Fix bolt add not reinstalling packages from the project root

src/commands/__tests__/add.test.js

@@ -79,7 +79,7 @@ describe('bolt add', () => {
           cwd: projectDir
         })
       );
-      expect(yarn.add).toHaveBeenCalledTimes(0);
+      expect(yarn.add).toHaveBeenCalledTimes(1);
     });
 
     test('adding new dependency with --dev flag', async () => {

src/utils/__tests__/addDependenciesToPackages.test.js

@@ -72,13 +72,30 @@ describe('utils/addDependenciesToPackages', () => {
     );
   });
 
-  test('it should not yarn install packages that are already installed', async () => {
+  test('it should not yarn install packages that are already installed when run from a workspace', async () => {
+    let rootDir = f.copy('nested-workspaces');
+    let project = await Project.init(rootDir);
+    let packages = await project.getPackages();
+    let pkg = project.getPackageByName(packages, 'foo');
+    if (!pkg) throw new Error('missing foo');
+
+    await addDependenciesToPackage(project, pkg, [{ name: 'react' }]);
+
+    expect(unsafeYarn.add).toHaveBeenCalledTimes(0);
+  });
+
+  test('it should yarn install packages that are already installed when run from the project root', async () => {
     let cwd = f.copy('nested-workspaces');
     let project = await Project.init(cwd);
 
     await addDependenciesToPackage(project, project.pkg, [{ name: 'react' }]);
 
-    expect(unsafeYarn.add).toHaveBeenCalledTimes(0);
+    expect(unsafeYarn.add).toHaveBeenCalledTimes(1);
+    expect(unsafeYarn.add).toHaveBeenCalledWith(
+      project.pkg,
+      [{ name: 'react' }],
+      'dependencies'
+    );
   });
 
   test('it should throw if version does not match version in project config', async () => {

src/utils/addDependenciesToPackages.js

@@ -21,20 +21,23 @@ export default async function addDependenciesToPackage(
   let projectDependencies = project.pkg.getAllDependencies();
   let pkgDependencies = pkg.getAllDependencies();
   let { graph: depGraph } = await project.getDependencyGraph(packages);
+  let inProjectRoot = pkg.isSamePackage(project.pkg);
 
   let dependencyNames = dependencies.map(dep => dep.name);
   let externalDeps = dependencies.filter(dep => !depGraph.has(dep.name));
   let internalDeps = dependencies.filter(dep => depGraph.has(dep.name));
 
   let externalDepsToInstallForProject = externalDeps.filter(
-    dep => !projectDependencies.has(dep.name)
+    // If we are in the project, always (re)install external deps to keep same behaviour as yarn
+    // Otherwise, if in a workspace, only project install if it isn't already installed
+    dep => inProjectRoot || !projectDependencies.has(dep.name)
   );
   if (externalDepsToInstallForProject.length !== 0) {
     await yarn.add(project.pkg, externalDepsToInstallForProject, type);
     // we reinitialise the project config because it will be modified externally by yarn
     project = await Project.init(project.pkg.dir);
   }
-  if (pkg.isSamePackage(project.pkg)) {
+  if (inProjectRoot) {
     if (internalDeps.length > 0) {
       throw new BoltError(
         messages.cannotInstallWorkspaceInProject(internalDeps[0].name)