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fix: consume implicit one-or-more placeholder in add #395

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Merged
webern merged 1 commit into from
Aug 15, 2026
Merged

fix: consume implicit one-or-more placeholder in add #395

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16 changes: 13 additions & 3 deletions src/private/mx/core/OneOrMore.h
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Original file line number Diff line number Diff line change
Expand Up @@ -20,11 +20,11 @@ namespace mx::core
template <typename T> class OneOrMore
{
public:
OneOrMore() : m_items(1)
OneOrMore() : m_items(1), m_hasPlaceholder(true)
{
}

explicit OneOrMore(T first)
explicit OneOrMore(T first) : m_hasPlaceholder(false)
{
m_items.push_back(std::move(first));
}
Expand All @@ -41,12 +41,21 @@ template <typename T> class OneOrMore

void add(T item)
{
m_items.push_back(std::move(item));
if (m_hasPlaceholder)
{
m_items.front() = std::move(item);
m_hasPlaceholder = false;
}
else
{
m_items.push_back(std::move(item));
}
}

/// Deterministic repair: an empty replacement becomes one default item.
void setItems(std::vector<T> items)
{
m_hasPlaceholder = items.empty();
if (items.empty())
{
items.emplace_back();
Expand All @@ -66,6 +75,7 @@ template <typename T> class OneOrMore

private:
std::vector<T> m_items;
bool m_hasPlaceholder = false;
};

} // namespace mx::core
31 changes: 31 additions & 0 deletions src/private/mxtest/core/ShapeTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@
#include "cpul/cpulTestHarness.h"

#include "mx/core/Error.h"
#include "mx/core/OneOrMore.h"
#include "mx/core/Xml.h"
#include "mx/core/generated/Beam.h"
#include "mx/core/generated/BeamValue.h"
Expand Down Expand Up @@ -88,6 +89,36 @@ TEST(DefaultConstructionIsValid, Shapes)
CHECK_EQUAL(std::string{"<pitch><step>A</step><octave>0</octave></pitch>"}, toXml(Pitch{}));
}

TEST(OneOrMoreAddConsumesDefaultPlaceholder, Shapes)
{
OneOrMore<int> items;
items.add(7);
CHECK_EQUAL(std::size_t{1}, items.items().size());
CHECK_EQUAL(7, items.front());

items.add(8);
CHECK_EQUAL(std::size_t{2}, items.items().size());
CHECK_EQUAL(8, items.items().back());
}

TEST(OneOrMoreAddPreservesExplicitFirstItem, Shapes)
{
OneOrMore<int> items{0};
items.add(7);
CHECK_EQUAL(std::size_t{2}, items.items().size());
CHECK_EQUAL(0, items.items().front());
CHECK_EQUAL(7, items.items().back());
}

TEST(OneOrMoreEmptySetItemsCreatesPlaceholder, Shapes)
{
OneOrMore<int> items{1};
items.setItems({});
items.add(7);
CHECK_EQUAL(std::size_t{1}, items.items().size());
CHECK_EQUAL(7, items.front());
}

TEST(VariantExclusivity, Shapes)
{
// Exactly one alternative by construction; duplicate alternative TYPES
Expand Down
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