Load module on remote workers from master (v2)

base/loading.jl

@@ -218,8 +218,14 @@ function _require_search_from_serialized(node::Int, mod::Symbol, sourcepath::Str
     end
 
     for path_to_try in paths::Vector{String}
-        if stale_cachefile(sourcepath, path_to_try)
-            continue
+        if node == myid()
+            if stale_cachefile(sourcepath, path_to_try)
+                continue
+            end
+        else
+            if @fetchfrom node stale_cachefile(sourcepath, path_to_try)
+                continue
+            end
         end
         restored = _require_from_serialized(node, mod, path_to_try, toplevel_load)
         if isa(restored, Exception)

test/compile.jl

@@ -524,4 +524,55 @@ let module_name = string("a",randstring())
     rm(file_name)
 end
 
+# Issue #19960
+let
+    # ideally this would test with workers on a remote host that does not have access to the master node filesystem for loading
+    # can simulate this for local workers by using relative load paths on master node that are not valid on workers
+    # so addprocs before changing directory to temp directory, otherwise workers will inherit temp working directory
+
+    test_workers = addprocs(1)
+    temp_path = mktempdir()
+    save_cwd = pwd()
+    cd(temp_path)
+    load_path = mktempdir(temp_path)
+    load_cache_path = mktempdir(temp_path)
+    unshift!(LOAD_PATH, basename(load_path))
+    unshift!(Base.LOAD_CACHE_PATH, basename(load_cache_path))
+
+    ModuleA = :Issue19960A
+    ModuleB = :Issue19960B
+
+    write(joinpath(load_path, "$ModuleA.jl"),
+        """
+        __precompile__(true)
+        module $ModuleA
+            export f
+            f() = myid()
+        end
+        """)
+
+    write(joinpath(load_path, "$ModuleB.jl"),
+        """
+        __precompile__(true)
+        module $ModuleB
+            using $ModuleA
+            export g
+            g() = f()
+        end
+        """)
+
+    try
+        @eval using $ModuleB
+        for wid in test_workers
+            @test remotecall_fetch(g, wid) == wid
+        end
+    finally
+        shift!(LOAD_PATH)
+        shift!(Base.LOAD_CACHE_PATH)
+        cd(save_cwd)
+        rm(temp_path, recursive=true)
+        rmprocs(test_workers)
+    end
+end
+
 end # !withenv