Add CompilePreferences standard library

This commit adds the `CompilePreferences` standard library; a way to store a
TOML-serializable dictionary into top-level `Project.toml` files, then
force recompilation of child projects when the preferences are modified.

This commid adds the `CompilePreferences` standard library, which does
the actual writing to `Project.toml` files, as well as modifies the
loading code to check whether the preferences have changed.

Author: staticfloat

NEWS.md

@@ -111,6 +111,8 @@ Standard library changes
 * The `Pkg.Artifacts` module has been imported as a separate standard library.  It is still available as
   `Pkg.Artifacts`, however starting from Julia v1.6+, packages may import simply `Artifacts` without importing
   all of `Pkg` alongside. ([#37320])
+* A new standard library, `CompilePreferences`, has been added to allow packages to store settings within the top-
+  level `Project.toml`, and force recompilation when the preferences are changed. ([#xxxxx])
 
 #### LinearAlgebra
 

base/loading.jl

@@ -943,7 +943,7 @@ function _require(pkg::PkgId, cache::TOMLCache)
             if (0 == ccall(:jl_generating_output, Cint, ())) || (JLOptions().incremental != 0)
                 # spawn off a new incremental pre-compile task for recursive `require` calls
                 # or if the require search declared it was pre-compiled before (and therefore is expected to still be pre-compilable)
-                cachefile = compilecache(pkg, path)
+                cachefile = compilecache(pkg, path, cache)
                 if isa(cachefile, Exception)
                     if precompilableerror(cachefile)
                         verbosity = isinteractive() ? CoreLogging.Info : CoreLogging.Debug
@@ -1183,7 +1183,7 @@ end
 @assert precompile(create_expr_cache, (String, String, typeof(_concrete_dependencies), Nothing))
 @assert precompile(create_expr_cache, (String, String, typeof(_concrete_dependencies), UUID))
 
-function compilecache_path(pkg::PkgId)::String
+function compilecache_path(pkg::PkgId, cache::TOMLCache)::String
     entrypath, entryfile = cache_file_entry(pkg)
     cachepath = joinpath(DEPOT_PATH[1], entrypath)
     isdir(cachepath) || mkpath(cachepath)
@@ -1193,6 +1193,7 @@ function compilecache_path(pkg::PkgId)::String
         crc = _crc32c(something(Base.active_project(), ""))
         crc = _crc32c(unsafe_string(JLOptions().image_file), crc)
         crc = _crc32c(unsafe_string(JLOptions().julia_bin), crc)
+        crc = _crc32c(get_preferences_hash(pkg.uuid, cache), crc)
         project_precompile_slug = slug(crc, 5)
         abspath(cachepath, string(entryfile, "_", project_precompile_slug, ".ji"))
     end
@@ -1209,14 +1210,14 @@ for important notes.
 function compilecache(pkg::PkgId, cache::TOMLCache = TOMLCache())
     path = locate_package(pkg, cache)
     path === nothing && throw(ArgumentError("$pkg not found during precompilation"))
-    return compilecache(pkg, path)
+    return compilecache(pkg, path, cache)
 end
 
 const MAX_NUM_PRECOMPILE_FILES = 10
 
-function compilecache(pkg::PkgId, path::String)
+function compilecache(pkg::PkgId, path::String, cache::TOMLCache = TOMLCache())
     # decide where to put the resulting cache file
-    cachefile = compilecache_path(pkg)
+    cachefile = compilecache_path(pkg, cache)
     cachepath = dirname(cachefile)
     # prune the directory with cache files
     if pkg.uuid !== nothing
@@ -1320,6 +1321,8 @@ function parse_cache_header(f::IO)
         end
         totbytes -= 4 + 4 + n2 + 8
     end
+    prefs_hash = read(f, UInt64)
+    totbytes -= 8
     @assert totbytes == 12 "header of cache file appears to be corrupt"
     srctextpos = read(f, Int64)
     # read the list of modules that are required to be present during loading
@@ -1332,7 +1335,7 @@ function parse_cache_header(f::IO)
         build_id = read(f, UInt64) # build id
         push!(required_modules, PkgId(uuid, sym) => build_id)
     end
-    return modules, (includes, requires), required_modules, srctextpos
+    return modules, (includes, requires), required_modules, srctextpos, prefs_hash
 end
 
