Replacing require.nil in api layer (#16906)

* Replacing require.nil in api layer

* Fixing some tests

* Fixing tests

* Addressing PR review comments

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

api4/post_test.go

@@ -199,7 +199,7 @@ func TestCreatePost(t *testing.T) {
 	CheckForbiddenStatus(t, resp)
 
 	r, err := Client.DoApiPost("/posts", "garbage")
-	require.Error(t, err)
+	require.NotNil(t, err)
 	require.Equal(t, http.StatusBadRequest, r.StatusCode)
 
 	Client.Logout()
@@ -230,7 +230,7 @@ func TestCreatePostEphemeral(t *testing.T) {
 	require.Equal(t, 0, int(rpost.EditAt), "newly created ephemeral post shouldn't have EditAt set")
 
 	r, err := Client.DoApiPost("/posts/ephemeral", "garbage")
-	require.Error(t, err)
+	require.NotNil(t, err)
 	require.Equal(t, http.StatusBadRequest, r.StatusCode)
 
 	Client.Logout()
@@ -664,20 +664,20 @@ func TestUpdatePost(t *testing.T) {
 
 	fileIds := make([]string, 3)
 	data, err := testutils.ReadTestFile("test.png")
-	require.Nil(t, err)
+	require.NoError(t, err)
 	for i := 0; i < len(fileIds); i++ {
 		fileResp, resp := Client.UploadFile(data, channel.Id, "test.png")
 		CheckNoError(t, resp)
 		fileIds[i] = fileResp.FileInfos[0].Id
 	}
 
-	rpost, err := th.App.CreatePost(&model.Post{
+	rpost, appErr := th.App.CreatePost(&model.Post{
 		UserId:    th.BasicUser.Id,
 		ChannelId: channel.Id,
 		Message:   "zz" + model.NewId() + "a",
 		FileIds:   fileIds,
 	}, channel, false, true)
-	require.Nil(t, err)
+	require.Nil(t, appErr)
 
 	assert.Equal(t, rpost.Message, rpost.Message, "full name didn't match")
 	assert.EqualValues(t, 0, rpost.EditAt, "Newly created post shouldn't have EditAt set")
@@ -744,12 +744,12 @@ func TestUpdatePost(t *testing.T) {
 		CheckBadRequestStatus(t, resp)
 	})
 
-	rpost3, err := th.App.CreatePost(&model.Post{
+	rpost3, appErr := th.App.CreatePost(&model.Post{
 		ChannelId: channel.Id,
 		Message:   "zz" + model.NewId() + "a",
 		UserId:    th.BasicUser.Id,
 	}, channel, false, true)
-	require.Nil(t, err)
+	require.Nil(t, appErr)
 
 	t.Run("new message, add files", func(t *testing.T) {
 		up3 := &model.Post{
@@ -847,7 +847,7 @@ func TestPatchPost(t *testing.T) {
 
 	fileIds := make([]string, 3)
 	data, err := testutils.ReadTestFile("test.png")
-	require.Nil(t, err)
+	require.NoError(t, err)
 	for i := 0; i < len(fileIds); i++ {
 		fileResp, resp := Client.UploadFile(data, channel.Id, "test.png")
 		CheckNoError(t, resp)
@@ -1721,7 +1721,7 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 
 	// Setting limit_after to zero should fail with a 400 BadRequest.
 	posts, resp := Client.GetPostsAroundLastUnread(userId, channelId, 20, 0, false)
-	require.Error(t, resp.Error)
+	require.NotNil(t, resp.Error)
 	require.Equal(t, "api.context.invalid_url_param.app_error", resp.Error.Id)
 	require.Equal(t, http.StatusBadRequest, resp.StatusCode)
 
@@ -1733,10 +1733,10 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 	// Set channel member's last viewed to 0.
 	// All returned posts are latest posts as if all previous posts were already read by the user.
 	channelMember, err := th.App.Srv().Store.Channel().GetMember(channelId, userId)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	channelMember.LastViewedAt = 0
 	_, err = th.App.Srv().Store.Channel().UpdateMember(channelMember)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	th.App.Srv().Store.Post().InvalidateLastPostTimeCache(channelId)
 
 	posts, resp = Client.GetPostsAroundLastUnread(userId, channelId, 20, 20, false)
@@ -1754,10 +1754,10 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 
 	// Set channel member's last viewed before post1.
 	channelMember, err = th.App.Srv().Store.Channel().GetMember(channelId, userId)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	channelMember.LastViewedAt = post1.CreateAt - 1
 	_, err = th.App.Srv().Store.Channel().UpdateMember(channelMember)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	th.App.Srv().Store.Post().InvalidateLastPostTimeCache(channelId)
 
 	posts, resp = Client.GetPostsAroundLastUnread(userId, channelId, 3, 3, false)
@@ -1778,10 +1778,10 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 
 	// Set channel member's last viewed before post6.
 	channelMember, err = th.App.Srv().Store.Channel().GetMember(channelId, userId)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	channelMember.LastViewedAt = post6.CreateAt - 1
 	_, err = th.App.Srv().Store.Channel().UpdateMember(channelMember)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	th.App.Srv().Store.Post().InvalidateLastPostTimeCache(channelId)
 
 	posts, resp = Client.GetPostsAroundLastUnread(userId, channelId, 3, 3, false)
@@ -1805,10 +1805,10 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 
 	// Set channel member's last viewed before post10.
 	channelMember, err = th.App.Srv().Store.Channel().GetMember(channelId, userId)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	channelMember.LastViewedAt = post10.CreateAt - 1
 	_, err = th.App.Srv().Store.Channel().UpdateMember(channelMember)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	th.App.Srv().Store.Post().InvalidateLastPostTimeCache(channelId)
 
 	posts, resp = Client.GetPostsAroundLastUnread(userId, channelId, 3, 3, false)
@@ -1830,10 +1830,10 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 
 	// Set channel member's last viewed equal to post10.
 	channelMember, err = th.App.Srv().Store.Channel().GetMember(channelId, userId)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	channelMember.LastViewedAt = post10.CreateAt
 	_, err = th.App.Srv().Store.Channel().UpdateMember(channelMember)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	th.App.Srv().Store.Post().InvalidateLastPostTimeCache(channelId)
 
 	posts, resp = Client.GetPostsAroundLastUnread(userId, channelId, 3, 3, false)
@@ -1870,10 +1870,10 @@ func TestGetPostsForChannelAroundLastUnread(t *testing.T) {
 	postIdNames[post13.Id] = "post13"
 
 	channelMember, err = th.App.Srv().Store.Channel().GetMember(channelId, userId)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	channelMember.LastViewedAt = post12.CreateAt - 1
 	_, err = th.App.Srv().Store.Channel().UpdateMember(channelMember)
-	require.Nil(t, err)
+	require.NoError(t, err)
 	th.App.Srv().Store.Post().InvalidateLastPostTimeCache(channelId)
 
 	posts, resp = Client.GetPostsAroundLastUnread(userId, channelId, 1, 2, false)