargo { cargo, .. } => {
-                f.debug_struct("Cargo").field("n_packages", &cargo.packages().len()).finish()
-            }
+            ProjectWorkspace::Cargo { cargo, sysroot } => f
+                .debug_struct("Cargo")
+                .field("n_packages", &cargo.packages().len())
+                .field("n_sysroot_crates", &sysroot.crates().len())
+                .finish(),
             ProjectWorkspace::Json { project } => {
-                f.debug_struct("Json").field("n_crates", &project.n_crates()).finish()
+                let mut debug_struct = f.debug_struct("Json");
+                debug_struct.field("n_crates", &project.n_crates());
+                if let Some(sysroot) = &project.sysroot {
+                    debug_struct.field("n_sysroot_crates", &sysroot.crates().len());
+                }
+                debug_struct.finish()
             }
         }
     }
@@ -210,6 +217,13 @@ impl ProjectWorkspace {
                 })
                 .collect::<FxHashSet<_>>()
                 .into_iter()
+                .chain(project.sysroot.as_ref().into_iter().flat_map(|sysroot| {
+                    sysroot.crates().map(move |krate| PackageRoot {
+                        is_member: false,
+                        include: vec![sysroot[krate].root_dir().to_path_buf()],
+                        exclude: Vec::new(),
+                    })
+                }))
                 .collect::<Vec<_>>(),
             ProjectWorkspace::Cargo { cargo, sysroot } => cargo
                 .packages()
@@ -272,6 +286,11 @@ impl ProjectWorkspace {
         let mut crate_graph = CrateGraph::default();
         match self {
             ProjectWorkspace::Json { project } => {
+                let sysroot_dps = project
+                    .sysroot
+                    .as_ref()
+                    .map(|sysroot| sysroot_to_crate_graph(&mut crate_graph, sysroot, target, load));
+
                 let mut cfg_cache: FxHashMap<Option<&str>, Vec<CfgFlag>> = FxHashMap::default();
                 let crates: FxHashMap<_, _> = project
                     .crates()
@@ -309,25 +328,33 @@ impl ProjectWorkspace {
                     .collect();
 
                 for (from, krate) in project.crates() {
-                    for dep in &krate.deps {
-                        let to_crate_id = dep.crate_id;
-                        if let (Some(&from), Some(&to)) =
-                            (crates.get(&from), crates.get(&to_crate_id))
-                        {
-                            if let Err(_) = crate_graph.add_dep(from, dep.name.clone(), to) {
-                                log::error!("cyclic dependency {:?} -> {:?}", from, to_crate_id);
+                    if let Some(&from) = crates.get(&from) {
+                        if let Some((public_deps, _proc_macro)) = &sysroot_dps {
+                            for (name, to) in public_deps.iter() {
+                                if let Err(_) = crate_graph.add_dep(from, name.clone(), *to) {
+                                    log::error!("cyclic dependency on {} for {:?}", name, from)
+                                }
+                            }
+                        }
+
+                        for dep in &krate.deps {
+                            let to_crate_id = dep.crate_id;
+                            if let Some(&to) = crates.get(&to_crate_id) {
+                                if let Err(_) = crate_graph.add_dep(from, dep.name.clone(), to) {
+                                    log::error!("cyclic dependency {:?} -> {:?}", from, to);
+                                }
                             }
                         }
                     }
                 }
             }
             ProjectWorkspace::Cargo { cargo, sysroot } => {
+                let (public_deps, libproc_macro) =
+                    sysroot_to_crate_graph(&mut crate_graph, sysroot, target, load);
+
                 let mut cfg_options = CfgOptions::default();
                 cfg_options.extend(get_rustc_cfg_options(target));
 
-                let (public_deps, libproc_macro) =
-                    sysroot_to_crate_graph(&mut crate_graph, sysroot, &cfg_options, load);
-
                 let mut pkg_to_lib_crate = FxHashMap::default();
                 let mut pkg_crates = FxHashMap::default();
 
