fix: preserve source locale when duplicating content (#2303)

duplicate() built the copy's slug against the source row's locale but
inserted the row without one, so create()'s fallback landed every copy
in 'en'. On locale-scoped admin lists the copy silently vanished, and
the mis-scoped slug-uniqueness check could trip the UNIQUE(slug, locale)
constraint when the generated slug already existed in 'en'.

Pass the source locale through to create(). Duplicates keep their own
fresh translation group — a copy is a new entry, not a translation —
which create() already does by default; a test now locks that in.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: edrpls

.changeset/duplicate-preserves-locale.md

@@ -0,0 +1,5 @@
+---
+"emdash": patch
+---
+
+Fixes the Duplicate action creating the copy in the default locale instead of the source entry's locale. Duplicates of non-English entries now stay in their locale — so they appear in the locale-filtered admin list they were duplicated from — and no longer fail with a unique-constraint error when the generated slug already exists in the default locale.

packages/core/src/database/repositories/content.ts

@@ -322,6 +322,7 @@ export class ContentRepository {
 			data: newData,
 			status: "draft",
 			authorId: authorId || original.authorId || undefined,
+			locale: original.locale ?? undefined,
 		});
 	}
 

packages/core/tests/integration/i18n/i18n.test.ts

@@ -189,6 +189,53 @@ describe("i18n (Integration)", () => {
 			).rejects.toThrow();
 		});
 
+		// ── duplicate ─────────────────────────────────────────────────
+
+		it("duplicate() preserves the source item's locale", async () => {
+			const original = await repo.create(
+				createPostFixture({ slug: "hola-mundo", locale: "es", data: { title: "Hola Mundo" } }),
+			);
+
+			const copy = await repo.duplicate("post", original.id);
+
+			expect(copy.locale).toBe("es");
+		});
+
+		it("duplicate() assigns a fresh translation group", async () => {
+			const enPost = await repo.create(createPostFixture({ slug: "hello", locale: "en" }));
+			const esPost = await repo.create(
+				createPostFixture({
+					slug: "hola",
+					locale: "es",
+					translationOf: enPost.id,
+					data: { title: "Hola" },
+				}),
+			);
+
+			const copy = await repo.duplicate("post", esPost.id);
+
+			expect(copy.translationGroup).toBe(copy.id);
+			expect(copy.translationGroup).not.toBe(esPost.translationGroup);
+		});
+
+		it("duplicate() does not collide with the generated slug in another locale", async () => {
+			await repo.create(
+				createPostFixture({
+					slug: "hola-mundo-copy",
+					locale: "en",
+					data: { title: "Unrelated EN Post" },
+				}),
+			);
+			const original = await repo.create(
+				createPostFixture({ slug: "hola-mundo", locale: "es", data: { title: "Hola Mundo" } }),
+			);
+
+			const copy = await repo.duplicate("post", original.id);
+
+			expect(copy.locale).toBe("es");
+			expect(copy.slug).toBe("hola-mundo-copy");
+		});
+
 		// ── findBySlug ────────────────────────────────────────────────
 
 		it("findBySlug() without locale returns any match", async () => {