 function parse_cache_header(cachefile::String; srcfiles_only::Bool=false)
@@ -1341,21 +1344,21 @@ function parse_cache_header(cachefile::String; srcfiles_only::Bool=false)
         !isvalid_cache_header(io) && throw(ArgumentError("Invalid header in cache file $cachefile."))
         ret = parse_cache_header(io)
         srcfiles_only || return ret
-        modules, (includes, requires), required_modules, srctextpos = ret
+        modules, (includes, requires), required_modules, srctextpos, prefs_hash = ret
         srcfiles = srctext_files(io, srctextpos)
         delidx = Int[]
         for (i, chi) in enumerate(includes)
             chi.filename ∈ srcfiles || push!(delidx, i)
         end
         deleteat!(includes, delidx)
-        return modules, (includes, requires), required_modules, srctextpos
+        return modules, (includes, requires), required_modules, srctextpos, prefs_hash
     finally
         close(io)
     end
 end
 
 function cache_dependencies(f::IO)
-    defs, (includes, requires), modules = parse_cache_header(f)
+    defs, (includes, requires), modules, srctextpos, prefs_hash = parse_cache_header(f)
     return modules, map(chi -> (chi.filename, chi.mtime), includes)  # return just filename and mtime
 end
 
@@ -1370,7 +1373,7 @@ function cache_dependencies(cachefile::String)
 end
 
 function read_dependency_src(io::IO, filename::AbstractString)
-    modules, (includes, requires), required_modules, srctextpos = parse_cache_header(io)
+    modules, (includes, requires), required_modules, srctextpos, prefs_hash = parse_cache_header(io)
     srctextpos == 0 && error("no source-text stored in cache file")
     seek(io, srctextpos)
     return _read_dependency_src(io, filename)
@@ -1415,6 +1418,20 @@ function srctext_files(f::IO, srctextpos::Int64)
     return files
 end
 
+function get_preferences_hash(uuid::UUID, cache::TOMLCache = TOMLCache())
+    # check that project preferences match by first loading the Project.toml
+    active_project_file = Base.active_project()
+    if isfile(active_project_file)
+        preferences = get(parsed_toml(cache, active_project_file), "preferences", Dict{String,Any}())
+        if haskey(preferences, string(uuid))
+            return UInt64(hash(preferences[string(uuid)]))
+        end
+    end
+    return UInt64(hash(Dict{String,Any}()))
+end
+get_preferences_hash(::Nothing, cache::TOMLCache = TOMLCache()) = UInt64(hash(Dict{String,Any}()))
+get_preferences_hash(m::Module, cache::TOMLCache = TOMLCache()) = get_preferences_hash(PkgId(m).uuid, cache)
+
 # returns true if it "cachefile.ji" is stale relative to "modpath.jl"
 # otherwise returns the list of dependencies to also check
 stale_cachefile(modpath::String, cachefile::String) = stale_cachefile(modpath, cachefile, TOMLCache())
@@ -1425,7 +1442,7 @@ function stale_cachefile(modpath::String, cachefile::String, cache::TOMLCache)
             @debug "Rejecting cache file $cachefile due to it containing an invalid cache header"
             return true # invalid cache file
         end
-        (modules, (includes, requires), required_modules) = parse_cache_header(io)
+        modules, (includes, requires), required_modules, srctextpos, prefs_hash = parse_cache_header(io)
         id = isempty(modules) ? nothing : first(modules).first
         modules = Dict{PkgId, UInt64}(modules)
 
