Fix swizzle edge cases in version upgrade

source/MaterialXCore/Version.cpp

@@ -992,10 +992,21 @@ void Document::upgradeVersion()
             { "color3", 3 }, { "color4", 4 },
             { "vector2", 2 }, { "vector3", 3 }, { "vector4", 4 }
         };
-        const StringSet CHANNEL_CONVERT_PATTERNS =
+
+        // Pairs of channels string & source channel count.
+        // Source channel count is needed to filter out multi-channel inputs when only the first channel is being used.
+        const vector<std::pair<std::string, size_t>> CHANNEL_CONVERT_PATTERNS =
+        {
+            { { "rgb", 3 }, { "rgb", 4 }, { "rgba", 4 }, { "xyz", 3 }, { "xyz", 4 }, { "xyzw", 4 }, { "rrr", 1 }, { "xxx", 1 }, { "rr", 1 }, { "xx", 1 } }
+        };
+        auto matchesConvertPattern = [&](const string& channels, size_t sourceChannelCount)
         {
-            "rgb", "rgba", "xyz", "xyzw", "rrr", "xxx"
+            for (auto& pattern : CHANNEL_CONVERT_PATTERNS)
+                if (pattern == std::make_pair(channels, sourceChannelCount))
+                    return true;
+            return false;
         };
+
         const vector<std::pair<StringSet, string>> CHANNEL_ATTRIBUTE_PATTERNS =
         {
             { { "xx", "xxx", "xxxx" }, "float" },
@@ -1169,8 +1180,10 @@ void Document::upgradeVersion()
                     CHANNEL_COUNT_MAP.count(node->getType()))
                 {
                     string channelString = channelsInput ? channelsInput->getValueString() : EMPTY_STRING;
-                    size_t sourceChannelCount = CHANNEL_COUNT_MAP.at(inInput->getType());
-                    size_t destChannelCount = CHANNEL_COUNT_MAP.at(node->getType());
+                    string sourceType = inInput->getType();
+                    string destType = node->getType();
+                    size_t sourceChannelCount = CHANNEL_COUNT_MAP.at(sourceType);
+                    size_t destChannelCount = CHANNEL_COUNT_MAP.at(destType);
 
                     // Resolve the invalid case of having both a connection and a value
                     // by removing the value attribute.
@@ -1228,7 +1241,7 @@ void Document::upgradeVersion()
                             node->setInputValue("index", (int) CHANNEL_INDEX_MAP.at(channelString[0]));
                         }
                     }
-                    else if (CHANNEL_CONVERT_PATTERNS.count(channelString))
+                    else if (sourceType != destType && matchesConvertPattern(channelString, sourceChannelCount))
                     {
                         // Replace swizzle with convert.
                         node->setCategory("convert");

source/MaterialXTest/MaterialXCore/Version.cpp

@@ -0,0 +1,88 @@
+//
+// Copyright Contributors to the MaterialX Project
+// SPDX-License-Identifier: Apache-2.0
+//
+
+#include <MaterialXTest/External/Catch/catch.hpp>
+
+#include <MaterialXCore/Util.h>
+#include <MaterialXCore/Document.h>
+#include <MaterialXFormat/XmlIo.h>
+#include <MaterialXFormat/Util.h>
+
+// TODO: move to format/ ?
+
+namespace mx = MaterialX;
+
+const char* swizzleDoc1 = R"(
+<?xml version="1.0"?>
+<materialx version="1.38">
+  <constant name="f" type="float">
+    <input name="value" type="float" value="0" />
+  </constant>
+  <constant name="v2" type="vector2">
+    <input name="value" type="vector2" value="0, 0" />
+  </constant>
+  <constant name="v3" type="vector3">
+    <input name="value" type="vector3" value="0, 0, 0" />
+  </constant>
+  <constant name="v4" type="vector4">
+    <input name="value" type="vector4" value="0, 0, 0, 1" />
+  </constant>
+
+  <swizzle name="xyz_to_xyz" type="vector3">
+    <input name="in" type="vector3" nodename="v3" />
+    <input name="channels" type="string" value="xyz" />
+  </swizzle>
+
+  <swizzle name="xyz_to_rgb" type="color3">
+    <input name="in" type="vector3" nodename="v3" />
+    <input name="channels" type="string" value="xyz" />
+  </swizzle>
+
+  <swizzle name="xy_to_xxx" type="vector3">
+    <input name="in" type="vector2" nodename="v2" />
+    <input name="channels" type="string" value="xxx" />
+  </swizzle>
+
+  <swizzle name="x_to_xxx" type="vector3">
+    <input name="in" type="float" nodename="f" />
+    <input name="channels" type="string" value="xxx" />
+  </swizzle>
+</materialx>
+)";
+
+TEST_CASE("Handling 1.38 swizzle nodes", "[version]")
+{
+    mx::DocumentPtr libs = mx::createDocument();
+    mx::loadLibraries({ "libraries" }, mx::getDefaultDataSearchPath(), libs);
+
+    auto doc = mx::createDocument();
+    doc->importLibrary(libs);
+    mx::readFromXmlBuffer(doc, swizzleDoc1);
+    doc->validate();
+
+    struct ExpectedNodes
+    {
+        std::string name;
+        std::string category;
+        std::string nodeDefName;
+    };
+
+    ExpectedNodes expectedNodes[] = {
+        { "xyz_to_xyz", "combine3", "ND_combine3_vector3" },
+        { "xyz_to_rgb", "convert", "ND_convert_vector3_color3" },
+        { "xy_to_xxx", "combine3", "ND_combine3_vector3" },
+        { "x_to_xxx", "convert", "ND_convert_float_vector3" },
+    };
+
+    for (auto& expected : expectedNodes)
+    {
+        auto node = doc->getNode(expected.name);
+        REQUIRE(node);
+        REQUIRE(node->getCategory() == expected.category);
+        auto nodeDef = node->getNodeDef();
+        REQUIRE(nodeDef);
+        REQUIRE(nodeDef->getName() == expected.nodeDefName);
+    }
+}