diff-quality plugins should support "--options" and report files (#305)

diff_cover/diff_quality_tool.py

@@ -308,6 +308,7 @@ def main(argv=None, directory=None):
         if first_char == last_char and first_char in ('"', "'"):
             user_options = user_options[1:-1]
     reporter = None
+    reporter_factory_fn = None
     driver = QUALITY_DRIVERS.get(tool)
     if driver is None:
         # The requested tool is not built into diff_cover. See if another Python
@@ -321,29 +322,29 @@ def main(argv=None, directory=None):
         )
         for hookimpl in hooks.get_hookimpls():
             if hookimpl.plugin_name == tool:
-                reporter = hookimpl.function()
+                reporter_factory_fn = hookimpl.function
                 break
 
-    if reporter or driver:
+    if reporter or driver or reporter_factory_fn:
         input_reports = []
         try:
+            for path in arg_dict["input_reports"]:
+                try:
+                    input_reports.append(open(path, "rb"))
+                except OSError:
+                    LOGGER.error("Could not load report '%s'", path)
+                    return 1
             if driver is not None:
                 # If we've been given pre-generated reports,
                 # try to open the files
-
-                for path in arg_dict["input_reports"]:
-                    try:
-                        input_reports.append(open(path, "rb"))
-                    except OSError:
-                        LOGGER.error("Could not load report '%s'", path)
-                        return 1
-
                 if arg_dict["report_root_path"]:
                     driver.add_driver_args(
                         report_root_path=arg_dict["report_root_path"]
                     )
 
                 reporter = QualityReporter(driver, input_reports, user_options)
+            elif reporter_factory_fn:
+                reporter = reporter_factory_fn(reports=input_reports, options=user_options)
 
             percent_passing = generate_quality_report(
                 reporter,