Fetchers - Define raw_content on the base fetcher, give a clear error when a fetcher can't supply the PDF

Fetchers that never set raw_content (puppeteer, playwright, selenium) crashed with
"'fetcher' object has no attribute 'raw_content'" when the response turned out to be a PDF.
Browsers render PDFs in their built-in viewer, so all they have is the viewer HTML; now the
processor reports that plainly instead of crashing or feeding HTML to pdftohtml.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changedetectionio/content_fetchers/base.py

@@ -87,6 +87,8 @@ class Fetcher():
     favicon_blob = None
     instock_data = None
     instock_data_js = ""
+    # Original response bytes (needed for PDF etc), fetchers that can't provide them leave this as None
+    raw_content = None
     screenshot_format = None
     status_code = None
     webdriver_js_execute_code = None
@@ -151,8 +153,7 @@ class Fetcher():
         Call this after content has been saved to disk.
         """
         self.content = None
-        if hasattr(self, 'raw_content'):
-            self.raw_content = None
+        self.raw_content = None
         self.screenshot = None
         self.xpath_data = None
         # Keep headers and status_code as they're small

changedetectionio/processors/text_json_diff/processor.py

@@ -43,6 +43,11 @@ class PDFToHTMLToolNotFound(ValueError):
         ValueError.__init__(self, msg)
 
 
+class PDFNotAvailableFromFetcher(ValueError):
+    def __init__(self, msg):
+        ValueError.__init__(self, msg)
+
+
 class FilterConfig:
     """Consolidates all filter and rule configurations from watch, tags, and global settings."""
 
@@ -481,6 +486,12 @@ class perform_site_check(difference_detection_processor):
 
         # PDF preprocessing
         if watch.is_pdf or stream_content_type.is_pdf:
+            # Browsers show PDFs in their built-in viewer, so a fetcher may only have the viewer's HTML
+            if not self.fetcher.raw_content or b'%PDF' not in self.fetcher.raw_content[:1024]:
+                raise PDFNotAvailableFromFetcher(
+                    "Content is a PDF but this fetcher could not provide the original PDF file, "
+                    "try the 'Basic fast Plaintext/HTTP Client' fetcher instead."
+                )
             content = content_processor.preprocess_pdf(raw_content=self.fetcher.raw_content)
             stream_content_type.is_html = True