[backports-release-1.10] allow extensions to trigger from packages in [deps] (JuliaLang#54009)

There is a use case where you have a weak dependency (for one of your
extensions) that is misbehaving and you quickly want to try debug that
issue. A workflow that feels reasonable for this could be:

```
pkg> dev WeakDependency

julia> using Package, WeakDependency

```

This doesn't work right now for two reasons:

1. Doing the `dev WeakDependency` will add the dependency to `[deps]`
but not remove it from `[weakdeps]` which means you all of a sudden are
in the scenario described in
https://pkgdocs.julialang.org/v1/creating-packages/#Transition-from-normal-dependency-to-extension
which is not what is desired.
2. The extension will not actually load because you can right now only
trigger extensions from weak deps getting loaded, not from deps getting
loaded.

Point 1. is fixed by JuliaLang/Pkg.jl#3865
Point 2. is fixed by this PR.

(cherry picked from commit f46cb4c)

Author: KristofferC

base/loading.jl

@@ -1211,12 +1211,13 @@ function insert_extension_triggers(env::String, pkg::PkgId)::Union{Nothing,Missi
         proj_pkg = project_file_name_uuid(project_file, pkg.name)
         if pkg == proj_pkg
             d_proj = parsed_toml(project_file)
-            weakdeps = get(d_proj, "weakdeps", nothing)::Union{Nothing, Vector{String}, Dict{String,Any}}
             extensions = get(d_proj, "extensions", nothing)::Union{Nothing, Dict{String, Any}}
             extensions === nothing && return
-            weakdeps === nothing && return
-            if weakdeps isa Dict{String, Any}
-                return _insert_extension_triggers(pkg, extensions, weakdeps)
+            weakdeps = get(Dict{String, Any}, d_proj, "weakdeps")::Union{Vector{String}, Dict{String,Any}}
+            deps = get(Dict{String, Any}, d_proj, "deps")::Union{Vector{String}, Dict{String,Any}}
+            if weakdeps isa Dict{String,Any} && deps isa Dict{String,Any}
+                total_deps = merge(weakdeps, deps)
+                return _insert_extension_triggers(pkg, extensions, total_deps)
             end
         end
 
@@ -1231,35 +1232,43 @@ function insert_extension_triggers(env::String, pkg::PkgId)::Union{Nothing,Missi
                 uuid = get(entry, "uuid", nothing)::Union{String, Nothing}
                 uuid === nothing && continue
                 if UUID(uuid) == pkg.uuid
-                    weakdeps = get(entry, "weakdeps", nothing)::Union{Nothing, Vector{String}, Dict{String,Any}}
                     extensions = get(entry, "extensions", nothing)::Union{Nothing, Dict{String, Any}}
                     extensions === nothing && return
-                    weakdeps === nothing && return
-                    if weakdeps isa Dict{String, Any}
-                        return _insert_extension_triggers(pkg, extensions, weakdeps)
+                    weakdeps = get(Dict{String, Any}, entry, "weakdeps")::Union{Vector{String}, Dict{String,Any}}
+                    deps = get(Dict{String, Any}, entry, "deps")::Union{Vector{String}, Dict{String,Any}}
+
+                    function expand_deps_list(deps′::Vector{String})
+                        deps′_expanded = Dict{String, Any}()
+                        for (dep_name, entries) in d
+                            dep_name in deps′ || continue
+                            entries::Vector{Any}
+                            if length(entries) != 1
+                                error("expected a single entry for $(repr(dep_name)) in $(repr(project_file))")
+                            end
+                            entry = first(entries)::Dict{String, Any}
+                            uuid = entry["uuid"]::String
+                            deps′_expanded[dep_name] = uuid
+                        end
+                        return deps′_expanded
                     end
 
-                    d_weakdeps = Dict{String, Any}()
-                    for (dep_name, entries) in d
-                        dep_name in weakdeps || continue
-                        entries::Vector{Any}
-                        if length(entries) != 1
-                            error("expected a single entry for $(repr(dep_name)) in $(repr(project_file))")
-                        end
-                        entry = first(entries)::Dict{String, Any}
-                        uuid = entry["uuid"]::String
-                        d_weakdeps[dep_name] = uuid
+                    if weakdeps isa Vector{String}
+                        weakdeps = expand_deps_list(weakdeps)
                     end
-                    @assert length(d_weakdeps) == length(weakdeps)
-                    return _insert_extension_triggers(pkg, extensions, d_weakdeps)
+                    if deps isa Vector{String}
+                        deps = expand_deps_list(deps)
+                    end
+
+                    total_deps = merge(weakdeps, deps)
+                    return _insert_extension_triggers(pkg, extensions, total_deps)
                 end
             end
         end
     end
     return nothing
 end
 
-function _insert_extension_triggers(parent::PkgId, extensions::Dict{String, Any}, weakdeps::Dict{String, Any})
+function _insert_extension_triggers(parent::PkgId, extensions::Dict{String, Any}, totaldeps::Dict{String, Any})
     for (ext, triggers) in extensions
         triggers = triggers::Union{String, Vector{String}}
         triggers isa String && (triggers = [triggers])
@@ -1273,7 +1282,7 @@ function _insert_extension_triggers(parent::PkgId, extensions::Dict{String, Any}
         push!(trigger1, gid)
         for trigger in triggers
             # TODO: Better error message if this lookup fails?
-            uuid_trigger = UUID(weakdeps[trigger]::String)
+            uuid_trigger = UUID(totaldeps[trigger]::String)
             trigger_id = PkgId(uuid_trigger, trigger)
             if !haskey(Base.loaded_modules, trigger_id) || haskey(package_locks, trigger_id)
                 trigger1 = get!(Vector{ExtensionId}, EXT_DORMITORY, trigger_id)