Add support for Drag&Drop files into browser.

Fixes #47

Author: rasjani

atest/draganddropfile.robot

@@ -0,0 +1,27 @@
+*** Settings ***
+Documentation   Verifies that files can be dragged into browser
+Test Teardown   Close All Browsers
+Test Template   Dropzone Test
+Library         SeleniumLibrary  plugins=${CURDIR}/../src/SeleniumTestability;False;29 seconds;False
+Resource        resources.robot
+
+*** Variables ***
+${URL}    https://www.dropzonejs.com
+${FILENAME}   resources.robot
+
+
+*** Test Cases ***
+Drag And Drop File in Firefox
+  ${FF}   ${URL}
+
+Drag And Drop File in Chrome
+  ${GC}   ${URL}
+
+*** Keywords ***
+Dropzone Test
+  [Arguments]   ${BROWSER}  ${URL}
+  [Documentation]  Drags and drops image from element to another
+  Setup Web Environment   ${BROWSER}    ${URL}
+  Element Should Not Contain    xpath://div[@class="dz-filename"]    ${FILENAME}
+  Drag And Drop   file:${CURDIR}${/}${FILENAME}    id:demo-upload
+  Element Should Contain    xpath://div[@class="dz-filename"]   ${FILENAME}

src/SeleniumTestability/javascript.py

@@ -67,4 +67,32 @@
     "testability_config": """
         window.testability_config = arguments[0]
     """,
+    "drag_and_drop_file": """
+        var target = arguments[0],
+            parentElement = target.parentElement
+            offsetX = arguments[1],
+            offsetY = arguments[2],
+            document = target.ownerDocument || document,
+            window = document.defaultView || window;
+
+        var input = document.createElement('INPUT');
+        input.type = 'file';
+        input.onchange = function () {
+            var rect = target.getBoundingClientRect(),
+                x = rect.left + (offsetX || (rect.width >> 1)),
+                y = rect.top + (offsetY || (rect.height >> 1)),
+                dataTransfer = { files: this.files };
+
+            ['dragenter', 'dragover', 'drop'].forEach(function (name) {
+                var evt = document.createEvent('MouseEvent');
+                evt.initMouseEvent(name, !0, !0, window, 0, 0, 0, x, y, !1, !1, !1, !1, 0, null);
+                evt.dataTransfer = dataTransfer;
+                target.dispatchEvent(evt);
+            });
+
+            setTimeout(function () { parentElement.removeChild(input); }, 25);
+        };
+        parentElement.appendChild(input);
+        return input;
+    """,
 }

src/SeleniumTestability/plugin.py

@@ -29,6 +29,7 @@
 import re
 import json
 from time import time
+from pathlib import Path
 
 
 @wrapt.decorator
@@ -509,20 +510,39 @@ def drag_and_drop(self: "SeleniumTestability", locator: LocatorType, target: Loc
         and the ``target`` is the locator of the target. See the
         `Locating elements` section for details about the locator syntax.
 
+        If you wish to drag and drop a file from a local filesystem, you can specify the locator as `file:/full/path/to/filename`
+        and SeleniumTestability will generate a drag'n'drop events to upload a file into a given `target` element.
+
         ``html5`` parameter is optional and if provided, `drag_and_drop`will utilize
         javascript to trigger the suitable events ensuring that html5 applications
-        receive the right events
+        receive the right events. If `locator` starts with file: prefix, html5 defaults to True.
 
         Example:
-        | `Drag And Drop` | css:div#element | css:div.target |  True |
+        | `Drag And Drop` | css:div#element | css:div.target |  html5=True |
+        | `Drag And Drop` | file:/home/rasjani/testfile.txt  |  id:demo-upload |
         """
+        file_prefix = "file:"
         html5 = is_truthy(html5)
+        if file_prefix in locator:
+            html5 = True
+
         if not html5:
             self.el.drag_and_drop(locator, target)
         else:
-            from_element = self.el.find_element(locator)
             to_element = self.el.find_element(target)
-            self.ctx.driver.execute_script(JS_LOOKUP["dragdrop"], from_element, to_element)
+            filename = None
+            if type(locator) == str and file_prefix in locator:
+                filename = locator[locator.startswith(file_prefix) and len(file_prefix):]
+
+            if filename is not None:
+                if Path(filename).exists():
+                    file_input = self.driver.execute_script(JS_LOOKUP["drag_and_drop_file"], to_element, 0, 0)
+                    file_input.send_keys(filename)
+                else:
+                    raise RuntimeError(f"Unable to upload {filename} - its missing")
+            else:
+                from_element = self.el.find_element(locator)
+                self.ctx.driver.execute_script(JS_LOOKUP["dragdrop"], from_element, to_element)
 
     @log_wrapper
     @keyword