fix(swift): honor --acronym-style for leading acronyms

packages/quicktype-core/src/language/Swift/utils.ts

@@ -69,7 +69,7 @@ export function swiftNameStyle(
         legalizeName,
         isUpper ? firstUpperWordStyle : allLowerWordStyle,
         firstUpperWordStyle,
-        isUpper ? allUpperWordStyle : allLowerWordStyle,
+        isUpper ? acronymsStyle : allLowerWordStyle,
         acronymsStyle,
         "",
         isStartCharacter,

test/unit/swift-acronym-names.test.ts

@@ -0,0 +1,45 @@
+// The fixture harness cannot catch acronym casing in Swift type names: the
+// generated identifiers are self-consistent, so the code still compiles and
+// round-trips JSON successfully. Generate Swift directly and assert on the
+// emitted struct declaration instead.
+
+import {
+    InputData,
+    jsonInputForTargetLanguage,
+    quicktype,
+} from "../../packages/quicktype-core/src/index.js";
+import { describe, expect, test } from "vitest";
+
+async function swiftStructName(acronymStyle: string): Promise<string> {
+    const jsonInput = jsonInputForTargetLanguage("swift");
+    await jsonInput.addSource({
+        name: "FaqCoordinate",
+        samples: ['{"x":1,"y":2}'],
+    });
+
+    const inputData = new InputData();
+    inputData.addInput(jsonInput);
+
+    const result = await quicktype({
+        inputData,
+        lang: "swift",
+        rendererOptions: { "acronym-style": acronymStyle },
+    });
+    const output = result.lines.join("\n");
+    const match = output.match(/^struct (\w+): Codable \{$/m);
+
+    // biome-ignore lint/suspicious/noMisplacedAssertion: helper is only called from within tests
+    expect(match, `generated Swift output:\n${output}`).not.toBeNull();
+    return match?.[1] ?? "";
+}
+
+describe("Swift leading acronym casing", () => {
+    test.each([
+        ["original", "FaqCoordinate"],
+        ["pascal", "FAQCoordinate"],
+        ["camel", "FaqCoordinate"],
+        ["lowerCase", "faqCoordinate"],
+    ])("honors acronym-style=%s for struct names", async (acronymStyle, expectedName) => {
+        await expect(swiftStructName(acronymStyle)).resolves.toBe(expectedName);
+    });
+});