Skip auto data dir migration if target dir exists and is non-empty

chrome/content/zotero/xpcom/dataDirectory.js

@@ -428,6 +428,9 @@ Zotero.DataDirectory = {
 	},
 	
 	
+	/**
+	 * Determine if current data directory is in a legacy location
+	 */
 	canMigrate: function () {
 		// If (not default location) && (not useDataDir or within legacy location)
 		var currentDir = this.dir;
@@ -489,6 +492,12 @@ Zotero.DataDirectory = {
 			else {
 				return false;
 			}
+			
+			// Skip automatic migration if there's a non-empty directory at the new location
+			if ((yield OS.File.exists(newDir)) && !(yield Zotero.File.directoryIsEmpty(newDir))) {
+				Zotero.debug(`${newDir} exists and is non-empty -- skipping migration`);
+				return false;
+			}
 		}
 		
 		// Check for an existing pipe from other running versions of Zotero pointing at the same data

chrome/content/zotero/xpcom/file.js

@@ -486,6 +486,17 @@ Zotero.File = new function(){
 		});
 	}
 	
+	
+	/**
+	 * If directories can be moved at once, instead of recursively creating directories and moving files
+	 *
+	 * Currently this means using /bin/mv, which only works on macOS and Linux
+	 */
+	this.canMoveDirectoryAtomic = Zotero.lazy(function () {
+		var cmd = "/bin/mv";
+		return !Zotero.isWin && this.pathToFile(cmd).exists();
+	});
+	
 	/**
 	 * Move directory (using mv on macOS/Linux, recursively on Windows)
 	 *
@@ -497,7 +508,7 @@ Zotero.File = new function(){
 	this.moveDirectory = Zotero.Promise.coroutine(function* (oldDir, newDir, options = {}) {
 		var maxDepth = options.maxDepth || 10;
 		var cmd = "/bin/mv";
-		var useCmd = !Zotero.isWin && (yield OS.File.exists(cmd));
+		var useCmd = this.canMoveDirectoryAtomic();
 		
 		if (!options.allowExistingTarget && (yield OS.File.exists(newDir))) {
 			throw new Error(newDir + " exists");

test/tests/dataDirectoryTest.js

@@ -62,18 +62,17 @@ describe("Zotero.DataDirectory", function () {
 	var disableCommandMode = function () {
 		// Force non-mv mode
 		var origFunc = OS.File.exists;
-		stubs.fileExists = sinon.stub(OS.File, "exists", function (path) {
+		if (!stubs.canMoveDirectoryAtomic) {
-			if (path == '/bin/mv') {
+			stubs.canMoveDirectoryAtomic = sinon.stub(Zotero.File, "canMoveDirectoryAtomic")
-				return Zotero.Promise.resolve(false);
+				.returns(false);
-			}
+		}
-			else {
-				return origFunc(path);
-			}
-		});
 	};
 	
 	var resetCommandMode = function () {
-		stubs.fileExists.restore();
+		if (stubs.canMoveDirectoryAtomic) {
+			stubs.canMoveDirectoryAtomic.restore();
+			stubs.canMoveDirectoryAtomic = undefined;
+		}
 	};
 	
 	var populateDataDirectory = Zotero.Promise.coroutine(function* (dir, srcDir, automatic = false) {
@@ -143,7 +142,7 @@ describe("Zotero.DataDirectory", function () {
 	describe("#checkForMigration()", function () {
 		let fileMoveStub;
 		
-		before(function () {
+		beforeEach(function () {
 			disableCommandMode();
 		});
 		
@@ -156,6 +155,22 @@ describe("Zotero.DataDirectory", function () {
 			tests.push([desc, fn]);
 		}
 		
+		it("should skip automatic migration if target directory exists and is non-empty", function* () {
+			resetCommandMode();
+			
+			// No automatic migration without atomic directory move
+			if (!Zotero.File.canMoveDirectoryAtomic()) {
+				this.skip();
+			}
+			
+			yield populateDataDirectory(oldDir);
+			yield OS.File.remove(oldMigrationMarker);
+			yield OS.File.makeDir(newDir, { unixMode: 0o755 });
+			yield Zotero.File.putContentsAsync(OS.Path.join(newDir, 'a'), '');
+			
+			yield assert.eventually.isFalse(Zotero.DataDirectory.checkForMigration(oldDir, newDir));
+		});
+		
 		add("should show error on partial failure", function (automatic) {
 			return function* () {
 				yield populateDataDirectory(oldDir, null, automatic);