Merge pull request #818 from plotly/testing-download

✨ add download support for both browser

dash/testing/browser.py

@@ -30,11 +30,13 @@ def __init__(
         headless=False,
         options=None,
         remote=None,
+        download_path=None,
         wait_timeout=10,
     ):
         self._browser = browser.lower()
         self._headless = headless
         self._options = options
+        self._download_path = download_path
         self._wait_timeout = wait_timeout
 
         self._driver = self.get_webdriver(remote)
@@ -55,6 +57,10 @@ def __init__(
         )
         self.percy_runner.initialize_build()
 
+        logger.debug("initialize browser with arguments")
+        logger.debug("  headless => %s", self._headless)
+        logger.debug("  download_path => %s", self._download_path)
+
     def __enter__(self):
         return self
 
@@ -273,9 +279,38 @@ def _get_chrome(self):
         if "DASH_TEST_CHROMEPATH" in os.environ:
             options.binary_location = os.environ["DASH_TEST_CHROMEPATH"]
 
+        options.add_experimental_option(
+            "prefs",
+            {
+                "download.default_directory": self.download_path,
+                "download.prompt_for_download": False,
+                "download.directory_upgrade": True,
+                "safebrowsing.enabled": False,
+                "safebrowsing.disable_download_protection": True,
+            },
+        )
+
         chrome = webdriver.Chrome(
             options=options, desired_capabilities=capabilities
         )
+
+        # https://bugs.chromium.org/p/chromium/issues/detail?id=696481
+        if self._headless:
+            # pylint: disable=protected-access
+            chrome.command_executor._commands["send_command"] = (
+                "POST",
+                "/session/$sessionId/chromium/send_command",
+            )
+            params = {
+                "cmd": "Page.setDownloadBehavior",
+                "params": {
+                    "behavior": "allow",
+                    "downloadPath": self.download_path,
+                },
+            }
+            res = chrome.execute("send_command", params)
+            logger.debug("enabled headless download returns %s", res)
+
         chrome.set_window_position(0, 0)
         return chrome
 
@@ -288,16 +323,14 @@ def _get_firefox(self):
 
         # https://developer.mozilla.org/en-US/docs/Download_Manager_preferences
         fp = webdriver.FirefoxProfile()
-
-        # this will be useful if we wanna test download csv or other data
-        # files with selenium
-        # TODO this could be replaced with a tmpfixture from pytest too
-        fp.set_preference("browser.download.dir", "/tmp")
+        fp.set_preference("browser.download.dir", self.download_path)
         fp.set_preference("browser.download.folderList", 2)
-        fp.set_preference("browser.download.manager.showWhenStarting", False)
-
+        fp.set_preference(
+            "browser.helperApps.neverAsk.saveToDisk",
+            "application/octet-stream",  # this MIME is generic for binary
+        )
         return webdriver.Firefox(
-            fp, options=options, capabilities=capabilities
+            firefox_profile=fp, options=options, capabilities=capabilities
         )
 
     @staticmethod
@@ -363,3 +396,7 @@ def server_url(self, value):
         """
         self._url = value
         self.wait_for_page()
+
+    @property
+    def download_path(self):
+        return self._download_path

dash/testing/plugin.py

@@ -80,21 +80,23 @@ def dash_process_server():
 
 
 @pytest.fixture
-def dash_br(request):
+def dash_br(request, tmpdir):
     with Browser(
         browser=request.config.getoption("webdriver"),
         headless=request.config.getoption("headless"),
         options=request.config.hook.pytest_setup_options(),
+        download_path=tmpdir.mkdir('download').strpath
     ) as browser:
         yield browser
 
 
 @pytest.fixture
-def dash_duo(request, dash_thread_server):
+def dash_duo(request, dash_thread_server, tmpdir):
     with DashComposite(
         dash_thread_server,
         browser=request.config.getoption("webdriver"),
         headless=request.config.getoption("headless"),
         options=request.config.hook.pytest_setup_options(),
+        download_path=tmpdir.mkdir('download').strpath
     ) as dc:
         yield dc