diff --git a/rust/project_json.go b/rust/project_json.go
new file mode 100644
index 0000000..909aebc
--- /dev/null
+++ b/rust/project_json.go
@@ -0,0 +1,161 @@
+// Copyright 2020 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rust
+
+import (
+	"encoding/json"
+	"fmt"
+	"path"
+
+	"android/soong/android"
+)
+
+// This singleton collects Rust crate definitions and generates a JSON file
+// (${OUT_DIR}/soong/rust-project.json) which can be use by external tools,
+// such as rust-analyzer. It does so when either make, mm, mma, mmm or mmma is
+// called.  This singleton is enabled only if SOONG_GEN_RUST_PROJECT is set.
+// For example,
+//
+//   $ SOONG_GEN_RUST_PROJECT=1 m nothing
+
+func init() {
+	android.RegisterSingletonType("rust_project_generator", rustProjectGeneratorSingleton)
+}
+
+func rustProjectGeneratorSingleton() android.Singleton {
+	return &projectGeneratorSingleton{}
+}
+
+type projectGeneratorSingleton struct{}
+
+const (
+	// Environment variables used to control the behavior of this singleton.
+	envVariableCollectRustDeps = "SOONG_GEN_RUST_PROJECT"
+	rustProjectJsonFileName    = "rust-project.json"
+)
+
+// The format of rust-project.json is not yet finalized. A current description is available at:
+// https://github.com/rust-analyzer/rust-analyzer/blob/master/docs/user/manual.adoc#non-cargo-based-projects
+type rustProjectDep struct {
+	Crate int    `json:"crate"`
+	Name  string `json:"name"`
+}
+
+type rustProjectCrate struct {
+	RootModule string           `json:"root_module"`
+	Edition    string           `json:"edition,omitempty"`
+	Deps       []rustProjectDep `json:"deps"`
+	Cfgs       []string         `json:"cfgs"`
+}
+
+type rustProjectJson struct {
+	Roots  []string           `json:"roots"`
+	Crates []rustProjectCrate `json:"crates"`
+}
+
+// crateInfo is used during the processing to keep track of the known crates.
+type crateInfo struct {
+	ID   int
+	Deps map[string]int
+}
+
+func mergeDependencies(ctx android.SingletonContext, project *rustProjectJson,
+	knownCrates map[string]crateInfo, module android.Module,
+	crate *rustProjectCrate, deps map[string]int) {
+
+	//TODO(tweek): The stdlib dependencies do not appear here. We need to manually add them.
+	ctx.VisitDirectDeps(module, func(child android.Module) {
+		childId, childName, ok := appendLibraryAndDeps(ctx, project, knownCrates, child)
+		if !ok {
+			return
+		}
+		if _, ok = deps[childName]; ok {
+			return
+		}
+		crate.Deps = append(crate.Deps, rustProjectDep{Crate: childId, Name: childName})
+		deps[childName] = childId
+	})
+}
+
+// appendLibraryAndDeps creates a rustProjectCrate for the module argument and
+// appends it to the rustProjectJson struct.  It visits the dependencies of the
+// module depth-first. If the current module is already in knownCrates, its
+// its dependencies are merged. Returns a tuple (id, crate_name, ok).
+func appendLibraryAndDeps(ctx android.SingletonContext, project *rustProjectJson,
+	knownCrates map[string]crateInfo, module android.Module) (int, string, bool) {
+	rModule, ok := module.(*Module)
+	if !ok {
+		return 0, "", false
+	}
+	if rModule.compiler == nil {
+		return 0, "", false
+	}
+	rustLib, ok := rModule.compiler.(*libraryDecorator)
+	if !ok {
+		return 0, "", false
+	}
+	crateName := rModule.CrateName()
+	if cInfo, ok := knownCrates[crateName]; ok {
+		// We have seen this crate already; merge any new dependencies.
+		crate := project.Crates[cInfo.ID]
+		mergeDependencies(ctx, project, knownCrates, module, &crate, cInfo.Deps)
+		return cInfo.ID, crateName, true
+	}
+	crate := rustProjectCrate{Deps: make([]rustProjectDep, 0), Cfgs: make([]string, 0)}
+	src := rustLib.Properties.Srcs[0]
+	crate.RootModule = path.Join(ctx.ModuleDir(rModule), src)
+	crate.Edition = getEdition(rustLib.baseCompiler)
+
+	deps := make(map[string]int)
+	mergeDependencies(ctx, project, knownCrates, module, &crate, deps)
+
+	id := len(project.Crates)
+	knownCrates[crateName] = crateInfo{ID: id, Deps: deps}
+	project.Crates = append(project.Crates, crate)
+	// rust-analyzer requires that all crates belong to at least one root:
+	// https://github.com/rust-analyzer/rust-analyzer/issues/4735.
+	project.Roots = append(project.Roots, path.Dir(crate.RootModule))
+	return id, crateName, true
+}
+
+func (r *projectGeneratorSingleton) GenerateBuildActions(ctx android.SingletonContext) {
+	if !ctx.Config().IsEnvTrue(envVariableCollectRustDeps) {
+		return
+	}
+
+	project := rustProjectJson{}
+	knownCrates := make(map[string]crateInfo)
+	ctx.VisitAllModules(func(module android.Module) {
+		appendLibraryAndDeps(ctx, &project, knownCrates, module)
+	})
+
+	path := android.PathForOutput(ctx, rustProjectJsonFileName)
+	err := createJsonFile(project, path)
+	if err != nil {
+		ctx.Errorf(err.Error())
+	}
+}
+
+func createJsonFile(project rustProjectJson, rustProjectPath android.WritablePath) error {
+	buf, err := json.MarshalIndent(project, "", "  ")
+	if err != nil {
+		return fmt.Errorf("JSON marshal of rustProjectJson failed: %s", err)
+	}
+	err = android.WriteFileToOutputDir(rustProjectPath, buf, 0666)
+	if err != nil {
+		return fmt.Errorf("Writing rust-project to %s failed: %s", rustProjectPath.String(), err)
+	}
+	return nil
+}