Relax when assigning struct[] or union[] of similar

Attempt copy with partial assignment.

src/data.cpp

@@ -619,15 +619,28 @@ void Value::copyIn(const void *ptr, StoreType type)
                 // assign array of Struct/Union/Any
                 auto tsrc  = src.castTo<const Value>();
 
+                bool convert = false;
                 if(desc->code!=TypeCode::AnyA) {
                     // enforce member type for Struct[] and Union[]
                     for(auto& val : tsrc) {
                         if(val.desc && val.desc!=desc->members.data()) {
-                            throw NoConvert(SB()<<"Unable to assign "<<desc->code<<" with "<<type);
+                            convert = true;
+                            break;
                         }
                     }
+                    if(convert) {
+                        shared_array<Value> scratch(tsrc.size());
+                        for(auto i : range(tsrc.size())) {
+                            if(tsrc[i]) {
+                                scratch[i] = allocMember();
+                                scratch[i].assign(tsrc[i]);
+                            }
+                        }
+                        dest = scratch.freeze().castTo<const void>();
+                    }
                 }
-                dest = src;
+                if(!convert)
+                    dest = src;
 
             } else if(src.original_type()!=ArrayType::Value && uint8_t(desc->code.code)==uint8_t(src.original_type())) {
                 // assign array of scalar w/o convert
@@ -676,7 +689,7 @@ void Value::copyIn(const void *ptr, StoreType type)
                 for(auto i : range(desc->miter.size())) {
                     auto idx(desc->miter[i].second);
 
-                    if(src.desc!=&desc->members[idx])
+                    if(!_equal(src.desc, &desc->members[idx]))
                         continue;
 
                     std::shared_ptr<const FieldDesc> udesc(store->top->desc, &desc->members[idx]);

test/testdata.cpp

@@ -358,6 +358,56 @@ void testAssignSimilar()
     }
 }
 
+void testAssignSimilarNDArray()
+{
+    testShow()<<__func__;
+
+    Value val1, val2;
+    using namespace pvxs::members;
+    {
+        auto def(nt::NTNDArray{}.build());
+        def += {
+                StructA("dimensions", {
+                            Int32("val1"),
+                        }),
+        };
+        val1 = def.create();
+    }
+    {
+        auto def(nt::NTNDArray{}.build());
+        def += {
+                StructA("dimensions", {
+                            Int32("val2"),
+                        }),
+        };
+        val2 = def.create();
+    }
+
+    testFalse(val1.equalType(val2));
+    testTrue(val1["dimension"].equalType(val2["dimension"]));
+
+    val1.from(val2); // nothing marked, so a no-op
+
+    shared_array<const uint8_t> pixels({1,2,3,4,5,6});
+    val1["value->ubyteValue"] = pixels;
+    shared_array<Value> dims;//(2);
+    dims.resize(2);
+    dims[0] = val1["dimension"].allocMember()
+            .update("size", 12);
+    dims[1] = dims[0].cloneEmpty()
+            .update("size", 34);
+    val1["dimension"] = dims.freeze();
+
+    val2.from(val1);
+
+    testTrue(val2["value"].isMarked(false,false));
+    testTrue(val2["dimension"].isMarked(false,false));
+    testFalse(val2["timeStamp"].isMarked(true, true));
+    testArrEq(pixels, val2["value"].as<shared_array<const uint8_t>>());
+    testEq(val2["dimension[0].size"].as<uint32_t>(), 12u);
+    testEq(val2["dimension[1].size"].as<uint32_t>(), 34u);
+}
+
 void testUnionMagicAssign()
 {
     testShow()<<__func__;
@@ -445,7 +495,7 @@ void testClear()
 
 MAIN(testdata)
 {
-    testPlan(148);
+    testPlan(156);
     testSetup();
     testTraverse();
     testAssign();
@@ -496,6 +546,7 @@ MAIN(testdata)
     testConvertScalar2<int32_t, uint64_t, int64_t>(0, 0x100000000llu, -0);
 
     testAssignSimilar();
+    testAssignSimilarNDArray();
     testUnionMagicAssign();
     testExtract();
     testClear();