fix: add support for nullable arrays in Swift 5,6

[HarelM]

• Fixes [BUG] [SWIFT] Array items cannot be nullable #22355

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CC: @jgavris @ehyche @Edubits @jaz-ah @4brunu @dydus0x14

---

Summary by cubic

Respect nullable array items in Swift 5 and 6 generators. Previously arrays and sets always used non-optional element types; now when item schemas are nullable, elements are optional (e.g., [String?], Set<String?>). Fixes #22355.

• Affected generators: Swift5ClientCodegen, Swift6ClientCodegen; non-nullable items are unchanged.
• Detects nullability via nullable: true, x-nullable, and aliased schemas, including nested arrays and sets.
• Update call sites to handle nil elements; decoding arrays containing null now succeeds.

^{Written for commit 5189517. Summary will update on new commits.}

[cubic-dev-ai]

All reported issues were addressed across 6 files

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

2 issues found across 6 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java:783">
P2: Nullable array items that are `$ref`s to an enum, composed, or object model are never marked Optional. `unaliasSchema` deliberately returns the ref unchanged for enum/composed/model refs, so `isNullable` on its result is always false there, and the item loses the `?` even when the referenced schema declares `nullable: true` (or X-NULLABLE). The added test only covers an aliased primitive (`NullableString -> [String?]`). Resolve the referenced schema for the nullability check instead of relying on `unaliasSchema` when `items` carries a `$ref`.</violation>
</file>

<file name="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java">

<violation number="1" location="modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java:829">
P2: When an array item is a `$ref` to a nullable object model, `unaliasSchema(items)` preserves the `$ref`, so `isNullable` never sees the referenced model's `nullable: true` and the generated Swift element type remains non-optional. Check the referenced schema's nullability as well as the unaliased item schema.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Nullable array items that are $refs to an enum, composed, or object model are never marked Optional. unaliasSchema deliberately returns the ref unchanged for enum/composed/model refs, so isNullable on its result is always false there, and the item loses the ? even when the referenced schema declares nullable: true (or X-NULLABLE). The added test only covers an aliased primitive (NullableString -> [String?]). Resolve the referenced schema for the nullability check instead of relying on unaliasSchema when items carries a $ref.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift5ClientCodegen.java, line 783:

<comment>Nullable array items that are `$ref`s to an enum, composed, or object model are never marked Optional. `unaliasSchema` deliberately returns the ref unchanged for enum/composed/model refs, so `isNullable` on its result is always false there, and the item loses the `?` even when the referenced schema declares `nullable: true` (or X-NULLABLE). The added test only covers an aliased primitive (`NullableString -> [String?]`). Resolve the referenced schema for the nullability check instead of relying on `unaliasSchema` when `items` carries a `$ref`.</comment>

<file context>
@@ -780,7 +780,7 @@ public String getTypeDeclaration(Schema p) {
     private String getItemsTypeDeclaration(Schema items) {
         String itemsTypeDeclaration = getTypeDeclaration(items);
-        String nullable = items.getNullable() != null && items.getNullable() && !itemsTypeDeclaration.endsWith("?") ? "?" : "";
+        String nullable = ModelUtils.isNullable(unaliasSchema(items)) && !itemsTypeDeclaration.endsWith("?") ? "?" : "";
         return itemsTypeDeclaration + nullable;
     }
</file context>

[cubic-dev-ai]

P2: When an array item is a $ref to a nullable object model, unaliasSchema(items) preserves the $ref, so isNullable never sees the referenced model's nullable: true and the generated Swift element type remains non-optional. Check the referenced schema's nullability as well as the unaliased item schema.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/Swift6ClientCodegen.java, line 829:

<comment>When an array item is a `$ref` to a nullable object model, `unaliasSchema(items)` preserves the `$ref`, so `isNullable` never sees the referenced model's `nullable: true` and the generated Swift element type remains non-optional. Check the referenced schema's nullability as well as the unaliased item schema.</comment>

<file context>
@@ -826,7 +826,7 @@ public String getTypeDeclaration(Schema p) {
     private String getItemsTypeDeclaration(Schema items) {
         String itemsTypeDeclaration = getTypeDeclaration(items);
-        String nullable = items.getNullable() != null && items.getNullable() && !itemsTypeDeclaration.endsWith("?") ? "?" : "";
+        String nullable = ModelUtils.isNullable(unaliasSchema(items)) && !itemsTypeDeclaration.endsWith("?") ? "?" : "";
         return itemsTypeDeclaration + nullable;
     }
</file context>

Suggested change

	String nullable = ModelUtils.isNullable(unaliasSchema(items)) && !itemsTypeDeclaration.endsWith("?") ? "?" : "";
	String nullable = (ModelUtils.isNullable(unaliasSchema(items)) || ModelUtils.isNullable(ModelUtils.getReferencedSchema(openAPI, items))) && !itemsTypeDeclaration.endsWith("?") ? "?" : "";