fix: report a duplicate name instead of failing the page

Adding a category or project whose name exists, or renaming an item onto an
existing name, hit the unique constraint and rendered SvelteKit's 500 page.
Translate SQLITE_CONSTRAINT_UNIQUE into a form error on the three forms.

1 files changed, 13 insertions, 0 deletions

diff --git a/src/lib/server/db/errors.ts b/src/lib/server/db/errors.ts
new file mode 100644
index 0000000..4b101f8
--- /dev/null
+++ b/src/lib/server/db/errors.ts
@@ -0,0 +1,13 @@
+/**
+ * True when the failure is SQLite's UNIQUE constraint. Drizzle wraps driver
+ * errors, so the libsql error sits at some depth of the `cause` chain.
+ */
+export function isUniqueViolation(error: unknown): boolean {
+	let current: unknown = error;
+	while (current instanceof Error) {
+		if ('code' in current && current.code === 'SQLITE_CONSTRAINT_UNIQUE')
+			return true;
+		current = current.cause;
+	}
+	return false;
+}