filter: try to detect 0-byte DOC files based on extension

Commit ae1f51b4888a3aa14837ac6e4083f33b2176ca45 (tdf#123476 filter: try
to detect 0-byte files based on extension, 2020-10-28), already
implemented this UNO-based import filters, do the same for built-in
filters as well.

Another problem in filter/ was to pick the WW6 filter for .doc --
require export+preferred support in the filter to get WW8 instead.

An additional filter that may kick in is MS Word 2003 XML: this is
avoided by requiring "preferred".

Change-Id: I46e280beb5341213b0fe7a09a549b52c0c1ea3f6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/127219
Reviewed-by: Miklos Vajna <vmiklos@collabora.com>
Tested-by: Jenkins

3 files changed, 24 insertions, 1 deletions

diff --git a/filter/qa/unit/data/empty.doc b/filter/qa/unit/data/empty.doc
new file mode 100644
index 000000000000..e69de29bb2d1
--- /dev/null
+++ b/filter/qa/unit/data/empty.doc
diff --git a/filter/qa/unit/textfilterdetect.cxx b/filter/qa/unit/textfilterdetect.cxx
index 95c2b7697159..62d0d60a23a7 100644
--- a/filter/qa/unit/textfilterdetect.cxx
+++ b/filter/qa/unit/textfilterdetect.cxx
@@ -112,6 +112,25 @@ CPPUNIT_TEST_FIXTURE(TextFilterDetectTest, testEmptyFile)
     // Writer instead.
     CPPUNIT_ASSERT(xServiceInfo->supportsService("com.sun.star.presentation.PresentationDocument"));
     getComponent()->dispose();
+
+    // ... and DOC
+    aURL = m_directories.getURLFromSrc(DATA_DIRECTORY) + "empty.doc";
+    // Without the accompanying fix in place, this test would have failed, the import filter aborted
+    // loading.
+    getComponent() = loadFromDesktop(aURL);
+    xServiceInfo.set(getComponent(), uno::UNO_QUERY);
+    CPPUNIT_ASSERT(xServiceInfo.is());
+    CPPUNIT_ASSERT(xServiceInfo->supportsService("com.sun.star.text.TextDocument"));
+    uno::Reference<frame::XModel> xModel(getComponent(), uno::UNO_QUERY);
+    uno::Sequence<beans::PropertyValue> aArgs = xModel->getArgs();
+    comphelper::SequenceAsHashMap aMap(aArgs);
+    OUString aFilterName;
+    aMap["FilterName"] >>= aFilterName;
+    // Without the accompanying fix in place, this test would have failed with:
+    // - Expected: MS Word 97
+    // - Actual  : MS WinWord 6.0
+    // i.e. opening worked, but saving back failed instead of producing a WW8 binary file.
+    CPPUNIT_ASSERT_EQUAL(OUString("MS Word 97"), aFilterName);
 }
 }
 
diff --git a/filter/source/textfilterdetect/filterdetect.cxx b/filter/source/textfilterdetect/filterdetect.cxx
index 22db169b36e5..f8fc5cb865eb 100644
--- a/filter/source/textfilterdetect/filterdetect.cxx
+++ b/filter/source/textfilterdetect/filterdetect.cxx
@@ -148,7 +148,11 @@ bool HandleEmptyFileUrlByExtension(MediaDescriptor& rMediaDesc, const OUString&
         return false;
     }
 
-    std::shared_ptr<const SfxFilter> pFilter(SfxFilterMatcher().GetFilter4Extension(rExt));
+    // Requiring the export+preferred flags helps to find the relevant filter, e.g. .doc -> WW8 (and
+    // not WW6 or Mac_Word).
+    SfxFilterFlags nMust
+        = SfxFilterFlags::IMPORT | SfxFilterFlags::EXPORT | SfxFilterFlags::PREFERED;
+    std::shared_ptr<const SfxFilter> pFilter(SfxFilterMatcher().GetFilter4Extension(rExt, nMust));
     if (!pFilter)
     {
         return false;