From 9d6f52dcdd745fd6bc52505e4abf9f33cfbb484f Mon Sep 17 00:00:00 2001
From: Aleksei Menshutin <a.menshutin@vkteam.ru>
Date: Sun, 4 Oct 2026 23:11:39 +0300
Subject: [PATCH] [TS] Lock the rest-parameter caller packing contract (#373)

---
 .../ets/test/EtsTsArrayParameterTest.kt       | 11 ++++++
 jacodb-ets/ts-frontend/src/dto/signatures.ts  |  1 +
 .../ts-frontend/test/rest-parameters.spec.ts  | 38 +++++++++++++++++++
 3 files changed, 50 insertions(+)
 create mode 100644 jacodb-ets/ts-frontend/test/rest-parameters.spec.ts

diff --git a/jacodb-ets/src/test/kotlin/org/jacodb/ets/test/EtsTsArrayParameterTest.kt b/jacodb-ets/src/test/kotlin/org/jacodb/ets/test/EtsTsArrayParameterTest.kt
index f145df058..3a7865815 100644
--- a/jacodb-ets/src/test/kotlin/org/jacodb/ets/test/EtsTsArrayParameterTest.kt
+++ b/jacodb-ets/src/test/kotlin/org/jacodb/ets/test/EtsTsArrayParameterTest.kt
@@ -73,4 +73,15 @@ class EtsTsArrayParameterTest {
 
         assertTrue(method.cfg.stmts.any { it is EtsIfStmt })
     }
+
+    @Test
+    fun `rest parameter metadata survives frontend JSON and model conversion`() {
+        val dto = roundTrip("export function count(...values: number[]): number { return values.length; }")
+
+        val dtoMethod = dto.classes.flatMap { it.methods }.single { it.signature.name == "count" }
+        val method = dto.toEtsFile().classes.flatMap { it.methods }.single { it.name == "count" }
+
+        assertTrue(dtoMethod.signature.parameters.single().isRest)
+        assertTrue(method.signature.parameters.single().isRest)
+    }
 }
diff --git a/jacodb-ets/ts-frontend/src/dto/signatures.ts b/jacodb-ets/ts-frontend/src/dto/signatures.ts
index be55104e0..dcdaa02a8 100644
--- a/jacodb-ets/ts-frontend/src/dto/signatures.ts
+++ b/jacodb-ets/ts-frontend/src/dto/signatures.ts
@@ -52,6 +52,7 @@ export interface MethodParameterDto {
     name: string;
     type: TypeDto;
     isOptional?: boolean; // Kotlin default: false
+    /** Call consumers pack trailing raw arguments into the array read by ParameterRef. */
     isRest?: boolean; // Kotlin default: false
 }
 
diff --git a/jacodb-ets/ts-frontend/test/rest-parameters.spec.ts b/jacodb-ets/ts-frontend/test/rest-parameters.spec.ts
new file mode 100644
index 000000000..6c2d6af53
--- /dev/null
+++ b/jacodb-ets/ts-frontend/test/rest-parameters.spec.ts
@@ -0,0 +1,38 @@
+import { describe, expect, it } from "vitest";
+import { consumers } from "./array-test-consumers";
+import { lower, methodByName } from "./util";
+import { serializeEtsFile } from "../src/serialize";
+
+describe("rest parameter caller contract", () => {
+    it("keeps isRest through JSON and uses it for calls with zero and multiple raw arguments", () => {
+        const source = "function count(...values: number[]): number { return values.length; }";
+        const { file, diagnostics } = lower(source);
+        const roundTripped = JSON.parse(serializeEtsFile(file));
+        const method = methodByName(roundTripped, "count");
+        const { ir, native } = consumers(source, "count");
+
+        expect(diagnostics.messages).toEqual([]);
+        expect(method.signature.parameters).toHaveLength(1);
+        expect(method.signature.parameters[0].isRest).toBe(true);
+        for (const args of [[], [1], [1, 2]]) {
+            expect(ir(...args)).toBe(native(...args));
+            expect(ir(...args)).toBe(args.length);
+        }
+    });
+
+    it("passes raw arguments through frontend calls to the packing consumer", () => {
+        const source = "function count(first: number, ...rest: number[]) { return rest.length; } function invoke() { return count(1, 2, 3); }";
+        const { ir, native } = consumers(source, "invoke");
+
+        expect(ir()).toBe(native());
+        expect(ir()).toBe(2);
+    });
+
+    it("packs remaining raw arguments in order, including missing normal arguments", () => {
+        const { ir, native } = consumers("function f(first: number, ...rest: number[]) { return rest; }", "f");
+
+        for (const args of [[], [1], [1, 2], [1, 2, 3]]) {
+            expect(ir(...args)).toEqual(native(...args));
+        }
+    });
+});