diffoscope/comparators/binwalk.py

@@ -21,7 +21,10 @@ import re
 import glob
 import logging
 
-from diffoscope.tools import python_module_missing
+from diffoscope.tools import (
+    python_module_missing,
+    get_comment_for_missing_python_module,
+)
 from diffoscope.tempfiles import get_temporary_directory
 
 from .utils.file import File
@@ -70,10 +73,11 @@ class BinwalkFile(File):
 
     @classmethod
     def recognizes(cls, file):
-        if binwalk is None:
+        if not super().recognizes(file):
             return False
 
-        if not super().recognizes(file):
+        if binwalk is None:
+            file.add_comment(get_comment_for_missing_python_module("binwalk"))
             return False
 
         # RPM files are .cpio, but let's always leave it to the RPM comparator.

diffoscope/comparators/fsimage.py

@@ -24,7 +24,7 @@ import os.path
 from diffoscope.difference import Difference
 from diffoscope.tools import python_module_missing
 from diffoscope.profiling import profile
-from diffoscope.tools import get_package_provider
+from diffoscope.tools import get_comment_for_missing_python_module
 
 from .utils.file import File
 from .utils.archive import Archive
@@ -129,9 +129,5 @@ class FsImageFile(File):
                 )
             )
         if not guestfs:
-            pkg = get_package_provider("guestfs")
-            infix = f" from the '{pkg}' package " if pkg else " "
-            self.add_comment(
-                f"Installing the 'guestfs' Python module{infix}may produce a better output."
-            )
+            self.add_comment(get_comment_for_missing_python_module("guestfs"))
         return differences

diffoscope/tools.py

@@ -191,4 +191,11 @@ def python_module_missing(name):
     python_module_missing.modules.add(name)
 
 
+def get_comment_for_missing_python_module(name):
+    pkg = get_package_provider(name)
+    infix = f" from the '{pkg}' package " if pkg else " "
+
+    return f"Installing the '{name}' Python module{infix}may produce a better output."
+
+
 python_module_missing.modules = set()