diff --git a/Cargo.lock b/Cargo.lock
index 4551ffc44e7..4b89e36d176 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1089,6 +1089,8 @@ dependencies = [
  "ra_arena 0.1.0",
  "ra_db 0.1.0",
  "rustc-hash 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.89 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_json 1.0.39 (registry+https://github.com/rust-lang/crates.io-index)",
  "test_utils 0.1.0",
  "walkdir 2.2.7 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
diff --git a/crates/ra_batch/src/lib.rs b/crates/ra_batch/src/lib.rs
index 89a234f4c34..2db0380632d 100644
--- a/crates/ra_batch/src/lib.rs
+++ b/crates/ra_batch/src/lib.rs
@@ -99,12 +99,7 @@ pub fn load_cargo(root: impl AsRef<Path>) -> Result<(BatchDatabase, Vec<SourceRo
         let ws = ProjectWorkspace::discover(root.as_ref())?;
         let mut roots = Vec::new();
         roots.push(root.clone());
-        for pkg in ws.cargo.packages() {
-            roots.push(pkg.root(&ws.cargo).to_path_buf());
-        }
-        for krate in ws.sysroot.crates() {
-            roots.push(krate.root_dir(&ws.sysroot).to_path_buf())
-        }
+        ws.add_roots(&mut roots);
         let (mut vfs, roots) = Vfs::new(roots);
         let mut load = |path: &Path| {
             let vfs_file = vfs.load(path);
diff --git a/crates/ra_lsp_server/src/cargo_target_spec.rs b/crates/ra_lsp_server/src/cargo_target_spec.rs
index e011eab7cb0..cdf2ec10b66 100644
--- a/crates/ra_lsp_server/src/cargo_target_spec.rs
+++ b/crates/ra_lsp_server/src/cargo_target_spec.rs
@@ -1,5 +1,5 @@
 use crate::{
-    project_model::TargetKind,
+    project_model::{self, TargetKind},
     server_world::ServerWorld,
     Result
 };
@@ -65,14 +65,16 @@ pub fn for_file(world: &ServerWorld, file_id: FileId) -> Result<Option<CargoTarg
         };
         let file_id = world.analysis().crate_root(crate_id)?;
         let path = world.vfs.read().file2path(ra_vfs::VfsFile(file_id.0.into()));
-        let res = world.workspaces.iter().find_map(|ws| {
-            let tgt = ws.cargo.target_by_root(&path)?;
-            let res = CargoTargetSpec {
-                package: tgt.package(&ws.cargo).name(&ws.cargo).to_string(),
-                target: tgt.name(&ws.cargo).to_string(),
-                target_kind: tgt.kind(&ws.cargo),
-            };
-            Some(res)
+        let res = world.workspaces.iter().find_map(|ws| match ws {
+            project_model::ProjectWorkspace::Cargo { cargo, .. } => {
+                let tgt = cargo.target_by_root(&path)?;
+                Some(CargoTargetSpec {
+                    package: tgt.package(&cargo).name(&cargo).to_string(),
+                    target: tgt.name(&cargo).to_string(),
+                    target_kind: tgt.kind(&cargo),
+                })
+            }
+            project_model::ProjectWorkspace::Json { .. } => None,
         });
         Ok(res)
     }
diff --git a/crates/ra_lsp_server/src/server_world.rs b/crates/ra_lsp_server/src/server_world.rs
index 4a68c019ff4..4625a26a71b 100644
--- a/crates/ra_lsp_server/src/server_world.rs
+++ b/crates/ra_lsp_server/src/server_world.rs
@@ -40,12 +40,7 @@ pub fn new(root: PathBuf, workspaces: Vec<ProjectWorkspace>) -> ServerWorldState
         let mut roots = Vec::new();
         roots.push(root.clone());
         for ws in workspaces.iter() {
-            for pkg in ws.cargo.packages() {
-                roots.push(pkg.root(&ws.cargo).to_path_buf());
-            }
-            for krate in ws.sysroot.crates() {
-                roots.push(krate.root_dir(&ws.sysroot).to_path_buf())
-            }
+            ws.add_roots(&mut roots);
         }
         let (mut vfs, roots) = Vfs::new(roots);
         let roots_to_scan = roots.len();
@@ -185,7 +180,7 @@ pub fn status(&self) -> String {
         } else {
             res.push_str("workspaces:\n");
             for w in self.workspaces.iter() {
-                res += &format!("{} packages loaded\n", w.cargo.packages().count());
+                res += &format!("{} packages loaded\n", w.count());
             }
         }
         res.push_str("\nanalysis:\n");
diff --git a/crates/ra_lsp_server/tests/heavy_tests/main.rs b/crates/ra_lsp_server/tests/heavy_tests/main.rs
index 1c099a78f59..641f84cfc94 100644
--- a/crates/ra_lsp_server/tests/heavy_tests/main.rs
+++ b/crates/ra_lsp_server/tests/heavy_tests/main.rs
@@ -12,8 +12,9 @@
     CodeActionParams, CodeActionRequest, Formatting, Runnables, RunnablesParams, CompletionParams, Completion,
 };
 use serde_json::json;
+use tempfile::TempDir;
 
