Include now-missing project folders in initial state key computation

spec/atom-environment-spec.js

@@ -742,6 +742,27 @@ describe('AtomEnvironment', () => {
           expect(atom.project.getPaths()).toEqual([])
         })
 
+        it('includes missing mandatory project folders in computation of initial state key', async () => {
+          const existingDir = path.join(__dirname, 'fixtures')
+          const missingDir = path.join(__dirname, 'no')
+
+          atom.loadState.andCallFake(function (key) {
+            if (key === `${existingDir}:${missingDir}`) {
+              return Promise.resolve(state)
+            } else {
+              return Promise.resolve(null)
+            }
+          })
+
+          await atom.openLocations([
+            {pathToOpen: existingDir},
+            {pathToOpen: missingDir, mustBeDirectory: true}
+          ])
+
+          expect(atom.attemptRestoreProjectStateForPaths).toHaveBeenCalledWith(state, [existingDir], [])
+          expect(atom.project.getPaths(), [existingDir])
+        })
+
         it('opens the specified files', async () => {
           await atom.openLocations([{pathToOpen: __dirname}, {pathToOpen: __filename}])
           expect(atom.attemptRestoreProjectStateForPaths).toHaveBeenCalledWith(state, [__dirname], [__filename])

src/atom-environment.js

@@ -1404,7 +1404,7 @@ or use Pane::saveItemAs for programmatic saving.`)
           // Found: add as a project folder
           foldersToAddToProject.add(directory.getPath())
         } else if (location.mustBeDirectory) {
-          // Not found and must be a directory: add to missing list
+          // Not found and must be a directory: add to missing list and use to derive state key
           missingFolders.push(location)
         } else {
           // Not found: open as a new file
@@ -1416,8 +1416,12 @@ or use Pane::saveItemAs for programmatic saving.`)
     }
 
     let restoredState = false
-    if (foldersToAddToProject.size > 0) {
-      const state = await this.loadState(this.getStateKey(Array.from(foldersToAddToProject)))
+    if (foldersToAddToProject.size > 0 || missingFolders.length > 0) {
+      // Include missing folders in the state key so that sessions restored with no-longer-present project root folders
+      // don't lose data.
+      const foldersForStateKey = Array.from(foldersToAddToProject)
+        .concat(missingFolders.map(location => location.pathToOpen))
+      const state = await this.loadState(this.getStateKey(Array.from(foldersForStateKey)))
 
       // only restore state if this is the first path added to the project
       if (state && needsProjectPaths) {