Helping prevention of accidental directory exclusion when using the -…

…-export-on-exit option (#4127)

* Adding condition to prevent the user from setting the export data folder to the CWD, inflicting in directory exclusion after stopping the emulators

* Added another test case when the user sets the --export-on-exit implicitly via the set of --import

* Improved the message presented to user
Fixed a cenario where the user could ingress a pattern of cwd and it would fail incorrectly

Co-authored-by: Yuchen Shi <yuchenshi@google.com>

src/emulator/commandUtils.ts

@@ -45,6 +45,8 @@ export const EXPORT_ON_EXIT_USAGE_ERROR =
   `"${FLAG_EXPORT_ON_EXIT_NAME}" must be used with "${FLAG_IMPORT}"` +
   ` or provide a dir directly to "${FLAG_EXPORT_ON_EXIT}"`;
 
+export const EXPORT_ON_EXIT_CWD_DANGER = `"${FLAG_EXPORT_ON_EXIT_NAME}" must not point to the current directory or parents. Please choose a new/dedicated directory for exports.`;
+
 export const FLAG_UI = "--ui";
 export const DESC_UI = "run the Emulator UI";
 
@@ -203,6 +205,10 @@ export function setExportOnExitOptions(options: any) {
       // firebase emulators:start --debug --import '' --export-on-exit ''
       throw new FirebaseError(EXPORT_ON_EXIT_USAGE_ERROR);
     }
+
+    if (path.resolve(".").startsWith(path.resolve(options.exportOnExit))) {
+      throw new FirebaseError(EXPORT_ON_EXIT_CWD_DANGER);
+    }
   }
   return;
 }

src/test/emulators/commandUtils.spec.ts

@@ -1,14 +1,73 @@
 import * as commandUtils from "../../emulator/commandUtils";
 import { expect } from "chai";
 import { FirebaseError } from "../../error";
-import { EXPORT_ON_EXIT_USAGE_ERROR } from "../../emulator/commandUtils";
+import { EXPORT_ON_EXIT_USAGE_ERROR, EXPORT_ON_EXIT_CWD_DANGER } from "../../emulator/commandUtils";
+import { delimiter, join, resolve } from "path";
+import * as sinon from "sinon";
 
 describe("commandUtils", () => {
   const testSetExportOnExitOptions = (options: any): any => {
     commandUtils.setExportOnExitOptions(options);
     return options;
   };
 
+  describe("Mocked path resolve", () => {
+    const mockCWD = "/a/resolved/path/example";
+    const mockDestinationDir = "/path/example";
+
+    let pathStub: sinon.SinonStub;
+    beforeEach(() => {
+      pathStub = sinon.stub(require("path"), "resolve").callsFake((path) => {
+        return path === "." ? mockCWD : mockDestinationDir;
+      });
+    });
+
+    afterEach(() => {
+      pathStub.reset();
+    });
+
+    it("Should not block if destination contains a match to the CWD", () => {
+      const directoryToAllow = mockDestinationDir;
+      expect(testSetExportOnExitOptions({ exportOnExit: directoryToAllow }).exportOnExit).to.equal(
+        directoryToAllow
+      );
+    });
+  });
+
+  /**
+   * Currently, setting the --export-on-exit as the current CWD can inflict on
+   * full directory deletion
+   */
+  const directoriesThatShouldFail = [
+    ".", // The current dir
+    "./", // The current dir with /
+    resolve("."), // An absolute path
+    resolve(".."), // A folder that directs to the CWD
+    resolve("../.."), // Another folder that directs to the CWD
+  ];
+
+  directoriesThatShouldFail.forEach((dir) => {
+    it(`Should disallow the user to set the current folder (ex: ${dir}) as --export-on-exit option`, () => {
+      expect(() => testSetExportOnExitOptions({ exportOnExit: dir })).to.throw(
+        EXPORT_ON_EXIT_CWD_DANGER
+      );
+      const cwdSubDir = join(dir, "some-dir");
+      expect(testSetExportOnExitOptions({ exportOnExit: cwdSubDir }).exportOnExit).to.equal(
+        cwdSubDir
+      );
+    });
+  });
+
+  it("Should disallow the user to set the current folder via the --import flag", () => {
+    expect(() => testSetExportOnExitOptions({ import: ".", exportOnExit: true })).to.throw(
+      EXPORT_ON_EXIT_CWD_DANGER
+    );
+    const cwdSubDir = join(".", "some-dir");
+    expect(
+      testSetExportOnExitOptions({ import: cwdSubDir, exportOnExit: true }).exportOnExit
+    ).to.equal(cwdSubDir);
+  });
+
   it("should validate --export-on-exit options", () => {
     expect(testSetExportOnExitOptions({ import: "./data" }).exportOnExit).to.be.undefined;
     expect(