[BUG] Gitlab 9.1 TypeError: Cannot read property 'base_sha' of

[iShawnWang]

Describe the bug

npm run danger:ci

> afl@1.0.1 danger:ci /Users/ishawnwang/ironman
> DANGER_GITLAB_API_BASE_URL=http://code.XXX.com/api/v4 DANGER_GITLAB_HOST=http://code.XXX.com/ DANGER_GITLAB_API_TOKEN=<TOKEN> danger pr http://code.XXX.com/lhs/ironman/merge_requests/1558

Starting Danger PR on lhs/ironman#1558
Error:  TypeError: Cannot read property 'base_sha' of
    at Object.exports.gitLabGitDSL (/Users/ishawnwang/ironman/node_modules/danger/distribution/platforms/gitlab/GitLabGit.js:45:38)
    at Object.<anonymous> (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:91:39)
    at step (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:32:23)
    at Object.next (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:13:53)
    at /Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:7:71
    at new Promise (<anonymous>)
    at __awaiter (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:3:12)
    at Object.exports.jsonToDSL (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:64:53)
    at Object.<anonymous> (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToContext.js:55:54)
    at step (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToContext.js:32:23)

TypeError: Cannot read property 'markdowns' of undefined
    at /Users/ishawnwang/ironman/node_modules/danger/distribution/commands/danger-runner.js:119:27
    at /Users/ishawnwang/ironman/node_modules/node-cleanup/node-cleanup.js:80:9
    at Array.forEach (<anonymous>)
    at process.exitHandler (/Users/ishawnwang/ironman/node_modules/node-cleanup/node-cleanup.js:79:21)
    at process.emit (events.js:315:20)

Error:  TypeError: Cannot read property 'base_sha' of undefined
    at Object.exports.gitLabGitDSL (/Users/ishawnwang/ironman/node_modules/danger/distribution/platforms/gitlab/GitLabGit.js:45:38)
    at Object.<anonymous> (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:91:39)
    at step (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:32:23)
    at Object.next (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:13:53)
    at /Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:7:71
    at new Promise (<anonymous>)
    at __awaiter (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:3:12)
    at Object.exports.jsonToDSL (/Users/ishawnwang/ironman/node_modules/danger/distribution/runner/jsonToDSL.js:64:53)
    at Object.<anonymous> (/Users/ishawnwang/ironman/node_modules/danger/distribution/commands/utils/runDangerSubprocess.js:162:54)
    at step (/Users/ishawnwang/ironman/node_modules/danger/distribution/commands/utils/runDangerSubprocess.js:43:23)
npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! afl@1.0.1 danger:ci: `DANGER_GITLAB_API_BASE_URL=http://code.XXX.com/api/v4 DANGER_GITLAB_HOST=http://code.XXX.com/ DANGER_GITLAB_API_TOKEN=<TOKEN> danger pr http://code.XXX.com/lhs/ironman/merge_requests/1558`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the afl@1.0.1 danger:ci script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/ishawnwang/.npm/_logs/2020-08-29T01_32_01_302Z-debug.log

To Reproduce
Steps to reproduce the behavior:

1. setup danger ci follow getting startted guide
2. npm run danger pr

Expected behavior

Screenshots
If applicable, add screenshots to help explain your problem.

** Your Environment**

software	version
danger.js	10.4.0
node	12.17.0
npm	6.14.7
Operating System	macos
gitlab	GitLab Community Edition 9.1.4 fed799a

Additional context

Found related issue #855 (comment) but still not work now

[iShawnWang]

After simple debugging, i found that there is no diff_refs.base_sha property in the response

console.log(JSON.stringify(gitlab.mr, null, 4))

{
    "id": 72212,
    "iid": 1558,
    "project_id": 2027,
    "title": "Feat/XXX",
    "description": "",
    "state": "merged",
    "created_at": "2020-08-27T13:01:36.871Z",
    "updated_at": "2020-08-27T13:01:39.850Z",
    "target_branch": "master",
    "source_branch": "feat/XXX",
    "upvotes": 0,
    "downvotes": 0,
    "author": {
        "name": "Shuai Wang",
        "username": "iShawnWang",
        "id": 451,
        "state": "active",
        "avatar_url": "http://code.XXX.com/uploads/user/avatar/451/avatar.png",
        "web_url": "http://code.XXX.com/iShawnWang"
    },
    "assignee": null,
    "source_project_id": 2027,
    "target_project_id": 2027,
    "labels": [],
    "work_in_progress": false,
    "milestone": null,
    "merge_when_pipeline_succeeds": false,
    "merge_status": "can_be_merged",
    "sha": "f8106c8f77623c594095c8ee3516138b5fb3d65f",
    "merge_commit_sha": "1a3ce1cf81717d21b348ca7119624ffaae91f688",
    "user_notes_count": 0,
    "should_remove_source_branch": null,
    "force_remove_source_branch": true,
    "web_url": "http://code.XXX.com/lhs/ironman/merge_requests/1558",
    "subscribed": true
}

[iShawnWang]

It working as expected now ~