Fix file size display to use binary units instead of decimal (#10095)

* Fix file size display to use binary units instead of decimal

- Update bytesToHumanReadable function to use 1024-based units (KB, MB, GB)
- This matches user expectations from operating systems like Windows
- Fixes issue where 87.2MB file was displayed as 91.53MB
- Update unit tests to reflect binary unit calculations
- Resolves GitHub issue #10085

Co-authored-by: Tom Moor <tom@getoutline.com>

* Make file size display platform-aware

- Use decimal units (base 1000) on macOS to match Finder behavior
- Use binary units (base 1024) on Windows to match Explorer behavior
- Import isMac utility from shared/utils/browser
- Update comprehensive tests for both platforms
- Resolves platform-specific file size display discrepancies

Co-authored-by: Tom Moor <tom@getoutline.com>

---------

Co-authored-by: codegen-sh[bot] <131295404+codegen-sh[bot]@users.noreply.github.com>
Co-authored-by: Tom Moor <tom@getoutline.com>

shared/utils/files.test.ts

@@ -1,18 +1,72 @@
 import { bytesToHumanReadable, getFileNameFromUrl } from "./files";
+import * as browser from "./browser";
+
+// Mock the browser detection
+jest.mock("./browser", () => ({
+  isMac: jest.fn(),
+}));
+
+const mockIsMac = browser.isMac as jest.MockedFunction<typeof browser.isMac>;
 
 describe("bytesToHumanReadable", () => {
-  it("outputs readable string", () => {
-    expect(bytesToHumanReadable(0)).toBe("0 Bytes");
-    expect(bytesToHumanReadable(0.0)).toBe("0 Bytes");
-    expect(bytesToHumanReadable(33)).toBe("33 Bytes");
-    expect(bytesToHumanReadable(500)).toBe("500 Bytes");
-    expect(bytesToHumanReadable(1000)).toBe("1 kB");
-    expect(bytesToHumanReadable(15000)).toBe("15 kB");
-    expect(bytesToHumanReadable(12345)).toBe("12.34 kB");
-    expect(bytesToHumanReadable(123456)).toBe("123.45 kB");
-    expect(bytesToHumanReadable(1234567)).toBe("1.23 MB");
-    expect(bytesToHumanReadable(1234567890)).toBe("1.23 GB");
-    expect(bytesToHumanReadable(undefined)).toBe("0 Bytes");
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  describe("on macOS (decimal units)", () => {
+    beforeEach(() => {
+      mockIsMac.mockReturnValue(true);
+    });
+
+    it("outputs readable string using decimal units", () => {
+      expect(bytesToHumanReadable(0)).toBe("0 Bytes");
+      expect(bytesToHumanReadable(0.0)).toBe("0 Bytes");
+      expect(bytesToHumanReadable(33)).toBe("33 Bytes");
+      expect(bytesToHumanReadable(500)).toBe("500 Bytes");
+      expect(bytesToHumanReadable(1000)).toBe("1 KB");
+      expect(bytesToHumanReadable(15000)).toBe("15 KB");
+      expect(bytesToHumanReadable(12345)).toBe("12.35 KB");
+      expect(bytesToHumanReadable(123456)).toBe("123.46 KB");
+      expect(bytesToHumanReadable(1234567)).toBe("1.23 MB");
+      expect(bytesToHumanReadable(1234567890)).toBe("1.23 GB");
+      expect(bytesToHumanReadable(undefined)).toBe("0 Bytes");
+    });
+  });
+
+  describe("on Windows/other platforms (binary units)", () => {
+    beforeEach(() => {
+      mockIsMac.mockReturnValue(false);
+    });
+
+    it("outputs readable string using binary units", () => {
+      expect(bytesToHumanReadable(0)).toBe("0 Bytes");
+      expect(bytesToHumanReadable(0.0)).toBe("0 Bytes");
+      expect(bytesToHumanReadable(33)).toBe("33 Bytes");
+      expect(bytesToHumanReadable(500)).toBe("500 Bytes");
+      expect(bytesToHumanReadable(1000)).toBe("1000 Bytes");
+      expect(bytesToHumanReadable(1024)).toBe("1 KB");
+      expect(bytesToHumanReadable(1536)).toBe("1.5 KB");
+      expect(bytesToHumanReadable(15360)).toBe("15 KB");
+      expect(bytesToHumanReadable(12345)).toBe("12.06 KB");
+      expect(bytesToHumanReadable(126464)).toBe("123.5 KB");
+      expect(bytesToHumanReadable(1048576)).toBe("1 MB");
+      expect(bytesToHumanReadable(1073741824)).toBe("1 GB");
+      expect(bytesToHumanReadable(undefined)).toBe("0 Bytes");
+    });
+  });
+
+  describe("platform-specific behavior for issue #10085", () => {
+    const fileSize = 91435827; // 87.2MB in binary, ~91.44MB in decimal
+
+    it("displays correctly on macOS (decimal)", () => {
+      mockIsMac.mockReturnValue(true);
+      expect(bytesToHumanReadable(fileSize)).toBe("91.44 MB");
+    });
+
+    it("displays correctly on Windows (binary)", () => {
+      mockIsMac.mockReturnValue(false);
+      expect(bytesToHumanReadable(fileSize)).toBe("87.2 MB");
+    });
   });
 });
 

shared/utils/files.ts

@@ -1,5 +1,8 @@
+import { isMac } from "./browser";
+
 /**
  * Converts bytes to human readable string for display
+ * Uses binary units (1024-based) on Windows and decimal units (1000-based) on macOS
  *
  * @param bytes filesize in bytes
  * @returns Human readable filesize as a string
@@ -9,19 +12,23 @@ export function bytesToHumanReadable(bytes: number | undefined) {
     return "0 Bytes";
   }
 
-  const out = ("0".repeat((bytes.toString().length * 2) % 3) + bytes).match(
-    /.{3}/g
-  );
+  // Use decimal units (base 1000) on macOS, binary units (base 1024) on other platforms
+  const useMacUnits = isMac();
+  const base = useMacUnits ? 1000 : 1024;
+  const threshold = useMacUnits ? 1000 : 1024;
 
-  if (!out || bytes < 1000) {
+  if (bytes < threshold) {
     return bytes + " Bytes";
   }
 
-  const f = (out[1] ?? "").substring(0, 2);
+  const units = ["Bytes", "KB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"];
+  const exponent = Math.floor(Math.log(bytes) / Math.log(base));
+  const value = bytes / Math.pow(base, exponent);
 
-  return `${Number(out[0])}${f === "00" ? "" : `.${f}`} ${
-    "  kMGTPEZY"[out.length]
-  }B`;
+  // Format to 2 decimal places and remove trailing zeros
+  const formatted = parseFloat(value.toFixed(2));
+
+  return `${formatted} ${units[exponent]}`;
 }
 
 /**