allow finding stdlibs that are normal packages in the manifest but are now stdlibs

base/loading.jl

@@ -463,6 +463,8 @@ function locate_package_env(pkg::PkgId, stopenv::Union{String, Nothing}=nothing)
             path = manifest_uuid_path(env, pkg)
             # missing is used as a sentinel to stop looking further down in envs
             if path === missing
+                # Before stopping, try stdlib fallback for missing stdlib dependencies
+                is_stdlib(pkg) && @goto stdlib_fallback
                 path = nothing
                 @goto done
             end
@@ -474,6 +476,7 @@ function locate_package_env(pkg::PkgId, stopenv::Union{String, Nothing}=nothing)
                 stopenv == env && break
             end
         end
+        @label stdlib_fallback
         # Allow loading of stdlibs if the name/uuid are given
         # e.g. if they have been explicitly added to the project/manifest
         mbypath = manifest_uuid_path(Sys.STDLIB, pkg)

test/loading.jl

@@ -1539,12 +1539,21 @@ end
     mktempdir() do depot
         # This manifest has a LibGit2 entry that is missing LibGit2_jll, which should be
         # handled by falling back to the stdlib Project.toml for dependency truth.
-        badmanifest_test_dir = joinpath(@__DIR__, "project", "deps", "BadStdlibDeps.jl")
+        badmanifest_test_dir = joinpath(@__DIR__, "project", "deps", "BadStdlibDeps")
         @test success(addenv(
             `$(Base.julia_cmd()) --project=$badmanifest_test_dir --startup-file=no -e 'using LibGit2'`,
             "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
         ))
     end
+    mktempdir() do depot
+        # This manifest has a LibGit2 entry that has a LibGit2_jll with a git-tree-hash1
+        # which simulates an old manifest where LibGit2_jll was not a stdlib
+        badmanifest_test_dir2 = joinpath(@__DIR__, "project", "deps", "BadStdlibDeps2")
+        @test success(addenv(
+            `$(Base.julia_cmd()) --project=$badmanifest_test_dir2 --startup-file=no -e 'using LibGit2'`,
+            "JULIA_DEPOT_PATH" => depot * Base.Filesystem.pathsep(),
+        ))
+    end
 end
 
 @testset "code coverage disabled during precompilation" begin

test/project/deps/BadStdlibDeps2/Manifest.toml

@@ -0,0 +1,54 @@
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.12.0-DEV"
+manifest_format = "2.0"
+project_hash = "dc9d33b0ee13d9466bdb75b8d375808a534a79ec"
+
+[[deps.Artifacts]]
+uuid = "56f22d72-fd6d-98f1-02f0-08ddc0907c33"
+version = "1.11.0"
+
+[[deps.LibGit2]]
+deps = ["NetworkOptions", "Printf", "SHA", "LibGit2_jll"]
+uuid = "76f85450-5226-5b5a-8eaa-529ad045b433"
+version = "1.11.0"
+
+# This is an stdlib but intentionally has a git-tree-sha1 because
+# we are emulating that the manifest comes from a version where
+# LibGit2_jll was not an stdlib
+[[deps.LibGit2_jll]]
+deps = ["Artifacts", "LibSSH2_jll", "Libdl", "MbedTLS_jll"]
+git-tree-sha1 = "1111111111111111111111111111111111111111"
+uuid = "e37daf67-58a4-590a-8e99-b0245dd2ffc5"
+version = "1.8.0+0"
+
+[[deps.LibSSH2_jll]]
+deps = ["Artifacts", "Libdl", "MbedTLS_jll"]
+uuid = "29816b5a-b9ab-546f-933c-edad1886dfa8"
+version = "1.11.0+1"
+
+[[deps.Libdl]]
+uuid = "8f399da3-3557-5675-b5ff-fb832c97cbdb"
+version = "1.11.0"
+
+[[deps.MbedTLS_jll]]
+deps = ["Artifacts", "Libdl"]
+uuid = "c8ffd9c3-330d-5841-b78e-0817d7145fa1"
+version = "2.28.6+1"
+
+[[deps.NetworkOptions]]
+uuid = "ca575930-c2e3-43a9-ace4-1e988b2c1908"
+version = "1.2.0"
+
+[[deps.Printf]]
+deps = ["Unicode"]
+uuid = "de0858da-6303-5e67-8744-51eddeeeb8d7"
+version = "1.11.0"
+
+[[deps.SHA]]
+uuid = "ea8e919c-243c-51af-8825-aaa63cd721ce"
+version = "0.7.0"
+
+[[deps.Unicode]]
+uuid = "4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5"
+version = "1.11.0"

test/project/deps/BadStdlibDeps2/Project.toml

@@ -0,0 +1,2 @@
+[deps]
+LibGit2 = "76f85450-5226-5b5a-8eaa-529ad045b433"