LocalBackend named appc.AppConnector in its appConnector field, in the
field's constructor call, and in the AppConnector accessor, so even
builds with ts_omit_appconnectors linked the appc package and its
dependencies. The buildfeatures.HasAppConnectors checks let the linker
drop the code but could not remove the import.
Add a build-tag-gated type for the field: appcAppConnector is an alias
for appc.AppConnector by default, and in ts_omit_appconnectors builds it
is an empty struct with no-op versions of the methods local.go calls, so
the shared code still type checks. The constructor call moves behind a
newAppConnector helper in the same gated file, and the AppConnector
accessor keeps its *appc.AppConnector signature there, with a nil-
returning version in the omitted build.
This takes tailscale.com/appc out of depaware-min.txt and
depaware-minbox.txt. Add a DepChecker test to keep it out; it also sets
ts_omit_conn25, since conn25 uses appc as well.
Updates #12614
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: Ia7e2d9c4f1b8e6a3d5c0f2b7e9a1c4d6f8b0e2a5
Brad Fitzpatrick
2a61a720e5