minimal hook into loading needed for Pkg3 (take 2)

base/REPLCompletions.jl

@@ -494,7 +494,7 @@ function completions(string, pos)
         s = string[startpos:pos]
         if dotpos <= startpos
             for dir in [Pkg.dir(); LOAD_PATH; pwd()]
-                isdir(dir) || continue
+                dir isa AbstractString && isdir(dir) || continue
                 for pname in readdir(dir)
                     if pname[1] != '.' && pname != "METADATA" &&
                         pname != "REQUIRE" && startswith(pname, s)

base/initdefs.jl

@@ -30,11 +30,23 @@ isinteractive() = (is_interactive::Bool)
 """
     LOAD_PATH
 
-An array of paths (as strings) where the `require` function looks for code.
+An array of paths as strings or custom loader objects for the `require`
+function and `using` and `import` statements to consider when loading
+code. To create a custom loader type, define the type and then add
+appropriate methods to the `Base.load_hook` function with the following
+signature:
+
+    Base.load_hook(loader::Loader, name::String, found::Any)
+
+The `loader` argument is the current value in `LOAD_PATH`, `name` is the
+name of the module to load, and `found` is the path of any previously
+found code to provide `name`. If no provider has been found earlier in
+`LOAD_PATH` then the value of `found` will be `nothing`. Custom loader
+functionality is experimental and may break or change in Julia 1.0.
 """
-const LOAD_PATH = String[]
-
+const LOAD_PATH = Any[]
 const LOAD_CACHE_PATH = String[]
+
 function init_load_path()
     vers = "v$(VERSION.major).$(VERSION.minor)"
     if haskey(ENV, "JULIA_LOAD_PATH")

base/loading.jl

@@ -80,19 +80,26 @@ else
     end
 end
 
-function try_path(prefix::String, base::String, name::String)
-    path = joinpath(prefix, name)
+function load_hook(prefix::String, name::String, ::Void)
+    name_jl = "$name.jl"
+    path = joinpath(prefix, name_jl)
     isfile_casesensitive(path) && return abspath(path)
-    path = joinpath(prefix, base, "src", name)
+    path = joinpath(prefix, name_jl, "src", name_jl)
     isfile_casesensitive(path) && return abspath(path)
-    path = joinpath(prefix, name, "src", name)
+    path = joinpath(prefix, name, "src", name_jl)
     isfile_casesensitive(path) && return abspath(path)
     return nothing
 end
+load_hook(prefix::String, name::String, path::String) = path
+load_hook(prefix, name::String, ::Any) =
+    throw(ArgumentError("unrecognized custom loader in LOAD_PATH: $prefix"))
+
+_str(x::AbstractString) = String(x)
+_str(x) = x
 
 # `wd` is a working directory to search. defaults to current working directory.
 # if `wd === nothing`, no extra path is searched.
-function find_in_path(name::String, wd)
+function find_in_path(name::String, wd::Union{Void,String})
     isabspath(name) && return name
     base = name
     if endswith(name,".jl")
@@ -103,15 +110,15 @@ function find_in_path(name::String, wd)
     if wd !== nothing
         isfile_casesensitive(joinpath(wd,name)) && return joinpath(wd,name)
     end
-    p = try_path(Pkg.dir(), base, name)
-    p !== nothing && return p
-    for prefix in LOAD_PATH
-        p = try_path(prefix, base, name)
-        p !== nothing && return p
+    path = nothing
+    path = _str(load_hook(_str(Pkg.dir()), base, path))
+    for dir in LOAD_PATH
+        path = _str(load_hook(_str(dir), base, path))
     end
-    return nothing
+    return path
 end
-find_in_path(name::AbstractString, wd = pwd()) = find_in_path(String(name), wd)
+find_in_path(name::AbstractString, wd::AbstractString = pwd()) =
+    find_in_path(String(name), String(wd))
 
 function find_in_node_path(name::String, srcpath, node::Int=1)
     if myid() == node

base/pkg/entry.jl

@@ -600,9 +600,11 @@ function build!(pkgs::Vector, errs::Dict, seen::Set=Set())
     # are serialized to errfile for later retrieval into errs[pkg]
     errfile = tempname()
     close(open(errfile, "w")) # create empty file
+    # TODO: serialize the same way the load cache does, not with strings
+    LOAD_PATH = filter(x -> x isa AbstractString, Base.LOAD_PATH)
     code = """
         empty!(Base.LOAD_PATH)
-        append!(Base.LOAD_PATH, $(repr(Base.LOAD_PATH)))
+        append!(Base.LOAD_PATH, $(repr(LOAD_PATH)))
         empty!(Base.LOAD_CACHE_PATH)
         append!(Base.LOAD_CACHE_PATH, $(repr(Base.LOAD_CACHE_PATH)))
         empty!(Base.DL_LOAD_PATH)

test/loading.jl

@@ -40,7 +40,29 @@ mktempdir() do dir
     end
 end
 
-let paddedname = "Ztest_sourcepath.jl"
-    filename = SubString(paddedname, 2, length(paddedname))
-    @test Base.find_in_path(filename) == abspath(paddedname[2:end])
+SAVED_LOAD_PATH = copy(LOAD_PATH)
+empty!(LOAD_PATH)
+dir = abspath(@__DIR__)
+push!(LOAD_PATH, dir)
+
+@test Base.find_in_path("test_sourcepath") == joinpath(dir, "test_sourcepath.jl")
+@test Base.find_in_path(GenericString("test_sourcepath")) == joinpath(dir, "test_sourcepath.jl")
+LOAD_PATH[end] = GenericString(LOAD_PATH[end])
+@test Base.find_in_path("test_sourcepath") == joinpath(dir, "test_sourcepath.jl")
+
+immutable CustomLoader
+    path::String
 end
+push!(LOAD_PATH, CustomLoader("abc"))
+let name = randstring(20)
+    @test_throws ArgumentError Base.find_in_path(name, nothing)
+    Base.load_hook(prefix::CustomLoader, name::String, found) = joinpath(prefix.path, name)
+    @test Base.find_in_path(name, nothing) == joinpath("abc", name)
+end
+@test Base.find_in_path("test_sourcepath", nothing) == joinpath("abc", "test_sourcepath")
+Base.load_hook(prefix::CustomLoader, name::String, found::String) = found
+@test Base.find_in_path("test_sourcepath", nothing) == joinpath(dir, "test_sourcepath.jl")
+
+empty!(LOAD_PATH)
+append!(LOAD_PATH, SAVED_LOAD_PATH)
+@test LOAD_PATH == SAVED_LOAD_PATH