feat: PoC for dynamic constraints using standard cds views

bookshop/server.js

@@ -0,0 +1,26 @@
+//
+//  Quick and dirty implementation for cds.validate() using db-level constraints
+//
+
+const cds = require('@sap/cds')
+cds.on('served', ()=> {
+
+  const $ = cds.validate; cds.validate = async function (entity, key, ...columns) {
+    if (!entity.is_entity) return $(...arguments)
+    if (entity.constraints) entity = entity.constraints
+    if (key?.results) key = key.results[0].lastInsertRowid
+    const checks = await SELECT.one.from (entity, key, columns.length && columns)
+    const failed = {}; for (let c in checks) {
+      if (c in entity.keys) continue
+      if (c[0] == '_') continue
+      if (checks[c]) failed[c] = checks[c]
+    }
+    if (Object.keys(failed).length) throw cds.error `Invalid input: ${failed}`
+  }
+
+})
+
+Object.defineProperties (cds.entity.prototype, {
+  constraints: { get() { return cds.model.definitions[this.name+'.constraints'] }},
+  fields: { get() { return cds.model.definitions[this.name+'.field.control'] }},
+})