fix(drizzle): unique field errors were not thrown as ValidationErrors (#15146)

The optimized upsert path in `upsertRow` was not wrapped in the error
handling try/catch block, causing unique constraint violations to throw
raw database errors instead of Payload `ValidationError`s.

**Changes:**

- Created `handleUpsertError.ts` utility to centralize unique constraint
error handling, similar to how db-mongodb as `handleError`
- Wrapped optimized upsert path in error handling
- Added test for unique constraint errors in optimized update path

Author: AlessioGr

packages/drizzle/src/upsertRow/handleUpsertError.ts

@@ -0,0 +1,89 @@
+import type { PayloadRequest } from 'payload'
+
+import { ValidationError } from 'payload'
+
+import type { DrizzleAdapter } from '../types.js'
+
+type HandleUpsertErrorArgs = {
+  adapter: DrizzleAdapter
+  error: unknown
+  id?: number | string
+  req?: Partial<PayloadRequest>
+  tableName: string
+}
+
+/**
+ * Handles unique constraint violation errors from PostgreSQL and SQLite,
+ * converting them to Payload ValidationErrors.
+ * Re-throws non-constraint errors unchanged.
+ */
+export const handleUpsertError = ({
+  id,
+  adapter,
+  error: caughtError,
+  req,
+  tableName,
+}: HandleUpsertErrorArgs): never => {
+  let error: any = caughtError
+  if (typeof caughtError === 'object' && caughtError !== null && 'cause' in caughtError) {
+    error = caughtError.cause
+  }
+
+  // PostgreSQL: 23505, SQLite: SQLITE_CONSTRAINT_UNIQUE
+  if (error?.code === '23505' || error?.code === 'SQLITE_CONSTRAINT_UNIQUE') {
+    let fieldName: null | string = null
+
+    if (error.code === '23505') {
+      // PostgreSQL - extract field name from constraint
+      if (adapter.fieldConstraints?.[tableName]?.[error.constraint]) {
+        fieldName = adapter.fieldConstraints[tableName][error.constraint]
+      } else {
+        const replacement = `${tableName}_`
+        if (error.constraint?.includes(replacement)) {
+          const replacedConstraint = error.constraint.replace(replacement, '')
+          if (replacedConstraint && adapter.fieldConstraints[tableName]?.[replacedConstraint]) {
+            fieldName = adapter.fieldConstraints[tableName][replacedConstraint]
+          }
+        }
+      }
+
+      if (!fieldName && error.detail) {
+        // Extract from detail: "Key (field)=(value) already exists."
+        const regex = /Key \(([^)]+)\)=\(([^)]+)\)/
+        const match: string[] = error.detail.match(regex)
+        if (match && match[1]) {
+          fieldName = match[1]
+        }
+      }
+    } else if (error.code === 'SQLITE_CONSTRAINT_UNIQUE') {
+      // SQLite - extract from message: "UNIQUE constraint failed: table.field"
+      const regex = /UNIQUE constraint failed: ([^.]+)\.([^.]+)/
+      const match: string[] = error.message?.match(regex)
+      if (match && match[2]) {
+        if (adapter.fieldConstraints[tableName]) {
+          fieldName = adapter.fieldConstraints[tableName][`${match[2]}_idx`]
+        }
+        if (!fieldName) {
+          fieldName = match[2]
+        }
+      }
+    }
+
+    throw new ValidationError(
+      {
+        id,
+        errors: [
+          {
+            message: req?.t ? req.t('error:valueMustBeUnique') : 'Value must be unique',
+            path: fieldName,
+          },
+        ],
+        req,
+      },
+      req?.t,
+    )
+  }
+
+  // Re-throw non-constraint errors
+  throw caughtError
+}