Add a workaround for capturing screenshots when a DOM's body element … (

#30)

* Add a workaround for capturing screenshots when a DOM's body element has no calculated height.

* Increase package version to 5.0.2

pyproject.toml

@@ -3,7 +3,7 @@ name = "uw-webdriver-recorder"
 # This version string is typically managed by the CI workflow,
 # and is changed anytime `poetry version [new version]` is run.
 # Do not revert this manually.
-version = "5.0.1"
+version = "5.0.2"
 description = "A pytest plugin for recording screenshots of selenium interactions, with other convenient features too."
 authors = ["Tom Thorogood <[email protected]>"]
 license = "Apache Software License 3.0"

tests/test_browser.py

@@ -122,6 +122,40 @@ def test_snap(browser, load_page):
     assert len(browser.pngs) == 1
 
 
+def test_snap_0_height(browser, load_page):
+    """
+    This particular case is hard to set up, but in rare
+    circumstances a page's DOM will ahve a 0-height
+    'body', which causes an error when creating our
+    normal screenshot. Here we are simply testing that, in that case,
+    the "legacy" method of creating a screenshot is used instead.
+    """
+    # Create a fake `body` object
+    orig_find_element = browser.find_element
+    orig_screenshot = browser.get_screenshot_as_base64
+    mock_body = mock.MagicMock()
+    mock_body.rect = {"height": 0}
+
+    def mock_find_element(by_: By, value: str):
+        if value == "body":
+            return mock_body
+        return orig_find_element(by_, value)
+
+    def mock_take_screenshot():
+        return orig_screenshot()
+
+    screenshot_mocker = mock.patch.object(browser, "get_screenshot_as_base64", side_effect=mock_take_screenshot)
+    find_element_mocker = mock.patch.object(browser, "find_element", mock_find_element)
+    screenshot_mock = screenshot_mocker.start()
+    find_element_mocker.start()
+    try:
+        browser.snap()
+        screenshot_mock.assert_called_once()
+    finally:
+        screenshot_mocker.stop()
+        find_element_mocker.stop()
+
+
 def test_send(browser, load_page):
     time.sleep(0.5)
     browser.send("foo", "bar")

webdriver_recorder/browser.py

@@ -237,7 +237,18 @@ def snap(self, caption: Optional[str] = None, is_error: bool = False):
         Resize the window ahead of time so the full page shows in the shot.
         """
         with self._resize_for_screenshot():
-            b64_image = self.find_element(By_.TAG_NAME, "body").screenshot_as_base64
+            # The 'body' tag is the preferred way of capturing a screenshot
+            # because it will be more consistent than having to worry about
+            # scrollbars, etc. However, in some cases, a body DOM
+            # may have content but no calculated height, which causes an
+            # error when trying to capture the screenshot.
+            # This if/else prevents the error by capturing a screenshot
+            # using the window if the body's height is false-y.
+            body = self.find_element(By_.TAG_NAME, "body")
+            if body.rect.get("height"):
+                b64_image = body.screenshot_as_base64
+            else:
+                b64_image = self.get_screenshot_as_base64()
         # The sha256 digest is used to fingerprint the image.
         # This can SIGNIFICANTLY reduce the payload of a report
         # artifact bundle by de-duplicating images, especially