Change organization in datasource_by_name

Datasource names can overlap across organizations so that the API returns
only a hit of the current one, hence datasource_by_name needs to switch
to the relevant organization first.

lib/puppet/provider/grafana_datasource/grafana.rb

@@ -52,6 +52,7 @@ def fetch_organization
   end
 
   def datasource_by_name
+    change_organization
     response = send_request('GET', format('%s/datasources/name/%s', resource[:grafana_api_path], ERB::Util.url_encode(resource[:name])))
     return nil if response.code == '404'
 
@@ -149,12 +150,15 @@ def secure_json_data
     {}
   end
 
+  def change_organization
+    response = send_request 'POST', format('%s/user/using/%s', resource[:grafana_api_path], fetch_organization[:id])
+    raise format('Failed to switch to org %s (HTTP response: %s/%s)', fetch_organization[:id], response.code, response.body) unless response.code == '200'
+  end
+
   def flush
     return if resource['ensure'] == :absent
 
-    # change organizations
-    response = send_request 'POST', format('%s/user/using/%s', resource[:grafana_api_path], fetch_organization[:id])
-    raise format('Failed to switch to org %s (HTTP response: %s/%s)', fetch_organization[:id], response.code, response.body) unless response.code == '200'
+    change_organization
 
     # Build the `data` to POST/PUT by first creating a hash with some defaults which will be used if we're _creating_ a datasource
     data = {
@@ -252,6 +256,11 @@ def destroy
   end
 
   def exists?
-    datasource
+    # check organization first. If it does not exist, then
+    # the datasource does not exist either. Furthermore this
+    # avoids the issue that a noop run does not actually create
+    # the organization, so that datasource(_by_name) cannot
+    # invoke change_organization().
+    fetch_organization and datasource
   end
 end

spec/acceptance/grafana_datasource_spec.rb

@@ -110,5 +110,38 @@ class { 'grafana':
         end
       end
     end
+
+    describe 'postgres ds' do
+      context 'without basic auth' do
+        let(:manifest) do
+          <<-PUPPET
+          ['Foo', 'Bar'].each |$organization| {
+              grafana_organization { $organization:
+                ensure           => present,
+                grafana_url      => 'http://localhost:3000',
+                grafana_user     => 'admin',
+                grafana_password => 'admin',
+              } ->
+              grafana_datasource { $organization:
+                organization     => $organization,
+                type             => 'grafana-postgresql-datasource',
+                url              => 'localhost',
+                grafana_url      => 'http://localhost:3000',
+                grafana_user     => 'admin',
+                grafana_password => 'admin',
+              }
+          }
+          PUPPET
+        end
+
+        it 'works with no errors' do
+          apply_manifest_on(default, manifest, catch_failures: true)
+        end
+
+        it 'is idempotent' do
+          apply_manifest_on(default, manifest, catch_changes: true)
+        end
+      end
+    end
   end
 end