2 files changed, 147 insertions, 0 deletions
diff --git a/widget/tests/browser/browser.ini b/widget/tests/browser/browser.ini
new file mode 100644
index 0000000000..a50eec47e7
--- /dev/null
+++ b/widget/tests/browser/browser.ini
@@ -0,0 +1,2 @@
+[browser_test_clipboardcache.js]
+skip-if = os == 'android' || (os == 'linux' && ccov) || tsan # Bug 1613516, the test consistently timeouts on Linux coverage builds.
diff --git a/widget/tests/browser/browser_test_clipboardcache.js b/widget/tests/browser/browser_test_clipboardcache.js
new file mode 100644
index 0000000000..8364d48507
--- /dev/null
+++ b/widget/tests/browser/browser_test_clipboardcache.js
@@ -0,0 +1,145 @@
+/* -*- Mode: indent-tabs-mode: nil; js-indent-level: 2 -*- */
+/* vim: set sts=2 sw=2 et tw=80: */
+"use strict";
+
+const { AppConstants } = ChromeUtils.import(
+  "resource://gre/modules/AppConstants.jsm"
+);
+
+// Note: widget/tests/test_bug1123480.xhtml checks whether nsTransferable behaves
+// as expected with regards to private browsing mode and the clipboard cache,
+// i.e. that the clipboard is not cached to the disk when private browsing mode
+// is enabled.
+//
+// This test tests that the clipboard is not cached to the disk by IPC,
+// as a regression test for bug 1396224.
+// It indirectly uses nsTransferable, via the async navigator.clipboard API.
+
+// Create over 1 MB of sample garbage text. JavaScript strings are represented
+// by UTF16 strings, so the size is twice as much as the actual string length.
+// This value is chosen such that the size of the memory for the string exceeds
+// the kLargeDatasetSize threshold in nsTransferable.h.
+// It is also not a round number to reduce the odds of having an accidental
+// collisions with another file (since the test below looks at the file size
+// to identify the file).
+var Ipsum = "0123456789".repeat(1234321);
+var IpsumByteLength = Ipsum.length * 2;
+var SHORT_STRING_NO_CACHE = "short string that will not be cached to the disk";
+
+// Get a list of open file descriptors that refer to a file with the same size
+// as the expected data (and assume that any mutations in file descriptor counts
+// are caused by our test).
+// TODO: This logic only counts file descriptors that are still open (e.g. when
+// data persists after a copy). It does not detect cache files that exist only
+// temporarily (e.g. after a paste).
+function getClipboardCacheFDCount() {
+  let dir;
+  if (AppConstants.platform === "win") {
+    // On Windows, nsAnonymousTemporaryFile does not immediately delete a file.
+    // Instead, the Windows-specific FILE_FLAG_DELETE_ON_CLOSE flag is used,
+    // which means that the file is deleted when the last handle is closed.
+    // Apparently, this flag is unreliable (e.g. when the application crashes),
+    // so nsAnonymousTemporaryFile stores the temporary files in a subdirectory,
+    // which is cleaned up some time after start-up.
+
+    // This is just a test, and during the test we deterministically close the
+    // handles, so if FILE_FLAG_DELETE_ON_CLOSE does the thing it promises, the
+    // file is actually removed when the handle is closed.
+
+    let { FileUtils } = ChromeUtils.import(
+      "resource://gre/modules/FileUtils.jsm"
+    );
+    // Path from nsAnonymousTemporaryFile.cpp, GetTempDir.
+    dir = FileUtils.getFile("TmpD", ["mozilla-temp-files"]);
+  } else {
+    dir = Cc["@mozilla.org/file/local;1"].createInstance(Ci.nsIFile);
+    dir.initWithPath("/dev/fd");
+  }
+  let count = 0;
+  for (let fdFile of dir.directoryEntries) {
+    let fileSize;
+    try {
+      fileSize = fdFile.fileSize;
+    } catch (e) {
+      // This can happen on macOS.
+      continue;
+    }
+    if (fileSize === IpsumByteLength) {
+      // Assume that the file was created by us if the size matches.
+      ++count;
+    }
+  }
+  return count;
+}
+
+async function testCopyPaste(isPrivate) {
+  let win = await BrowserTestUtils.openNewBrowserWindow({ private: isPrivate });
+  let tab = await BrowserTestUtils.openNewForegroundTab(win);
+  let browser = tab.linkedBrowser;
+
+  // Sanitize environment
+  await ContentTask.spawn(browser, SHORT_STRING_NO_CACHE, async shortStr => {
+    await content.navigator.clipboard.writeText(shortStr);
+  });
+
+  let initialFdCount = getClipboardCacheFDCount();
+
+  await SpecialPowers.spawn(browser, [Ipsum], async largeString => {
+    await content.navigator.clipboard.writeText(largeString);
+  });
+
+  let fdCountAfterCopy = getClipboardCacheFDCount();
+  if (isPrivate) {
+    is(fdCountAfterCopy, initialFdCount, "Private write");
+  } else {
+    is(fdCountAfterCopy, initialFdCount + 1, "Cached write");
+  }
+
+  let readStr = await SpecialPowers.spawn(browser, [], async () => {
+    let { document } = content;
+    document.body.contentEditable = true;
+    document.body.focus();
+    let pastePromise = new Promise(resolve => {
+      document.addEventListener(
+        "paste",
+        e => {
+          resolve(e.clipboardData.getData("text/plain"));
+        },
+        { once: true }
+      );
+    });
+    document.execCommand("paste");
+    return pastePromise;
+  });
+  ok(readStr === Ipsum, "Read what we pasted");
+
+  if (isPrivate) {
+    is(getClipboardCacheFDCount(), fdCountAfterCopy, "Private read");
+  } else {
+    // Upon reading from the clipboard, a temporary nsTransferable is used, for
+    // which the cache is disabled. The content process does not cache clipboard
+    // data either. So the file descriptor count should be identical.
+    is(getClipboardCacheFDCount(), fdCountAfterCopy, "Read not cached");
+  }
+
+  // Cleanup.
+  await SpecialPowers.spawn(
+    browser,
+    [SHORT_STRING_NO_CACHE],
+    async shortStr => {
+      await content.navigator.clipboard.writeText(shortStr);
+    }
+  );
+  is(getClipboardCacheFDCount(), initialFdCount, "Drop clipboard cache if any");
+
+  BrowserTestUtils.removeTab(tab);
+  await BrowserTestUtils.closeWindow(win);
+}
+
+add_task(async function test_private() {
+  await testCopyPaste(true);
+});
+
+add_task(async function test_non_private() {
+  await testCopyPaste(false);
+});