What is the difference between unit.TypeXXXX.UnitGlobalDisabled() and .Permission.CanRead

[yp05327]

Feature Description

When I was reviewing the changes in my PR #22705,
I found something strange: why UnitPackagesGlobalDisabled here?
https://github.com/go-gitea/gitea/pull/22705/files#diff-8020089c79cc846f287e738cf57917d21ec16499df1d994e6c31309d06a1a5afL28

Then I searched UnitPackagesGlobalDisabled, it is not existed.
So what about UnitProjectsGlobalDisabled?
I found it in here.

gitea/modules/context/context.go

Line 783 in 7d3c4c3

ctx.Data["UnitProjectsGlobalDisabled"] = unit.TypeProjects.UnitGlobalDisabled()

The next question is why we didn't define UnitPackagesGlobalDisabled here. If it is not defined, how do we controll this unit's visibility in repo's header?
Then I checked the codes in repo's header:

gitea/templates/repo/header.tmpl

Lines 156 to 229 in b811ab4

	{{if .Permission.CanRead $.UnitTypeCode}}
	<a class="{{if .PageIsViewCode}}active {{end}}item" href="{{.RepoLink}}{{if (ne .BranchName .Repository.DefaultBranch)}}/src/{{.BranchNameSubURL}}{{end}}">
	{{svg "octicon-code"}} {{.locale.Tr "repo.code"}}
	</a>
	{{end}}
	{{if .Permission.CanRead $.UnitTypeIssues}}
	<a class="{{if .PageIsIssueList}}active {{end}}item" href="{{.RepoLink}}/issues">
	{{svg "octicon-issue-opened"}} {{.locale.Tr "repo.issues"}}
	{{if .Repository.NumOpenIssues}}
	<span class="ui small label">{{CountFmt .Repository.NumOpenIssues}}</span>
	{{end}}
	</a>
	{{end}}
	{{if .Permission.CanRead $.UnitTypeExternalTracker}}
	<a class="{{if .PageIsIssueList}}active {{end}}item" href="{{.RepoExternalIssuesLink}}" target="_blank" rel="noopener noreferrer">
	{{svg "octicon-link-external"}} {{.locale.Tr "repo.issues"}} </span>
	</a>
	{{end}}
	{{if and .Repository.CanEnablePulls (.Permission.CanRead $.UnitTypePullRequests)}}
	<a class="{{if .PageIsPullList}}active {{end}}item" href="{{.RepoLink}}/pulls">
	{{svg "octicon-git-pull-request"}} {{.locale.Tr "repo.pulls"}}
	{{if .Repository.NumOpenPulls}}
	<span class="ui small label">{{CountFmt .Repository.NumOpenPulls}}</span>
	{{end}}
	</a>
	{{end}}
	{{if and .EnableActions (not .UnitActionsGlobalDisabled) (.Permission.CanRead $.UnitTypeActions)}}
	<a class="{{if .PageIsActions}}active {{end}}item" href="{{.RepoLink}}/actions">
	{{svg "octicon-play"}} {{.locale.Tr "actions.actions"}}
	{{if .Repository.NumOpenActionRuns}}
	<span class="ui small label">{{CountFmt .Repository.NumOpenActionRuns}}</span>
	{{end}}
	</a>
	{{end}}
	{{if .Permission.CanRead $.UnitTypePackages}}
	<a href="{{.RepoLink}}/packages" class="{{if .IsPackagesPage}}active {{end}}item">
	{{svg "octicon-package"}} {{.locale.Tr "packages.title"}}
	</a>
	{{end}}
	{{if and (not .UnitProjectsGlobalDisabled) (.Permission.CanRead $.UnitTypeProjects)}}
	<a href="{{.RepoLink}}/projects" class="{{if .IsProjectsPage}}active {{end}}item">
	{{svg "octicon-project"}} {{.locale.Tr "repo.project_board"}}
	{{if .Repository.NumOpenProjects}}
	<span class="ui small label">{{CountFmt .Repository.NumOpenProjects}}</span>
	{{end}}
	</a>
	{{end}}
	{{if and (.Permission.CanRead $.UnitTypeReleases) (not .IsEmptyRepo)}}
	<a class="{{if .PageIsReleaseList}}active {{end}}item" href="{{.RepoLink}}/releases">
	{{svg "octicon-tag"}} {{.locale.Tr "repo.releases"}}
	{{if .NumReleases}}
	<span class="ui small label">{{CountFmt .NumReleases}}</span>
	{{end}}
	</a>
	{{end}}
	{{if or (.Permission.CanRead $.UnitTypeWiki) (.Permission.CanRead $.UnitTypeExternalWiki)}}
	<a class="{{if .PageIsWiki}}active {{end}}item" href="{{.RepoLink}}/wiki" {{if and (.Permission.CanRead $.UnitTypeExternalWiki) (not (HasPrefix ((.Repository.MustGetUnit $.Context $.UnitTypeExternalWiki).ExternalWikiConfig.ExternalWikiURL) (.Repository.Link)))}} target="_blank" rel="noopener noreferrer" {{end}}>
	{{svg "octicon-book"}} {{.locale.Tr "repo.wiki"}}
	</a>
	{{end}}
	{{if and (.Permission.CanReadAny $.UnitTypePullRequests $.UnitTypeIssues $.UnitTypeReleases) (not .IsEmptyRepo)}}
	<a class="{{if .PageIsActivity}}active {{end}}item" href="{{.RepoLink}}/activity">
	{{svg "octicon-pulse"}} {{.locale.Tr "repo.activity"}}
	</a>
	{{end}}

Almost of them use .Permission.CanRead to check the visibility, but some of them also use UnitXXXXXXGlobalDisabled. The definition is:

gitea/modules/context/context.go

Line 783 in b811ab4

ctx.Data["UnitProjectsGlobalDisabled"] = unit.TypeProjects.UnitGlobalDisabled()

---

And at someplaces, I found we also use settings.UnitName.Enabled
e.g.

gitea/modules/context/org.go

Line 159 in 3596df5

ctx.Data["IsPackageEnabled"] = setting.Packages.Enabled

It seems that UnitXXXXXXGlobalDisabled and the permission model is used for repo units,
and we have no permission model for user/org level packages/projects, so settings are used directly here.

---

Then the next question is what is the difference between them?
Im not familiar with go, and I don't understand how the permission model works now.
Maybe I asked a stupid question, but I want to make sure my PR's codes are correct.

---

Then I changed the app.ini, to disable Packages, it worked. It seems that .Permission.CanRead is correct.
Then I found DEFAULT_REPO_UNITS and DISABLED_REPO_UNITS in the document. It seems that we can control the repo unit by this setting option. I think maybe UnitXXXXXXGlobalDisabled is related to it?

Then I disabled Package and Projects, restart the server, but it didn't work, I can still access them.
Then I searched DISABLED_REPO_UNITS, and no record in any go files.
So I created this issue #23001
I made a mistake in setting the vaule of DISABLED_REPO_UNITS, but no warning or error info. Maybe we can add it. -> #23024

---

Screenshots

No response

[yp05327]

unit.TypeProjects.UnitGlobalDisabled() checks whether repo.projects is listed in DISABLED_REPO_UNITS
I removed UnitProjectsGlobalDisabled here, and it also worked with only .Permission.CanRead

gitea/templates/repo/header.tmpl

Line 201 in b811ab4

{{if and (not .UnitProjectsGlobalDisabled) (.Permission.CanRead $.UnitTypeProjects)}}

It seems that UnitXXXXXXDisabled (unit.TypeXXXXXX.UnitGlobalDisabled()) is not necessary, since we can use .Permission.CanRead.