-use crate::support::project;
+use crate::support::{project, project_with_tmpdir};
 
 const LOG: &'static str = "";
 
@@ -258,3 +259,65 @@ fn main() {}
         json!([]),
     );
 }
+
+#[test]
+fn test_missing_module_code_action_in_json_project() {
+    let tmp_dir = TempDir::new().unwrap();
+    let code = format!(
+        r#"
+//- rust-project.json
+{{ 
+    "roots": [ "{PATH}" ], 
+    "crates": [ {{ "root_module": "{PATH}/src/lib.rs", "deps": [], "edition": "2015" }} ] 
+}}
+
+//- src/lib.rs
+mod bar;
+
+fn main() {}
+"#,
+        PATH = tmp_dir.path().display()
+    );
+    let server = project_with_tmpdir(tmp_dir, &code);
+    server.wait_for_feedback("workspace loaded");
+    let empty_context = || CodeActionContext { diagnostics: Vec::new(), only: None };
+    server.request::<CodeActionRequest>(
+        CodeActionParams {
+            text_document: server.doc_id("src/lib.rs"),
+            range: Range::new(Position::new(0, 4), Position::new(0, 7)),
+            context: empty_context(),
+        },
+        json!([
+          {
+            "command": {
+              "arguments": [
+                {
+                  "cursorPosition": null,
+                  "label": "create module",
+                  "workspaceEdit": {
+                    "documentChanges": [
+                      {
+                        "kind": "create",
+                        "uri": "file:///[..]/src/bar.rs"
+                      }
+                    ]
+                  }
+                }
+              ],
+              "command": "rust-analyzer.applySourceChange",
+              "title": "create module"
+            },
+            "title": "create module"
+          }
+        ]),
+    );
+
+    server.request::<CodeActionRequest>(
+        CodeActionParams {
+            text_document: server.doc_id("src/lib.rs"),
+            range: Range::new(Position::new(2, 4), Position::new(2, 7)),
+            context: empty_context(),
+        },
+        json!([]),
+    );
+}
diff --git a/crates/ra_lsp_server/tests/heavy_tests/support.rs b/crates/ra_lsp_server/tests/heavy_tests/support.rs
index 8bfc8d62206..e02d7858ec8 100644
--- a/crates/ra_lsp_server/tests/heavy_tests/support.rs
+++ b/crates/ra_lsp_server/tests/heavy_tests/support.rs
@@ -27,12 +27,16 @@
 };
 
 pub fn project(fixture: &str) -> Server {
+    let tmp_dir = TempDir::new().unwrap();
+    project_with_tmpdir(tmp_dir, fixture)
+}
+
+pub fn project_with_tmpdir(tmp_dir: TempDir, fixture: &str) -> Server {
     static INIT: Once = Once::new();
     INIT.call_once(|| {
         let _ = Logger::with_env_or_str(crate::LOG).start().unwrap();
     });
 
-    let tmp_dir = TempDir::new().unwrap();
     let mut paths = vec![];
 
     for entry in parse_fixture(fixture) {
diff --git a/crates/ra_project_model/Cargo.toml b/crates/ra_project_model/Cargo.toml
index 262406e99cc..487cdfaf117 100644
--- a/crates/ra_project_model/Cargo.toml
+++ b/crates/ra_project_model/Cargo.toml
@@ -17,5 +17,8 @@ cargo_metadata = "0.7.0"
 ra_arena = { path = "../ra_arena" }
 ra_db = { path = "../ra_db" }
 
