feat: add method to check for collections

- calls XML-RPC method 'hasCollection'
- add positive and negative test as well as one to test the behaviour
  for users with insufficient access rights

components/collections.js

@@ -18,6 +18,11 @@ function read (client, name) {
  return client.promisedMethodCall('getCollectionDesc', [name])
 }
 
+// collection exists?
+function exists (client, name) {
+ return client.promisedMethodCall('hasCollection', [name])
+}
+
 // convenience function
 // throws an exception if and only if
 // the collection exists but cannot be written by the user
@@ -30,5 +35,6 @@ module.exports = {
  remove,
  describe,
  read,
+ exists,
  existsAndCanOpen
 }

spec/tests/collections.js

@@ -6,6 +6,41 @@ const asGuest = Object.assign({},
  { basic_auth: { user: 'guest', pass: 'guest' } }
 )
 
+test('collections.exists', function (t) {
+ const db = connect(envOptions)
+
+ t.test('true for existing collection', async function (st) {
+ try {
+ const result = await db.collections.exists('/db')
+ st.true(result, '/db exists')
+ } catch (e) {
+ st.fail(e)
+ }
+ })
+
+ test('false for non-existing collection', async function (st) {
+ try {
+ const result = await db.collections.exists('/foo')
+ st.false(result, '/foo does not exist')
+ } catch (e) {
+ t.fail(e)
+ }
+ })
+
+ test('throws with insufficient access', async function (st) {
+ try {
+ const dbAsGuest = connect()
+ const result = await dbAsGuest.collections.exists('/db/system/security')
+ st.false(result, 'Guest should not see /db/system/security')
+ } catch (e) {
+ // Guest should not see /db/system/security
+ // because it throws with a PermissionDeniedException
+ // it is obvious the collection exists
+ t.ok(e)
+ }
+ })
+})
+
 test('get collection info', function (t) {
  const db = connect(envOptions)
  db.collections.describe('/db')