fix: allow ./test project merging

src/julia-1.11/activate_set.jl

@@ -40,7 +40,8 @@ function activate(pkg::AbstractString=current_pkg_name(); allow_reresolve=true)
             # Signature changed when workspaces were introduced to Pkg in v1.12 (see Pkg.jl#3841)
             subgraph = Pkg.Operations.prune_manifest(sandbox_manifest, VERSION < v"1.12.0-" ? [uuid] : Set([uuid]))
             for (uuid, entry) in subgraph
-                if haskey(working_manifest, uuid)
+                entry_working = get(working_manifest, uuid, nothing)
+                if entry_working !== nothing && entry_working != entry && (ctx.env.pkg !== nothing && ctx.env.pkg.uuid != uuid)
                     Pkg.Operations.pkgerror("can not merge projects")
                 end
                 working_manifest[uuid] = entry

src/julia-1.13/activate_set.jl

@@ -40,7 +40,8 @@ function activate(pkg::AbstractString=current_pkg_name(); allow_reresolve=true)
             # Signature changed when workspaces were introduced to Pkg in v1.12 (see Pkg.jl#3841)
             subgraph = Pkg.Operations.prune_manifest(sandbox_manifest, VERSION < v"1.12.0-" ? [uuid] : Set([uuid]))
             for (uuid, entry) in subgraph
-                if haskey(working_manifest, uuid)
+                entry_working = get(working_manifest, uuid, nothing)
+                if entry_working !== nothing && entry_working != entry && (ctx.env.pkg !== nothing && ctx.env.pkg.uuid != uuid)
                     Pkg.Operations.pkgerror("can not merge projects")
                 end
                 working_manifest[uuid] = entry

test/activate_set.jl

@@ -123,4 +123,24 @@
             end
         end
     end
+
+    if VERSION >= v"1.12-"
+        @testset "activate [workspace] test env" begin
+            orig_project_toml_path = Base.active_project()
+            push!(LOAD_PATH, mktempdir())  # put something weird in LOAD_PATH for testing
+            orig_load_path = Base.LOAD_PATH
+            try
+                Pkg.activate(joinpath(@__DIR__, "sources", "WorkspaceTestEnv"))
+                TestEnv.activate()
+                new_project_toml_path = Base.active_project()
+                @test new_project_toml_path != orig_project_toml_path
+                @test orig_load_path == Base.LOAD_PATH
+                @eval using WorkspaceTestEnv
+                @test isdefined(@__MODULE__, :WorkspaceTestEnv)
+                @test WorkspaceTestEnv.foo() == 42
+            finally
+                Pkg.activate(orig_project_toml_path)
+            end
+        end
+    end
 end

test/sources/WorkspaceTestEnv/Project.toml

@@ -0,0 +1,6 @@
+name = "WorkspaceTestEnv"
+uuid = "f7f074d6-898f-4820-8a1f-11e53eb7425f"
+version = "0.0.0"
+
+[workspace]
+projects = ["test"]

test/sources/WorkspaceTestEnv/src/WorkspaceTestEnv.jl

@@ -0,0 +1,5 @@
+module WorkspaceTestEnv
+
+foo() = 42
+
+end

test/sources/WorkspaceTestEnv/test/Project.toml

@@ -0,0 +1,3 @@
+[deps]
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+WorkspaceTestEnv = "f7f074d6-898f-4820-8a1f-11e53eb7425f"

test/sources/WorkspaceTestEnv/test/runtests.jl

@@ -0,0 +1,4 @@
+using WorkspaceTestEnv
+using Test
+
+@test WorkspaceTestEnv.foo() == 42