+serde = "1.0.89"
+serde_json = "1.0.39"
+
 [dev-dependencies]
 test_utils = { path = "../test_utils" }
diff --git a/crates/ra_project_model/src/json_project.rs b/crates/ra_project_model/src/json_project.rs
new file mode 100644
index 00000000000..9a9eb9e1fde
--- /dev/null
+++ b/crates/ra_project_model/src/json_project.rs
@@ -0,0 +1,49 @@
+use std::path::PathBuf;
+
+use serde::Deserialize;
+
+/// A root points to the directory which contains Rust crates. rust-analyzer watches all files in
+/// all roots. Roots might be nested.
+#[derive(Clone, Debug, Deserialize)]
+#[serde(transparent)]
+pub struct Root {
+    pub(crate) path: PathBuf,
+}
+
+/// A crate points to the root module of a crate and lists the dependencies of the crate. This is
+/// useful in creating the crate graph.
+#[derive(Clone, Debug, Deserialize)]
+pub struct Crate {
+    pub(crate) root_module: PathBuf,
+    pub(crate) edition: Edition,
+    pub(crate) deps: Vec<Dep>,
+}
+
+#[derive(Clone, Copy, Debug, Deserialize)]
+#[serde(rename = "edition")]
+pub enum Edition {
+    #[serde(rename = "2015")]
+    Edition2015,
+    #[serde(rename = "2018")]
+    Edition2018,
+}
+
+/// Identifies a crate by position in the crates array.
+#[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, Ord, PartialEq, PartialOrd)]
+#[serde(transparent)]
+pub struct CrateId(pub usize);
+
+/// A dependency of a crate, identified by its id in the crates array and name.
+#[derive(Clone, Debug, Deserialize)]
+pub struct Dep {
+    #[serde(rename = "crate")]
+    pub(crate) krate: CrateId,
+    pub(crate) name: String,
+}
+
+/// Roots and crates that compose this Rust project.
+#[derive(Clone, Debug, Deserialize)]
+pub struct JsonProject {
+    pub(crate) roots: Vec<Root>,
+    pub(crate) crates: Vec<Crate>,
+}
diff --git a/crates/ra_project_model/src/lib.rs b/crates/ra_project_model/src/lib.rs
index 1b18ac8361e..ded2224468b 100644
--- a/crates/ra_project_model/src/lib.rs
+++ b/crates/ra_project_model/src/lib.rs
@@ -1,15 +1,23 @@
 mod cargo_workspace;
+mod json_project;
 mod sysroot;
 
-use std::path::{Path, PathBuf};
+use std::{
+    fs::File,
+    io::BufReader,
+    path::{Path, PathBuf},
+};
 
 use failure::bail;
 use rustc_hash::FxHashMap;
 
 use ra_db::{CrateGraph, FileId, Edition};
 
+use serde_json::from_reader;
+
 pub use crate::{
     cargo_workspace::{CargoWorkspace, Package, Target, TargetKind},
+    json_project::JsonProject,
     sysroot::Sysroot,
 };
 
@@ -17,105 +25,197 @@
 pub type Result<T> = ::std::result::Result<T, ::failure::Error>;
 
 #[derive(Debug, Clone)]
-pub struct ProjectWorkspace {
-    pub cargo: CargoWorkspace,
-    pub sysroot: Sysroot,
+pub enum ProjectWorkspace {
+    /// Project workspace was discovered by running `cargo metadata` and `rustc --print sysroot`.
+    Cargo { cargo: CargoWorkspace, sysroot: Sysroot },
+    /// Project workspace was manually specified using a `rust-project.json` file.
+    Json { project: JsonProject },
 }
 
 impl ProjectWorkspace {
     pub fn discover(path: &Path) -> Result<ProjectWorkspace> {
-        let cargo_toml = find_cargo_toml(path)?;
-        let cargo = CargoWorkspace::from_cargo_metadata(&cargo_toml)?;
-        let sysroot = Sysroot::discover(&cargo_toml)?;
-        let res = ProjectWorkspace { cargo, sysroot };
-        Ok(res)
+        match find_rust_project_json(path) {
+            Some(json_path) => {
+                let file = File::open(json_path)?;
+                let reader = BufReader::new(file);
+                Ok(ProjectWorkspace::Json { project: from_reader(reader)? })
+            }
+            None => {
+                let cargo_toml = find_cargo_toml(path)?;
+                Ok(ProjectWorkspace::Cargo {
+                    cargo: CargoWorkspace::from_cargo_metadata(&cargo_toml)?,
+                    sysroot: Sysroot::discover(&cargo_toml)?,
+                })
+            }
+        }
+    }
+
+    pub fn add_roots(&self, roots: &mut Vec<PathBuf>) {
+        match self {
+            ProjectWorkspace::Json { project } => {
+                for root in &project.roots {
+                    roots.push(root.path.clone());
+                }
+            }
+            ProjectWorkspace::Cargo { cargo, sysroot } => {
+                for pkg in cargo.packages() {
+                    roots.push(pkg.root(&cargo).to_path_buf());
+                }
+                for krate in sysroot.crates() {
+                    roots.push(krate.root_dir(&sysroot).to_path_buf())
+                }
+            }
+        }
+    }
+
+    pub fn count(&self) -> usize {
+        match self {
+            ProjectWorkspace::Json { project } => project.crates.len(),
+            ProjectWorkspace::Cargo { cargo, .. } => cargo.packages().count(),
+        }
     }
 
