prevent loading other extensions when precompiling an extension (#55589)

The current way of loading extensions when precompiling an extension
very easily leads to cycles. For example, if you have more than one
extension and you happen to transitively depend on the triggers of one
of your extensions you will immediately hit a cycle where the extensions
will try to load each other indefinitely. This is an issue because you
cannot directly influence your transitive dependency graph so from this
p.o.v the current system of loading extension is "unsound".

The test added here checks this scenario and we can now precompile and
load it without any warnings or issues.

Would have made #55517 a non
issue.

Fixes #55557

---------

Co-authored-by: KristofferC <kristoffer.carlsson@juliacomputing.com>

Author: KristofferC

base/loading.jl

@@ -1387,7 +1387,9 @@ function run_module_init(mod::Module, i::Int=1)
 end
 
 function run_package_callbacks(modkey::PkgId)
-    run_extension_callbacks(modkey)
+    if !precompiling_extension
+        run_extension_callbacks(modkey)
+    end
     assert_havelock(require_lock)
     unlock(require_lock)
     try
@@ -2843,7 +2845,7 @@ end
 
 const PRECOMPILE_TRACE_COMPILE = Ref{String}()
 function create_expr_cache(pkg::PkgId, input::String, output::String, output_o::Union{Nothing, String},
-                           concrete_deps::typeof(_concrete_dependencies), flags::Cmd=``, internal_stderr::IO = stderr, internal_stdout::IO = stdout)
+                           concrete_deps::typeof(_concrete_dependencies), flags::Cmd=``, internal_stderr::IO = stderr, internal_stdout::IO = stdout, isext::Bool=false)
     @nospecialize internal_stderr internal_stdout
     rm(output, force=true)   # Remove file if it exists
     output_o === nothing || rm(output_o, force=true)
@@ -2912,7 +2914,7 @@ function create_expr_cache(pkg::PkgId, input::String, output::String, output_o::
     write(io.in, """
         empty!(Base.EXT_DORMITORY) # If we have a custom sysimage with `EXT_DORMITORY` prepopulated
         Base.track_nested_precomp($precomp_stack)
-        Base.precompiling_extension = $(loading_extension)
+        Base.precompiling_extension = $(loading_extension | isext)
         Base.precompiling_package = true
         Base.include_package_for_output($(pkg_str(pkg)), $(repr(abspath(input))), $(repr(depot_path)), $(repr(dl_load_path)),
             $(repr(load_path)), $deps, $(repr(source_path(nothing))))
@@ -2970,18 +2972,18 @@ This can be used to reduce package load times. Cache files are stored in
 `DEPOT_PATH[1]/compiled`. See [Module initialization and precompilation](@ref)
 for important notes.
 """
-function compilecache(pkg::PkgId, internal_stderr::IO = stderr, internal_stdout::IO = stdout; flags::Cmd=``, reasons::Union{Dict{String,Int},Nothing}=Dict{String,Int}())
+function compilecache(pkg::PkgId, internal_stderr::IO = stderr, internal_stdout::IO = stdout; flags::Cmd=``, reasons::Union{Dict{String,Int},Nothing}=Dict{String,Int}(), isext::Bool=false)
     @nospecialize internal_stderr internal_stdout
     path = locate_package(pkg)
     path === nothing && throw(ArgumentError("$(repr("text/plain", pkg)) not found during precompilation"))
-    return compilecache(pkg, path, internal_stderr, internal_stdout; flags, reasons)
+    return compilecache(pkg, path, internal_stderr, internal_stdout; flags, reasons, isext)
 end
 
 const MAX_NUM_PRECOMPILE_FILES = Ref(10)
 
 function compilecache(pkg::PkgId, path::String, internal_stderr::IO = stderr, internal_stdout::IO = stdout,
                       keep_loaded_modules::Bool = true; flags::Cmd=``, cacheflags::CacheFlags=CacheFlags(),
-                      reasons::Union{Dict{String,Int},Nothing}=Dict{String,Int}())
+                      reasons::Union{Dict{String,Int},Nothing}=Dict{String,Int}(), isext::Bool=false)
 
     @nospecialize internal_stderr internal_stdout
     # decide where to put the resulting cache file
@@ -3021,7 +3023,7 @@ function compilecache(pkg::PkgId, path::String, internal_stderr::IO = stderr, in
             close(tmpio_o)
             close(tmpio_so)
         end
-        p = create_expr_cache(pkg, path, tmppath, tmppath_o, concrete_deps, flags, internal_stderr, internal_stdout)
+        p = create_expr_cache(pkg, path, tmppath, tmppath_o, concrete_deps, flags, internal_stderr, internal_stdout, isext)
 
         if success(p)
             if cache_objects

base/precompilation.jl

@@ -435,51 +435,6 @@ function precompilepkgs(pkgs::Vector{String}=String[];
     # consider exts of direct deps to be direct deps so that errors are reported
     append!(direct_deps, keys(filter(d->last(d) in keys(env.project_deps), exts)))
 
