Avoid unwanted project persistence

src/fs/fs.ts

@@ -10,20 +10,15 @@ import {
 import { fromByteArray, toByteArray } from "base64-js";
 import EventEmitter from "events";
 import sortBy from "lodash.sortby";
+import { lineNumFromUint8Array } from "../common/text-util";
 import { BoardId } from "../device/board-id";
 import { FlashDataSource, HexGenerationError } from "../device/device";
 import { Logging } from "../logging/logging";
-import { Host } from "./host";
+import { MicroPythonSource } from "../micropython/micropython";
 import { asciiToBytes, generateId } from "./fs-util";
-import {
-  FSStorage,
-  InMemoryFSStorage,
-  SessionStorageFSStorage,
-  SplitStrategyStorage,
-} from "./storage";
+import { Host } from "./host";
 import { PythonProject } from "./initial-project";
-import { lineNumFromUint8Array } from "../common/text-util";
-import { MicroPythonSource } from "../micropython/micropython";
+import { FSStorage } from "./storage";
 
 const commonFsSize = 20 * 1024;
 
@@ -168,11 +163,7 @@ export class FileSystem extends EventEmitter implements FlashDataSource {
     private microPythonSource: MicroPythonSource
   ) {
     super();
-    this.storage = new SplitStrategyStorage(
-      new InMemoryFSStorage(undefined),
-      SessionStorageFSStorage.create(),
-      logging
-    );
+    this.storage = host.createStorage(logging);
     this.project = {
       files: [],
       id: generateId(),
@@ -216,7 +207,7 @@ export class FileSystem extends EventEmitter implements FlashDataSource {
     if (!this.initializing) {
       this.initializing = (async () => {
         this._dirty = await this.storage.isDirty();
-        if (!(await this.exists(MAIN_FILE))) {
+        if (await this.host.shouldReinitializeProject(this.storage)) {
           // Do this ASAP to unblock the editor.
           this.cachedInitialProject = await this.host.createInitialProject();
           if (this.cachedInitialProject.projectName) {

src/fs/host.ts

@@ -18,6 +18,12 @@ import {
   projectFilesToBase64,
 } from "./initial-project";
 import { parseMigrationFromUrl } from "./migration";
+import {
+  FSStorage,
+  InMemoryFSStorage,
+  SessionStorageFSStorage,
+  SplitStrategyStorage,
+} from "./storage";
 
 const messages = {
   type: "pyeditor",
@@ -30,22 +36,45 @@ const messages = {
 };
 
 export interface Host {
+  createStorage(logging: Logging): FSStorage;
+  shouldReinitializeProject(storage: FSStorage): Promise<boolean>;
   createInitialProject(): Promise<PythonProject>;
   notifyReady(fs: FileSystem): void;
 }
 
 export class DefaultHost implements Host {
   constructor(private url: string = "") {}
 
-  async createInitialProject(): Promise<PythonProject> {
+  createStorage(logging: Logging): FSStorage {
+    return new SplitStrategyStorage(
+      new InMemoryFSStorage(undefined),
+      SessionStorageFSStorage.create(),
+      logging
+    );
+  }
+
+  async shouldReinitializeProject(storage: FSStorage): Promise<boolean> {
     const migration = parseMigrationFromUrl(this.url);
     if (migration) {
-      return {
+      return true;
+    }
+    return !(await storage.exists(MAIN_FILE));
+  }
+
+  async createInitialProject(): Promise<PythonProject> {
+    const migrationParseResult = parseMigrationFromUrl(this.url);
+    if (migrationParseResult) {
+      const { migration, postMigrationUrl } = migrationParseResult;
+      const project = {
         files: projectFilesToBase64({
           [MAIN_FILE]: migration.source,
         }),
         projectName: migration.meta.name,
       };
+      // Remove the migration information from the URL so that a refresh
+      // will reload from storage not remigrate.
+      window.history.replaceState(null, "", postMigrationUrl);
+      return project;
     }
     return defaultInitialProject;
   }
@@ -58,6 +87,13 @@ export class IframeHost implements Host {
     private window: Window,
     private debounceDelay: number = 1_000
   ) {}
+  createStorage(logging: Logging): FSStorage {
+    return new InMemoryFSStorage(undefined);
+  }
+  async shouldReinitializeProject(storage: FSStorage): Promise<boolean> {
+    // If there is persistence then it is the embedder's problem.
+    return true;
+  }
   createInitialProject(): Promise<PythonProject> {
     return new Promise((resolve) => {
       this.window.addEventListener("load", () =>

src/fs/migration.test.ts

@@ -7,19 +7,23 @@ import { isMigration, parseMigrationFromUrl } from "./migration";
 
 // The heart project.
 export const testMigrationUrl =
-  "http://localhost:3000/#import:#project:XQAAgACRAAAAAAAAAAA9iImmlGSt1R++5LD+ZJ36cRz46B+lhYtNRoWF0nijpaVyZlK7ACfSpeoQpgfk21st4ty06R4PEOM4sSAXBT95G3en+tghrYmE+YJp6EiYgzA9ThKkyShWq2UdvmCzqxoNfYc1wlmTqlNv/Piaz3WoSe3flvr/ItyLl0aolQlEpv4LA8A=";
+  // origin needs to match jest's testUrl
+  "http://localhost/#import:#project:XQAAgACRAAAAAAAAAAA9iImmlGSt1R++5LD+ZJ36cRz46B+lhYtNRoWF0nijpaVyZlK7ACfSpeoQpgfk21st4ty06R4PEOM4sSAXBT95G3en+tghrYmE+YJp6EiYgzA9ThKkyShWq2UdvmCzqxoNfYc1wlmTqlNv/Piaz3WoSe3flvr/ItyLl0aolQlEpv4LA8A=";
 
 describe("parseMigrationFromUrl", () => {
   it("parses valid URL", () => {
     const migration = parseMigrationFromUrl(testMigrationUrl);
     expect(migration).toEqual({
-      meta: {
-        cloudId: "microbit.org",
-        comment: "",
-        editor: "python",
-        name: "Hearts",
+      migration: {
+        meta: {
+          cloudId: "microbit.org",
+          comment: "",
+          editor: "python",
+          name: "Hearts",
+        },
+        source: `from microbit import *\r\ndisplay.show(Image.HEART)`,
       },
-      source: `from microbit import *\r\ndisplay.show(Image.HEART)`,
+      postMigrationUrl: "http://localhost/",
     });
   });
   it("undefined for nonsense", () => {

src/fs/migration.ts

@@ -23,14 +23,25 @@ export const isMigration = (v: any): v is Migration =>
   typeof v.meta?.name === "string" &&
   typeof v.source === "string";
 
-export const parseMigrationFromUrl = (url: string): Migration | undefined => {
-  const urlPart = url.split("#project:")[1];
+interface MigrationParseResult {
+  migration: Migration;
+  postMigrationUrl: string;
+}
+
+export const parseMigrationFromUrl = (
+  url: string
+): MigrationParseResult | undefined => {
+  const parts = url.split("#project:");
+  const urlPart = parts[1];
   try {
     if (urlPart) {
       const bytes = toByteArray(urlPart);
       const json = JSON.parse(LZMA.decompress(bytes));
       if (isMigration(json)) {
-        return json;
+        let postMigrationUrl = parts[0];
+        // This was previously stripped off by the versioner but for now do it ourselves:
+        postMigrationUrl = postMigrationUrl.replace(/#import:$/, "");
+        return { migration: json, postMigrationUrl };
       }
     }
   } catch (e) {