     pub fn to_crate_graph(&self, load: &mut dyn FnMut(&Path) -> Option<FileId>) -> CrateGraph {
         let mut crate_graph = CrateGraph::default();
-        let mut sysroot_crates = FxHashMap::default();
-        for krate in self.sysroot.crates() {
-            if let Some(file_id) = load(krate.root(&self.sysroot)) {
-                sysroot_crates
-                    .insert(krate, crate_graph.add_crate_root(file_id, Edition::Edition2015));
-            }
-        }
-        for from in self.sysroot.crates() {
-            for to in from.deps(&self.sysroot) {
-                let name = to.name(&self.sysroot);
-                if let (Some(&from), Some(&to)) =
-                    (sysroot_crates.get(&from), sysroot_crates.get(&to))
-                {
-                    if let Err(_) = crate_graph.add_dep(from, name.into(), to) {
-                        log::error!("cyclic dependency between sysroot crates")
+        match self {
+            ProjectWorkspace::Json { project } => {
+                let mut crates = FxHashMap::default();
+                for (id, krate) in project.crates.iter().enumerate() {
+                    let crate_id = json_project::CrateId(id);
+                    if let Some(file_id) = load(&krate.root_module) {
+                        let edition = match krate.edition {
+                            json_project::Edition::Edition2015 => Edition::Edition2015,
+                            json_project::Edition::Edition2018 => Edition::Edition2018,
+                        };
+                        crates.insert(crate_id, crate_graph.add_crate_root(file_id, edition));
                     }
                 }
-            }
-        }
 
-        let libstd = self.sysroot.std().and_then(|it| sysroot_crates.get(&it).map(|&it| it));
-
-        let mut pkg_to_lib_crate = FxHashMap::default();
-        let mut pkg_crates = FxHashMap::default();
-        // Next, create crates for each package, target pair
-        for pkg in self.cargo.packages() {
-            let mut lib_tgt = None;
-            for tgt in pkg.targets(&self.cargo) {
-                let root = tgt.root(&self.cargo);
-                if let Some(file_id) = load(root) {
-                    let edition = pkg.edition(&self.cargo);
-                    let crate_id = crate_graph.add_crate_root(file_id, edition);
-                    if tgt.kind(&self.cargo) == TargetKind::Lib {
-                        lib_tgt = Some(crate_id);
-                        pkg_to_lib_crate.insert(pkg, crate_id);
-                    }
-                    pkg_crates.entry(pkg).or_insert_with(Vec::new).push(crate_id);
-                }
-            }
-
-            // Set deps to the std and to the lib target of the current package
-            for &from in pkg_crates.get(&pkg).into_iter().flatten() {
-                if let Some(to) = lib_tgt {
-                    if to != from {
-                        if let Err(_) = crate_graph.add_dep(from, pkg.name(&self.cargo).into(), to)
+                for (id, krate) in project.crates.iter().enumerate() {
+                    for dep in &krate.deps {
+                        let from_crate_id = json_project::CrateId(id);
+                        let to_crate_id = dep.krate;
+                        if let (Some(&from), Some(&to)) =
+                            (crates.get(&from_crate_id), crates.get(&to_crate_id))
                         {
-                            log::error!(
-                                "cyclic dependency between targets of {}",
-                                pkg.name(&self.cargo)
-                            )
+                            if let Err(_) = crate_graph.add_dep(from, dep.name.clone().into(), to) {
+                                log::error!(
+                                    "cyclic dependency {:?} -> {:?}",
+                                    from_crate_id,
+                                    to_crate_id
+                                );
+                            }
                         }
                     }
                 }
-                if let Some(std) = libstd {
-                    if let Err(_) = crate_graph.add_dep(from, "std".into(), std) {
-                        log::error!("cyclic dependency on std for {}", pkg.name(&self.cargo))
+            }
+            ProjectWorkspace::Cargo { cargo, sysroot } => {
+                let mut sysroot_crates = FxHashMap::default();
+                for krate in sysroot.crates() {
+                    if let Some(file_id) = load(krate.root(&sysroot)) {
+                        sysroot_crates.insert(
+                            krate,
+                            crate_graph.add_crate_root(file_id, Edition::Edition2015),
+                        );
+                    }
+                }
+                for from in sysroot.crates() {
+                    for to in from.deps(&sysroot) {
+                        let name = to.name(&sysroot);
+                        if let (Some(&from), Some(&to)) =
+                            (sysroot_crates.get(&from), sysroot_crates.get(&to))
+                        {
+                            if let Err(_) = crate_graph.add_dep(from, name.into(), to) {
+                                log::error!("cyclic dependency between sysroot crates")
+                            }
+                        }
                     }
                 }
-            }
-        }
 
