screenshot: add an option to not retake existing screenshots

frontools/cli.py

@@ -102,6 +102,7 @@ def prune_caches(cache_names: list[str]) -> None:
 @argument("source", type=str)
 @option("-o", "--output-directory", type=PathArgument(), default=None)
 @option("-w", "--screen-width", type=int, default=None)
+@option("-c", "--continue", "continue_", type=bool, help="Don't reshot already existing screenshots", count=True)
 @_async_command
 @pass_obj
 async def screenshot_diff_cli(
@@ -109,9 +110,10 @@ async def screenshot_diff_cli(
     source: str,
     output_directory: Optional[str],
     screen_width: Optional[int],
+    continue_: bool
 ) -> None:
     """Generate screenshot diffs"""
-    await screenshot_diff(config, source, output_directory, screen_width=screen_width)
+    await screenshot_diff(config, source, output_directory, screen_width=screen_width, continue_=continue_)
 
 
 if __name__ == "__main__":

frontools/screenshot.py

@@ -19,6 +19,7 @@ async def screenshot_diff(
     config: Config,
     right_source_name: str,
     output_directory: Optional[str],
+    continue_: bool = False,
     screen_width: Optional[int] = None,
 ) -> None:
     """Compare pages with or without local css"""
@@ -28,7 +29,7 @@ async def screenshot_diff(
     else:
         output_path = Path(output_directory)
 
-    output_path.mkdir(parents=True)
+    output_path.mkdir(parents=True, exist_ok=True)
     left_source = config.source
     right_source = config.get_source(right_source_name)
 
@@ -45,6 +46,7 @@ async def screenshot_diff(
                             url,
                             output_path,
                             theme_name,
+                            continue_
                         ),
                     )
                     for (theme_name, url) in config.urls
@@ -59,7 +61,16 @@ async def _diff_url(
     url: str,
     output_path: Path,
     theme_name: str,
+    continue_: bool
 ) -> None:
+
+    url_slug = get_url_slug(url)
+    left_filename = output_path / f"{theme_name}_{url_slug}_left"
+    right_filename = output_path / f"{theme_name}_{url_slug}_right"
+
+    if left_filename.is_file() and right_filename.is_file() and continue_:
+        return
+
     left_bytes = await _screenshot_url(left, url)
     right_bytes = await _screenshot_url(right, url)
 
@@ -76,14 +87,12 @@ async def _diff_url(
     if not diff.getbbox():
         return
 
-    url_slug = get_url_slug(url)
-    if not output_path.is_dir():
-        output_path.mkdir()
+    output_path.mkdir(parents=True, exist_ok=True)
 
-    with open(output_path / f"{theme_name}_{url_slug}_left", "wb") as screenshot_file:
+    with open(left_filename, "wb") as screenshot_file:
         screenshot_file.write(left_bytes)
 
-    with open(output_path / f"{theme_name}_{url_slug}_right", "wb") as screenshot_file:
+    with open(right_filename, "wb") as screenshot_file:
         screenshot_file.write(right_bytes)