Migrations: Compare backend and frontend outputs to ensure feature parity (#106851)

* wip: trying to understand how to get the ds info from migrator

* add datasource info provider

* Use DS service to fetch DS data

* add more tests cases to match with migrator cases

* Add snapshots

* Non-existing DS

* Add different DS for snapshots

* fix import

* Fix tests: guard against double initialization

* don't use full datasource package in test

* min version should be 35

* fix test

* fix conversion test

* Dashboards: Support schemaVersion v35 migration in backend

* Dashboards: Support schemaVersion v34 migration in backend

* Dashboards: Support schemaVersion v33 migration in backend

* Apply suggestions from code review

Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

* Apply feedback

* Remove unused parameters

* Refactor to follow Go patterns

* Update logic

* Only write final migration result as output

* Compare backend and frontend results

* Improve snapshots to cover all possible use cases

* Linter

* wip make it consistent v33

* apply feedback

* Return default when the ref cannot be found

* Update apps/dashboard/pkg/migration/schemaversion/v33.go

Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

* apply feedback

* Use same mocks backend/frontend

* restore migrations

* update snapshots

* Adapt migration tests to use min versions

* Ensure v40-v41 works

* Ensure v39-v40 works

* Simplify the naming of the files

* adjust jest to new input convention

* Ensure every migration v36-v41 works

* Improve v38 naming

* Ensure v36 migrates correctly

* Skip v36 refs migrations on rows

* Treat rows as frontend and ensure same results for v36

* Ensure v34 runs with the same logic than the frontend

* Leave empty stadistics as valid option

* ensure v33 is working as the frontend

* Update tests

* Undo frontend changes for legend handling

* Remove filtering by version in the frontend

* linter

* Clean up v33 input JSON

---------

Co-authored-by: Todd Treece <360020+toddtreece@users.noreply.github.com>
Co-authored-by: Haris Rozajac <haris.rozajac12@gmail.com>
Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

apps/dashboard/pkg/migration/testutil/mocks.go

@@ -8,19 +8,51 @@ func (m *TestDataSourceProvider) GetDataSourceInfo() []schemaversion.DataSourceI
 	return []schemaversion.DataSourceInfo{
 		{
 			Default:    true,
-			UID:        "default-ds",
+			UID:        "default-ds-uid",
 			Type:       "prometheus",
 			APIVersion: "v1",
-			Name:       "Default",
+			Name:       "Default Test Datasource Name",
 			ID:         1,
 		},
 		{
 			Default:    false,
-			UID:        "other-ds",
+			UID:        "non-default-test-ds-uid",
+			Type:       "loki",
+			APIVersion: "1",
+			Name:       "Non Default Test Datasource Name",
+			ID:         2,
+		},
+		{
+			Default:    false,
+			UID:        "existing-ref-uid",
+			Type:       "prometheus",
+			APIVersion: "v1",
+			Name:       "Existing Ref Name",
+			ID:         3,
+		},
+		{
+			Default:    false,
+			UID:        "existing-target-uid",
 			Type:       "elasticsearch",
 			APIVersion: "v2",
-			Name:       "Elasticsearch",
-			ID:         2,
+			Name:       "Existing Target Name",
+			ID:         4,
+		},
+		{
+			Default:    false,
+			UID:        "existing-ref",
+			Type:       "prometheus",
+			APIVersion: "v1",
+			Name:       "Existing Ref Name",
+			ID:         5,
+		},
+		{
+			Default:    false,
+			UID:        "-- Mixed --",
+			Type:       "mixed",
+			APIVersion: "v1",
+			Name:       "-- Mixed --",
+			ID:         6,
 		},
 	}
 }