-        // Now add a dep ednge from all targets of upstream to the lib
-        // target of downstream.
-        for pkg in self.cargo.packages() {
-            for dep in pkg.dependencies(&self.cargo) {
-                if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
+                let libstd = sysroot.std().and_then(|it| sysroot_crates.get(&it).map(|&it| it));
+
+                let mut pkg_to_lib_crate = FxHashMap::default();
+                let mut pkg_crates = FxHashMap::default();
+                // Next, create crates for each package, target pair
+                for pkg in cargo.packages() {
+                    let mut lib_tgt = None;
+                    for tgt in pkg.targets(&cargo) {
+                        let root = tgt.root(&cargo);
+                        if let Some(file_id) = load(root) {
+                            let edition = pkg.edition(&cargo);
+                            let crate_id = crate_graph.add_crate_root(file_id, edition);
+                            if tgt.kind(&cargo) == TargetKind::Lib {
+                                lib_tgt = Some(crate_id);
+                                pkg_to_lib_crate.insert(pkg, crate_id);
+                            }
+                            pkg_crates.entry(pkg).or_insert_with(Vec::new).push(crate_id);
+                        }
+                    }
+
+                    // Set deps to the std and to the lib target of the current package
                     for &from in pkg_crates.get(&pkg).into_iter().flatten() {
-                        if let Err(_) = crate_graph.add_dep(from, dep.name.clone().into(), to) {
-                            log::error!(
-                                "cyclic dependency {} -> {}",
-                                pkg.name(&self.cargo),
-                                dep.pkg.name(&self.cargo)
-                            )
+                        if let Some(to) = lib_tgt {
+                            if to != from {
+                                if let Err(_) =
+                                    crate_graph.add_dep(from, pkg.name(&cargo).into(), to)
+                                {
+                                    log::error!(
+                                        "cyclic dependency between targets of {}",
+                                        pkg.name(&cargo)
+                                    )
+                                }
+                            }
+                        }
+                        if let Some(std) = libstd {
+                            if let Err(_) = crate_graph.add_dep(from, "std".into(), std) {
+                                log::error!("cyclic dependency on std for {}", pkg.name(&cargo))
+                            }
+                        }
+                    }
+                }
+
+                // Now add a dep ednge from all targets of upstream to the lib
+                // target of downstream.
+                for pkg in cargo.packages() {
+                    for dep in pkg.dependencies(&cargo) {
+                        if let Some(&to) = pkg_to_lib_crate.get(&dep.pkg) {
+                            for &from in pkg_crates.get(&pkg).into_iter().flatten() {
+                                if let Err(_) =
+                                    crate_graph.add_dep(from, dep.name.clone().into(), to)
+                                {
+                                    log::error!(
+                                        "cyclic dependency {} -> {}",
+                                        pkg.name(&cargo),
+                                        dep.pkg.name(&cargo)
+                                    )
+                                }
+                            }
                         }
                     }
                 }
             }
         }
-
         crate_graph
     }
 }
 
+fn find_rust_project_json(path: &Path) -> Option<PathBuf> {
+    if path.ends_with("rust-project.json") {
+        return Some(path.to_path_buf());
+    }
+
+    let mut curr = Some(path);
+    while let Some(path) = curr {
+        let candidate = path.join("rust-project.json");
+        if candidate.exists() {
+            return Some(candidate);
+        }
+        curr = path.parent();
+    }
+
+    None
+}
+
 fn find_cargo_toml(path: &Path) -> Result<PathBuf> {
     if path.ends_with("Cargo.toml") {
         return Ok(path.to_path_buf());