[cocoon] Migrate flaky issue bot to null safety #90139
Description
Related to flutter/cocoon#1246
For various reasons, these tests directly call postJSON which is a generic function. This requires a fallback generator to support (which was done for github webhooks). However, the code here is calling it in a way that does generate the same function signature with what flaky tests is expecting.
Check flaky Can file issue and pr for framework host-only test [E]
MissingStubError: 'postJSON'
No stub was found which matches the arguments of this method call:
postJSON('/repos/flutter/flutter/pulls/123/requested_reviewers', {statusCode: null, fail: null, headers: null, params: null, convert: Closure: (Map<String, dynamic>) => PullRequest, body: {"reviewers":["HansMuller"]}, preview: null})
Add a stub for this method using Mockito's 'when' API, or generate the mock for MockGitHub with 'returnNullOnMissingStub: true'.
package:mockito/src/mock.dart 190:7 Mock._noSuchMethod
package:mockito/src/mock.dart 184:45 Mock.noSuchMethod
test/src/utilities/mocks.mocks.dart 2272:14 MockGitHub.postJSON
package:cocoon_service/src/service/github_service.dart 139:18 GithubService.assignReviewer
package:cocoon_service/src/request_handlers/file_flaky_issue_and_pr.dart 115:18 FileFlakyIssueAndPR._fileIssueAndPR
===== asynchronous gap ===========================
package:cocoon_service/src/request_handlers/file_flaky_issue_and_pr.dart 49:7 FileFlakyIssueAndPR.get
===== asynchronous gap ===========================
test/request_handlers/file_flaky_issue_and_pr_test.dart 232:18 main.<fn>.<fn>