@@ -410,7 +437,11 @@ impl ProjectWorkspace {
                         }
                         for (name, krate) in public_deps.iter() {
                             if let Err(_) = crate_graph.add_dep(from, name.clone(), *krate) {
-                                log::error!("cyclic dependency on core for {}", &cargo[pkg].name)
+                                log::error!(
+                                    "cyclic dependency on {} for {}",
+                                    name,
+                                    &cargo[pkg].name
+                                )
                             }
                         }
                     }
@@ -485,9 +516,11 @@ fn utf8_stdout(mut cmd: Command) -> Result<String> {
 fn sysroot_to_crate_graph(
     crate_graph: &mut CrateGraph,
     sysroot: &Sysroot,
-    cfg_options: &CfgOptions,
+    target: Option<&str>,
     load: &mut dyn FnMut(&AbsPath) -> Option<FileId>,
 ) -> (Vec<(CrateName, CrateId)>, Option<CrateId>) {
+    let mut cfg_options = CfgOptions::default();
+    cfg_options.extend(get_rustc_cfg_options(target));
     let sysroot_crates: FxHashMap<_, _> = sysroot
         .crates()
         .filter_map(|krate| {
diff --git a/crates/project_model/src/project_json.rs b/crates/project_model/src/project_json.rs
index ae14e5126..5a0fe749a 100644
--- a/crates/project_model/src/project_json.rs
+++ b/crates/project_model/src/project_json.rs
@@ -7,11 +7,12 @@ use paths::{AbsPath, AbsPathBuf};
 use rustc_hash::FxHashMap;
 use serde::{de, Deserialize};
 
-use crate::cfg_flag::CfgFlag;
+use crate::{cfg_flag::CfgFlag, Sysroot};
 
 /// Roots and crates that compose this Rust project.
 #[derive(Clone, Debug, Eq, PartialEq)]
 pub struct ProjectJson {
+    pub(crate) sysroot: Option<Sysroot>,
     crates: Vec<Crate>,
 }
 
@@ -34,6 +35,7 @@ pub struct Crate {
 impl ProjectJson {
     pub fn new(base: &AbsPath, data: ProjectJsonData) -> ProjectJson {
         ProjectJson {
+            sysroot: data.sysroot_src.map(|it| base.join(it)).map(|it| Sysroot::load(&it)),
             crates: data
                 .crates
                 .into_iter()
@@ -43,11 +45,13 @@ impl ProjectJson {
                             && !crate_data.root_module.starts_with("..")
                             || crate_data.root_module.starts_with(base)
                     });
-                    let root_module = base.join(crate_data.root_module);
+                    let root_module = base.join(crate_data.root_module).normalize();
                     let (include, exclude) = match crate_data.source {
                         Some(src) => {
                             let absolutize = |dirs: Vec<PathBuf>| {
-                                dirs.into_iter().map(|it| base.join(it)).collect::<Vec<_>>()
+                                dirs.into_iter()
+                                    .map(|it| base.join(it).normalize())
+                                    .collect::<Vec<_>>()
                             };
                             (absolutize(src.include_dirs), absolutize(src.exclude_dirs))
                         }
@@ -89,6 +93,7 @@ impl ProjectJson {
 
 #[derive(Deserialize)]
 pub struct ProjectJsonData {
+    sysroot_src: Option<PathBuf>,
     crates: Vec<CrateData>,
 }
 
diff --git a/docs/user/manual.adoc b/docs/user/manual.adoc
index bebcee023..144130b51 100644
--- a/docs/user/manual.adoc
+++ b/docs/user/manual.adoc
@@ -273,9 +273,19 @@ However, if you use some other build system, you'll have to describe the structu
 [source,TypeScript]
 ----
 interface JsonProject {
-   /// The set of crates comprising the current project.
-   /// Must include all transitive dependencies as well as sysroot crate (libstd, libcore and such).
-   crates: Crate[];
+    /// Path to the directory with *source code* of sysroot crates.
+    ///
+    /// It should point to the directory where std, core, and friends can be found:
+    /// https://github.com/rust-lang/rust/tree/master/library.
+    ///
+    /// If provided, rust-analyzer automatically adds dependencies on sysroot
+    /// crates. Conversely, if you omit this path, you can specify sysroot
+    /// dependencies yourself and, for example, have several different "sysroots" in
+    /// one graph of crates.
+    sysroot_src?: string;
+    /// The set of crates comprising the current project.
+    /// Must include all transitive dependencies as well as sysroot crate (libstd, libcore and such).
+    crates: Crate[];
 }
 
 interface Crate {