fix: do not write divisions in scores with no notes

src/include/mx/api/ScoreData.h

@@ -79,6 +79,12 @@ class ScoreData
     DefaultsData defaults;
     std::vector<PartData> parts;
     std::vector<PartGroupData> partGroups;
+
+    /// The score's time resolution: how many `tickTimePosition`/duration ticks make up one
+    /// quarter note. Corresponds to the `<divisions>` MusicXML element. Choose a value with
+    /// enough factors for the durations you need (the default accommodates tuplets through
+    /// septuplets). Zero means the score has no time resolution at all — no durations exist
+    /// anywhere — and no `<divisions>` is written.
     int ticksPerQuarter;
 
     /// Specifies page breaks, system breaks, and changes to system and page layout. Global/default page and

src/private/mx/impl/MeasureWriter.cpp

@@ -117,7 +117,13 @@ void MeasureWriter::writeMeasureGlobals()
 
     if (myHistory.getCursor().isFirstMeasureInPart)
     {
-        myPropertiesWriter->writeDivisions(myHistory.getCursor().getGlobalTicksPerQuarter());
+        // A score with no time resolution (ticksPerQuarter <= 0: the source declared no
+        // <divisions> and contains no durations) must not have one invented for it; writing
+        // 0 here would be clamped to a bogus positive value by core::PositiveDivisions.
+        if (myHistory.getCursor().getGlobalTicksPerQuarter() > 0)
+        {
+            myPropertiesWriter->writeDivisions(myHistory.getCursor().getGlobalTicksPerQuarter());
+        }
 
         if (myMeasureData.staves.size() > 1)
         {

src/private/mxtest/api/roundtrip-baseline.txt

@@ -350,3 +350,51 @@ rpatters1/timesigs_composite-ref.musicxml
 # the serialized stream once voice 1 is written ahead of voice 2, plus a wedge.
 # Pins explicit slur/wedge numbers surviving read -> write -> read verbatim.
 rpatters1/slurs_overbars.musicxml
+
+# Unblocked by the spurious-divisions fix: a score whose source declares no
+# <divisions> anywhere (and has no durations) reads as ticksPerQuarter = 0,
+# and the writer used to invent <attributes><divisions>0.000001</divisions>
+# for the first measure of every part (LCM of an empty set = 0, clamped to a
+# bogus positive by core::PositiveDivisions). The writer now omits <divisions>
+# when the score has no time resolution.
+lysuite/ly51b_Header_Quotes.xml
+mjbsuite/HasMusicXmlVersionFalse.xml
+mjbsuite/HasMusicXmlVersionTrue.xml
+synthetic/beat-type.3.0.xml
+synthetic/beats.3.0.xml
+synthetic/bracket.3.0.xml
+synthetic/dashes.3.0.xml
+synthetic/encoding-description.3.0.xml
+synthetic/first.4.0.xml
+synthetic/group.3.0.xml
+synthetic/instrument-abbreviation.3.0.xml
+synthetic/instrument-name.3.0.xml
+synthetic/instrument-sound-enum.3.0.xml
+synthetic/interchangeable.3.0.xml
+synthetic/lyric-font.3.0.xml
+synthetic/miscellaneous-field.3.0.xml
+synthetic/movement-number.3.0.xml
+synthetic/movement-title.3.0.xml
+synthetic/music-font.3.0.xml
+synthetic/n.3.1.xml
+synthetic/numeral-fifths.4.0.xml
+synthetic/numeral-mode.4.0.xml
+synthetic/numeral.4.0.xml
+synthetic/other-dynamics.3.0.xml
+synthetic/pf.3.1.xml
+synthetic/second.4.0.xml
+synthetic/senza-misura.3.0.xml
+synthetic/sfzp.3.1.xml
+synthetic/software.3.0.xml
+synthetic/staff-size.4.0.xml
+synthetic/straight.4.0.xml
+synthetic/swing-style.4.0.xml
+synthetic/swing-type.4.0.xml
+synthetic/swing.4.0.xml
+synthetic/time-relation.3.0.xml
+synthetic/virtual-library.3.0.xml
+synthetic/virtual-name.3.0.xml
+synthetic/voice.3.0.xml
+synthetic/word-font.3.0.xml
+synthetic/work-number.3.0.xml
+synthetic/work-title.3.0.xml

src/private/mxtest/impl/MeasureWriterTest.cpp

@@ -224,6 +224,55 @@ TEST(PropertiesButNoNotes, MeasureWriter)
 
 T_END
 
+TEST(ZeroTicksPerQuarterWritesNoDivisions, MeasureWriter)
+{
+    // A score with no time resolution (ticksPerQuarter == 0, e.g. a source that declared no
+    // <divisions> and has no durations) must not have a bogus <divisions> invented for it.
+    mxtest::TestParameters params;
+    params.ticksPerQuarter = 0;
+    params.measureIndex = 0;
+    params.partIndex = 0;
+    params.numStaves = 1;
+    mxtest::TestItems t = mxtest::setupTestItems(params);
+
+    const auto partwiseMeasure = t.measureWriter->getPartwiseMeasure();
+    CHECK(partwiseMeasure.musicData().empty());
+}
+
+T_END
+
+TEST(ZeroTicksPerQuarterKeepsOtherProperties, MeasureWriter)
+{
+    // With ticksPerQuarter == 0 the <attributes> element is still written when it has real
+    // content (here a clef); only the <divisions> child is suppressed.
+    mxtest::TestParameters params;
+    params.ticksPerQuarter = 0;
+    params.measureIndex = 0;
+    params.partIndex = 0;
+    params.numStaves = 1;
+    mxtest::TestItems t = mxtest::setupTestItems(params);
+    auto &staff = t.measureData->staves.at(0);
+    staff.clefs.emplace_back(api::ClefData{});
+    auto &clef = staff.clefs.back();
+    clef.symbol = api::ClefSymbol::g;
+    clef.line = 2;
+
+    const auto partwiseMeasure = t.measureWriter->getPartwiseMeasure();
+    auto musicData = partwiseMeasure.musicData();
+    auto mdcIter = musicData.begin();
+    auto mdcEnd = musicData.end();
+
+    CHECK(mdcIter != mdcEnd);
+    CHECK(mdcIter->isAttributes());
+    const auto &props = mdcIter->asAttributes();
+    CHECK(!props.divisions().has_value());
+    CHECK_EQUAL(1, props.clef().size());
+
+    CHECK(++mdcIter == mdcEnd);
+}
+
+T_END
+
 TEST(MultiStaffClefKeepsNumber, MeasureWriter)
 {
     // Counterpart to PropertiesButNoNotes: in a multi-staff part the clef number is required