automatic recompilation of stale cache files (fixes JuliaLang#12259)

Author: stevengj

base/loading.jl

@@ -58,9 +58,10 @@ function _include_from_serialized(content::Vector{UInt8})
 end
 
 # returns an array of modules loaded, or nothing if failed
-function _require_from_serialized(node::Int, path_to_try::ByteString, toplevel_load::Bool)
+function _require_from_serialized(node::Int, mod::Symbol, path_to_try::ByteString, toplevel_load::Bool)
     restored = nothing
     if toplevel_load && myid() == 1 && nprocs() > 1
+        recompile_stale(mod, path_to_try)
         # broadcast top-level import/using from node 1 (only)
         if node == myid()
             content = open(readbytes, path_to_try)
@@ -78,6 +79,7 @@ function _require_from_serialized(node::Int, path_to_try::ByteString, toplevel_l
             end
         end
     elseif node == myid()
+        myid() == 1 && recompile_stale(mod, path_to_try)
         restored = ccall(:jl_restore_incremental, Any, (Ptr{Uint8},), path_to_try)
     else
         content = remotecall_fetch(node, open, readbytes, path_to_try)
@@ -89,8 +91,9 @@ end
 
 function _require_from_serialized(node::Int, mod::Symbol, toplevel_load::Bool)
     paths = @fetchfrom node find_all_in_cache_path(mod)
+    sort!(paths, by=mtime, rev=true) # try newest cachefiles first
     for path_to_try in paths
-        restored = _require_from_serialized(node, path_to_try, toplevel_load)
+        restored = _require_from_serialized(node, mod, path_to_try, toplevel_load)
         if restored === nothing
             warn("deserialization checks failed while attempting to load cache from $path_to_try")
         else
@@ -152,7 +155,7 @@ function require(mod::Symbol)
         if JLOptions().incremental != 0
             # spawn off a new incremental compile task from node 1 for recursive `require` calls
             cachefile = compile(mod)
-            if nothing === _require_from_serialized(1, cachefile, last)
+            if nothing === _require_from_serialized(1, mod, cachefile, last)
                 warn("require failed to create a precompiled cache file")
             end
             return
@@ -315,3 +318,30 @@ function cache_dependencies(cachefile::AbstractString)
     end
     return modules, files
 end
+
+function stale_cachefile(cachefile::AbstractString, cachefile_mtime::Real=mtime(cachefile))
+    modules, files = cache_dependencies(cachefile)
+    for f in files
+        if mtime(f) > cachefile_mtime
+            return true
+        end
+    end
+    # files are not stale, so module list is valid and needs checking
+    for (M,uuid) in modules
+        if !isdefined(Main, M)
+            require(M) # should recursively recompile module M if stale
+        end
+        if module_uuid(Main.(M)) != uuid
+            return true
+        end
+    end
+    return false # fresh cachefile
+end
+
+function recompile_stale(mod, cachefile)
+    cachestat = stat(cachefile)
+    if iswritable(cachestat) && stale_cachefile(cachefile, cachestat.mtime)
+        info("Recompiling stale cache file $cachefile for module $mod.")
+        create_expr_cache(find_in_path(string(mod)), cachefile)
+    end
+end