Retrieve keys from both flavours of CSN

lib/csn.js

@@ -240,4 +240,4 @@ const isView = entity => entity.query && !entity.projection
  */
 const isUnresolved = entity => entity._unresolved === true
 
-module.exports = { amendCSN, isView, isUnresolved }
+module.exports = { amendCSN, isView, isUnresolved, propagateForeignKeys }

lib/visitor.js

@@ -2,7 +2,7 @@
 
 const util = require('./util')
 
-const { amendCSN, isView, isUnresolved } = require('./csn')
+const { amendCSN, isView, isUnresolved, propagateForeignKeys } = require('./csn')
 // eslint-disable-next-line no-unused-vars
 const { SourceFile, baseDefinitions, Buffer } = require('./file')
 const { FlatInlineDeclarationResolver, StructuredInlineDeclarationResolver } = require('./components/inline')
@@ -63,6 +63,7 @@ class Visitor {
      */
     constructor(csn, options = {}, logger = new Logger()) {
         amendCSN(csn.xtended)
+        propagateForeignKeys(csn.inferred)
         this.options = { ...defaults, ...options }
         this.logger = logger
         this.csn = csn
@@ -130,6 +131,24 @@ class Visitor {
         }
     }
 
+    /**
+     * Retrieves all the keys from an entity.
+     * That is: all keys that are present in both inferred, as well as xtended flavour.
+     * @returns {[string, object][]} array of key name and key element pairs
+     */
+    #keys(name) {
+        // FIXME: this is actually pretty bad, as not only have to propagate keys through
+        // both flavours of CSN (see constructor), but we are now also collecting them from
+        // both flavours and deduplicating them.
+        // xtended contains keys that have been inherited from parents
+        // inferred contains keys from queried entities (thing `entity Foo as select from Bar`, where Bar has keys)
+        // So we currently need them both.
+        return Object.entries({
+            ...this.csn.inferred.definitions[name]?.keys ?? {},
+            ...this.csn.xtended.definitions[name]?.keys ?? {}
+        })
+    }
+
     /**
      * Transforms an entity or CDS aspect into a JS aspect (aka mixin).
      * That is, for an element A we get:
@@ -168,7 +187,7 @@ class Visitor {
                 // lookup in cds.definitions can fail for inline structs.
                 // We don't really have to care for this case, as keys from such structs are _not_ propagated to
                 // the containing entity.
-                for (const [kname, kelement] of Object.entries(this.csn.xtended.definitions[element.target]?.keys ?? {})) {
+                for (const [kname, kelement] of this.#keys(element.target)) {
                     if (this.resolver.getMaxCardinality(element) === 1) {
                         kelement.isRefNotNull = !!element.notNull || !!element.key
                         this.visitElement(`${ename}_${kname}`, kelement, file, buffer)