fix: generate compilable collection helpers for primitive array fields (#261)

[AndreasIgel]

Fixes#261

Problem

For array fields the processor generates two collection convenience helpers — field(List<E>) (ArrayConversionGenerator) and field(Consumer<ArrayListBuilder<E>>) (ArrayBuilderConsumerGenerator). Both were emitted for any array field, but their bodies were only valid for reference element types:

// for int[] scoresthis.scores = changedValue(scores.toArray(newint[0])); // List<Integer>.toArray needs a reference arraynewArrayListBuilder<>(java.util.List.of(this.scores.value())); // infers List<int[]>, not List<Integer>

Any DTO with a primitive array field produced a builder that did not compile.

Fix

Primitive element types now get explicit boxing/unboxing between the boxed List and the primitive array. Reference element types keep the existing toArray(new E[0]) / List.of(...) paths unchanged, so no generated output changes for String[], Integer[], etc.

The project already depends on Apache Commons Lang3 at runtime (the generated builders already import org.apache.commons.lang3.builder.ToStringBuilder). Its org.apache.commons.lang3.ArrayUtils provides toPrimitive/toObject for all primitive/wrapper array pairs, and java.util.Arrays.asList is used to seed the ArrayListBuilder with boxed values. With the new $label:B template placeholder and a small mapper fix to preserve explicit code-block imports, the generated setter for a field int[] scores becomes:

importjava.util.Arrays;
importorg.apache.commons.lang3.ArrayUtils;
...
publicPrimitiveArrayDtoBuilderscores(List<Integer> scores) {
this.scores = changedValue(ArrayUtils.toPrimitive(scores.toArray(newInteger[0])));
returnthis;
}
publicPrimitiveArrayDtoBuilderscores(Consumer<ArrayListBuilder<Integer>> scoresBuilderConsumer) {
ArrayListBuilder<Integer> builder;
if (this.scores.isSet()) {
builder = newArrayListBuilder<Integer>(Arrays.asList(ArrayUtils.toObject(this.scores.value())));
} else {
builder = newArrayListBuilder<Integer>(Arrays.asList());
}
scoresBuilderConsumer.accept(builder);
this.scores = changedValue(ArrayUtils.toPrimitive(builder.build().toArray(newInteger[0])));
returnthis;
}

Changes

• RoasterMapper — resolveCodeTemplate now resolves $label:B for type placeholders via the existing mapBoxedType.
• BuilderToGenerationTypeMapper — toMethodDto now copies explicit codeBlockImports from the generation-side method code DTO to the rendering-side DTO via Set.addAll(...).
• ArrayConversionGenerator — primitive element types now use ArrayUtils.toPrimitive(list.toArray(new Boxed[0])); reference types unchanged.
• ArrayBuilderConsumerGenerator — all array element types now seed ArrayListBuilder<T> from Arrays.asList(...) (boxed existing array for primitives, or an empty list in the unset case) and convert back with toArray(...); primitive arrays additionally box/unbox via ArrayUtils.
• CustomCollectionTypeTest — new primitiveArrayFields_shouldGenerateCompilableCollectionHelpers covering int[], boolean[] and double[]. Each generated collection-helper method and the build() method is asserted with a single contains block spanning the full method signature and body.

Design note

The builder keeps storing the DTO's own type (TrackedValue<int[]>) and converts at the setter boundary, rather than storing a boxed List<Integer> and unboxing in build(). The list-based helpers are not the only writers of an array field — the plain setter takes int... scores, the supplier setter takes Supplier<int[]>, the copy constructor reads int[] off an existing instance, and Jackson binds against the field type — so boxed storage would need a conversion on each of those paths plus in build(), and would make the builder field's type depend on its element type. There is also no incremental add-per-element method for array fields (AddToCollectionGenerator only applies to parameterized List/Set), so the "avoid repeated reallocation while elements accumulate" argument for boxed storage does not apply here.

Verification

• mvn clean install from the repo root: BUILD SUCCESS for all modules (core, processor, example-custom-generator, example).
• Full processor test suite green; the new test relies on the compile-testing harness actually compiling the generated builder, which is exactly what failed before.
• Generated sources of the example module (checked in under example/generated-example-builder) were regenerated and committed; PersonDtoBuilder now uses Arrays.asList(...) for its String[] nickNames2 consumer helper, matching the new reference-array template.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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