-    # An extension effectively depends on another extension if it has all the the
-    # dependencies of that other extension
-    function expand_dependencies(depsmap)
-        function visit!(visited, node, all_deps)
-            if node in visited
-                return
-            end
-            push!(visited, node)
-            for dep in get(Set{Base.PkgId}, depsmap, node)
-                if !(dep in all_deps)
-                    push!(all_deps, dep)
-                    visit!(visited, dep, all_deps)
-                end
-            end
-        end
-
-        depsmap_transitive = Dict{Base.PkgId, Set{Base.PkgId}}()
-        for package in keys(depsmap)
-            # Initialize a set to keep track of all dependencies for 'package'
-            all_deps = Set{Base.PkgId}()
-            visited = Set{Base.PkgId}()
-            visit!(visited, package, all_deps)
-            # Update depsmap with the complete set of dependencies for 'package'
-            depsmap_transitive[package] = all_deps
-        end
-        return depsmap_transitive
-    end
-
-    depsmap_transitive = expand_dependencies(depsmap)
-
-    for (_, extensions_1) in pkg_exts_map
-        for extension_1 in extensions_1
-            deps_ext_1 = depsmap_transitive[extension_1]
-            for (_, extensions_2) in pkg_exts_map
-                for extension_2 in extensions_2
-                    extension_1 == extension_2 && continue
-                    deps_ext_2 = depsmap_transitive[extension_2]
-                    if issubset(deps_ext_2, deps_ext_1)
-                        push!(depsmap[extension_1], extension_2)
-                    end
-                end
-            end
-        end
-    end
-
     @debug "precompile: deps collected"
     # this loop must be run after the full depsmap has been populated
     for (pkg, pkg_exts) in pkg_exts_map
@@ -852,7 +807,7 @@ function precompilepkgs(pkgs::Vector{String}=String[];
                             t = @elapsed ret = precompile_pkgs_maybe_cachefile_lock(io, print_lock, fancyprint, pkg_config, pkgspidlocked, hascolor) do
                                 Base.with_logger(Base.NullLogger()) do
                                     # The false here means we ignore loaded modules, so precompile for a fresh session
-                                    Base.compilecache(pkg, sourcepath, std_pipe, std_pipe, false; flags, cacheflags)
+                                    Base.compilecache(pkg, sourcepath, std_pipe, std_pipe, false; flags, cacheflags, isext = haskey(exts, pkg))
                                 end
                             end
                             if ret isa Base.PrecompilableError

test/loading.jl

@@ -1155,6 +1155,19 @@ end
         finally
             copy!(LOAD_PATH, old_load_path)
         end
+
+        # Extension with cycles in dependencies
+        code = """
+        using CyclicExtensions
+        Base.get_extension(CyclicExtensions, :ExtA) isa Module || error("expected extension to load")
+        Base.get_extension(CyclicExtensions, :ExtB) isa Module || error("expected extension to load")
+        CyclicExtensions.greet()
+        """
+        proj = joinpath(@__DIR__, "project", "Extensions", "CyclicExtensions")
+        cmd =  `$(Base.julia_cmd()) --startup-file=no -e $code`
+        cmd = addenv(cmd, "JULIA_LOAD_PATH" => proj)
+        @test occursin("Hello Cycles!", String(read(cmd)))
+
     finally
         try
             rm(depot_path, force=true, recursive=true)

test/project/Extensions/CyclicExtensions/Manifest.toml

@@ -0,0 +1,21 @@
+# This file is machine-generated - editing it directly is not advised
+
+julia_version = "1.10.4"
+manifest_format = "2.0"
+project_hash = "ec25ff8df3a5e2212a173c3de2c7d716cc47cd36"
+
+[[deps.ExtDep]]
+deps = ["SomePackage"]
+path = "../ExtDep.jl"
+uuid = "fa069be4-f60b-4d4c-8b95-f8008775090c"
+version = "0.1.0"
+
+[[deps.ExtDep2]]
+path = "../ExtDep2"
+uuid = "55982ee5-2ad5-4c40-8cfe-5e9e1b01500d"
+version = "0.1.0"
+
+[[deps.SomePackage]]
+path = "../SomePackage"
+uuid = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+version = "0.1.0"

test/project/Extensions/CyclicExtensions/Project.toml

@@ -0,0 +1,13 @@
+name = "CyclicExtensions"
+uuid = "17d4f0df-b55c-4714-ac4b-55fa23f7355c"
+version = "0.1.0"
+
+[deps]
+ExtDep = "fa069be4-f60b-4d4c-8b95-f8008775090c"
+
+[weakdeps]
+SomePackage = "678608ae-7bb3-42c7-98b1-82102067a3d8"
+
+[extensions]
+ExtA = ["SomePackage"]
+ExtB = ["SomePackage"]

test/project/Extensions/CyclicExtensions/ext/ExtA.jl

@@ -0,0 +1,6 @@
+module ExtA
+
+using CyclicExtensions
+using SomePackage
+
+end

test/project/Extensions/CyclicExtensions/ext/ExtB.jl

@@ -0,0 +1,6 @@
+module ExtB
+
+using CyclicExtensions
+using SomePackage
+
+end

test/project/Extensions/CyclicExtensions/src/CyclicExtensions.jl

@@ -0,0 +1,7 @@
+module CyclicExtensions
+
+using ExtDep
+
+greet() = print("Hello Cycles!")
+
+end # module CyclicExtensions