Remove filtering of 0 size files in engine

Files size is already able to be filtered at a higher level, some users
may decide to see zero length files. Fix #321.

core/engine.py

@@ -288,8 +288,7 @@ def getmatches_by_contents(files, bigsize=0, j=job.nulljob):
     """
     size2files = defaultdict(set)
     for f in files:
-        if f.size:
-            size2files[f.size].add(f)
+        size2files[f.size].add(f)
     del files
     possible_matches = [files for files in size2files.values() if len(files) > 1]
     del size2files
@@ -300,6 +299,10 @@ def getmatches_by_contents(files, bigsize=0, j=job.nulljob):
         for first, second in itertools.combinations(group, 2):
             if first.is_ref and second.is_ref:
                 continue  # Don't spend time comparing two ref pics together.
+            if first.size == 0 and second.size == 0:
+                # skip md5 for zero length files
+                result.append(Match(first, second, 100))
+                continue
             if first.md5partial == second.md5partial:
                 if bigsize > 0 and first.size > bigsize:
                     if first.md5samples == second.md5samples:

core/tests/engine_test.py

@@ -530,10 +530,6 @@ class TestCaseGetMatches:
 
 
 class TestCaseGetMatchesByContents:
-    def test_dont_compare_empty_files(self):
-        o1, o2 = no(size=0), no(size=0)
-        assert not getmatches_by_contents([o1, o2])
-
     def test_big_file_partial_hashes(self):
         smallsize = 1
         bigsize = 100 * 1024 * 1024  # 100MB