fix: joins without columns are rejected

db-service/lib/cqn2sql.js

@@ -207,6 +207,11 @@ class CQN2SQLRenderer {
   SELECT(q) {
     let { from, expand, where, groupBy, having, orderBy, limit, one, distinct, localized, forUpdate, forShareLock } =
       q.SELECT
+
+    if (from?.join && !q.SELECT.columns) {
+      throw new Error('CQN query using joins must specify the selected columns.')
+    }
+
     // REVISIT: When selecting from an entity that is not in the model the from.where are not normalized (as cqn4sql is skipped)
     if (!where && from?.ref?.length === 1 && from.ref[0]?.where) where = from.ref[0]?.where
     let columns = this.SELECT_columns(q)

hana/lib/HANAService.js

@@ -291,6 +291,10 @@ class HANAService extends SQLService {
       this.temporary = this.temporary || []
       this.temporaryValues = this.temporaryValues || []
 
+      if (q.SELECT.from?.join && !q.SELECT.columns) {
+        throw new Error('CQN query using joins must specify the selected columns.')
+      }
+
       const { limit, one, orderBy, expand, columns = ['*'], localized, count, parent } = q.SELECT
 
       const walkAlias = q => {

test/scenarios/bookshop/read.test.js

@@ -255,6 +255,40 @@ describe('Bookshop - Read', () => {
     expect((await cds.db.run(query)).count).to.be.eq(2)
   })
 
+  it('joins without columns are rejected because of conflicts', async () => {
+    const query = {
+      SELECT: {
+        from: {
+          join: 'inner',
+          args: [
+            { ref: ['sap.capire.bookshop.Books'], as: 'b' },
+            { ref: ['sap.capire.bookshop.Authors'], as: 'a' },
+          ],
+          on: [{ ref: ['a', 'ID'] }, '=', { ref: ['b', 'author_ID'] }],
+        },
+      },
+    }
+
+    expect(cds.db.run(query)).to.be.rejectedWith(/Ambiguous wildcard elements/)
+  })
+
+  it('joins without columns are rejected in general', async () => {
+    const query = {
+      SELECT: {
+        from: {
+          join: 'inner',
+          args: [
+            { ref: ['AdminService.RenameKeys'], as: 'rk' },
+            { ref: ['DraftService.DraftEnabledBooks'], as: 'deb' },
+          ],
+          on: [{ ref: ['deb', 'ID'] }, '=', { ref: ['rk', 'foo'] }],
+        },
+      },
+    }
+
+    expect(cds.db.run(query)).to.be.rejectedWith(/joins must specify the selected columns/)
+  })
+
   test('Delete Book', async () => {
     const res = await DELETE('/admin/Books(271)', admin)
     expect(res.status).to.be.eq(204)