fileStorage/reducers: drop use of Set

Using set causes problems with tooling that mocks the global app state,
so stick with arrays.

src/editor/sagas.test.ts

@@ -140,7 +140,7 @@ describe('setEditSession', () => {
     it('should wait for storage to be initialized', async () => {
         const mockEditor = mock<monaco.editor.ICodeEditor>();
         const saga = new AsyncSaga(editor, {
-            fileStorage: { isInitialized: false, fileNames: new Set() },
+            fileStorage: { isInitialized: false, fileNames: [] },
         });
 
         saga.put(setEditSession(mockEditor));
@@ -155,7 +155,7 @@ describe('setEditSession', () => {
     it('should load main.py', async () => {
         const mockEditor = mock<monaco.editor.ICodeEditor>();
         const saga = new AsyncSaga(editor, {
-            fileStorage: { isInitialized: true, fileNames: new Set(['main.py']) },
+            fileStorage: { isInitialized: true, fileNames: ['main.py'] },
         });
 
         saga.put(setEditSession(mockEditor));
@@ -175,7 +175,7 @@ describe('setEditSession', () => {
     it('should not raise error if main.py does not exist', async () => {
         const mockEditor = mock<monaco.editor.ICodeEditor>();
         const saga = new AsyncSaga(editor, {
-            fileStorage: { isInitialized: true, fileNames: new Set() },
+            fileStorage: { isInitialized: true, fileNames: [] },
         });
 
         saga.put(setEditSession(mockEditor));

src/editor/sagas.ts

@@ -115,7 +115,7 @@ function* handleSetEditSession(action: ReturnType<typeof setEditSession>): Gener
 
     const fileList = yield* select((s: RootState) => s.fileStorage.fileNames);
 
-    if (!fileList.has(currentFileName)) {
+    if (!fileList.includes(currentFileName)) {
         // The file doesn't exist in storage, so don't try to open it.
         yield* put(didSetEditSession(action.editSession));
         return;

src/fileStorage/reducers.test.ts

@@ -14,7 +14,7 @@ type State = ReturnType<typeof reducers>;
 test('initial state', () => {
     expect(reducers(undefined, {} as AnyAction)).toMatchInlineSnapshot(`
         Object {
-          "fileNames": Set {},
+          "fileNames": Array [],
           "isInitialized": false,
         }
     `);
@@ -33,31 +33,31 @@ test('fileNames', () => {
     // initialization populates file list
     expect(
         reducers(
-            { fileNames: new Set() } as State,
+            { fileNames: [] as ReadonlyArray<string> } as State,
             fileStorageDidInitialize([testFileName]),
         ).fileNames,
-    ).toEqual(new Set([testFileName]));
+    ).toEqual([testFileName]);
 
     // if item is not in set, add it
     expect(
         reducers(
-            { fileNames: new Set() } as State,
+            { fileNames: [] as ReadonlyArray<string> } as State,
             fileStorageDidChangeItem(testFileName),
         ).fileNames,
-    ).toEqual(new Set([testFileName]));
+    ).toEqual([testFileName]);
 
     // if item is already in set, there should not be duplicates
     expect(
         reducers(
-            { fileNames: new Set([testFileName]) } as State,
+            { fileNames: [testFileName] as ReadonlyArray<string> } as State,
             fileStorageDidChangeItem(testFileName),
         ).fileNames,
-    ).toEqual(new Set([testFileName]));
+    ).toEqual([testFileName]);
 
     // if item is in set, it should be removed
     expect(
         reducers(
-            { fileNames: new Set([testFileName]) } as State,
+            { fileNames: [testFileName] as ReadonlyArray<string> } as State,
             fileStorageDidRemoveItem(testFileName),
         ).fileNames,
     ).not.toContain(testFileName);

src/fileStorage/reducers.ts

@@ -16,17 +16,21 @@ const isInitialized: Reducer<boolean> = (state = false, action) => {
     return state;
 };
 
-const fileNames: Reducer<Set<string>> = (state = new Set(), action) => {
+const fileNames: Reducer<ReadonlyArray<string>> = (state = [], action) => {
     if (fileStorageDidInitialize.matches(action)) {
-        return new Set(action.fileNames);
+        return [...action.fileNames];
     }
 
     if (fileStorageDidChangeItem.matches(action)) {
-        return new Set([...state, action.fileName]);
+        if (state.includes(action.fileName)) {
+            return state;
+        }
+
+        return [...state, action.fileName];
     }
 
     if (fileStorageDidRemoveItem.matches(action)) {
-        return new Set([...state].filter((value) => value !== action.fileName));
+        return [...state].filter((value) => value !== action.fileName);
     }
 
     return state;