@@ -1500,6 +1517,12 @@ function stale_cachefile(modpath::String, cachefile::String, cache::TOMLCache)
         end
 
         if isa(id, PkgId)
+            curr_prefs_hash = get_preferences_hash(id.uuid, cache)
+            if prefs_hash != curr_prefs_hash
+                @debug "Rejecting cache file $cachefile because preferences hash does not match 0x$(string(prefs_hash, base=16)) != 0x$(string(curr_prefs_hash, base=16))"
+                return true
+            end
+
             get!(PkgOrigin, pkgorigins, id).cachepath = cachefile
         end
 

base/sysimg.jl

@@ -47,6 +47,7 @@ let
             :Distributed,
             :SharedArrays,
             :TOML,
+            :CompilePreferences,
             :Artifacts,
             :Pkg,
             :Test,

base/util.jl

@@ -385,6 +385,8 @@ _crc32c(io::IO, crc::UInt32=0x00000000) = _crc32c(io, typemax(Int64), crc)
 _crc32c(io::IOStream, crc::UInt32=0x00000000) = _crc32c(io, filesize(io)-position(io), crc)
 _crc32c(uuid::UUID, crc::UInt32=0x00000000) =
     ccall(:jl_crc32c, UInt32, (UInt32, Ref{UInt128}, Csize_t), crc, uuid.value, 16)
+_crc32c(x::Integer, crc::UInt32=0x00000000) =
+    ccall(:jl_crc32c, UInt32, (UInt32, Vector{UInt8}, Csize_t), crc, reinterpret(UInt8, [x]), sizeof(x))
 
 """
     @kwdef typedef

src/dump.c

@@ -1123,6 +1123,31 @@ static int64_t write_dependency_list(ios_t *s, jl_array_t **udepsp, jl_array_t *
             write_int32(s, 0);
         }
         write_int32(s, 0); // terminator, for ease of reading
+
+        // Calculate CompilePreferences hash for current package.
+        jl_value_t *prefs_hash = NULL;
+        if (jl_base_module) {
+            // Toplevel module is the module we're currently compiling, use it to get our preferences hash
+            jl_value_t * toplevel = (jl_value_t*)jl_get_global(jl_base_module, jl_symbol("__toplevel__"));
+            jl_value_t * prefs_hash_func = jl_get_global(jl_base_module, jl_symbol("get_preferences_hash"));
+
+            if (toplevel && prefs_hash_func) {
+                // call get_preferences_hash(__toplevel__)
+                jl_value_t *prefs_hash_args[2] = {prefs_hash_func, (jl_value_t*)toplevel};
+                size_t last_age = jl_get_ptls_states()->world_age;
+                jl_get_ptls_states()->world_age = jl_world_counter;
+                prefs_hash = (jl_value_t*)jl_apply(prefs_hash_args, 2);
+                jl_get_ptls_states()->world_age = last_age;
+            }
+        }
+
+        // If we successfully got the preferences, write it out, otherwise write `0` for this `.ji` file.
+        if (prefs_hash != NULL) {
+            write_uint64(s, jl_unbox_uint64(prefs_hash));
+        } else {
+            write_uint64(s, 0);
+        }
+
         // write a dummy file position to indicate the beginning of the source-text
         pos = ios_pos(s);
         ios_seek(s, initial_pos);

stdlib/CompilePreferences/Project.toml

@@ -0,0 +1,12 @@
+name = "CompilePreferences"
+uuid = "21216c6a-2e73-6563-6e65-726566657250"
+
+[deps]
+TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
+
+[extras]
+Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+
+[targets]
+test = ["Test", "Pkg"]

stdlib/CompilePreferences/docs/src/index.md

@@ -0,0 +1,46 @@
+# CompilePreferences
+
+!!! compat "Julia 1.6"
+    Julia's `CompilePreferences` API requires at least Julia 1.6.
+
+`CompilePreferences` support embedding a simple `Dict` of metadata for a package on a per-project basis.  These preferences allow for packages to set simple, persistent pieces of data that the user has selected, that can persist across multiple versions of a package.
+
+## API Overview
+
+`CompilePreferences` are used primarily through the `@load_preferences`, `@save_preferences` and `@modify_preferences` macros.  These macros will auto-detect the UUID of the calling package, throwing an error if the calling module does not belong to a package.  The function forms can be used to load, save or modify preferences belonging to another package.
+
+Example usage:
+
+```julia
+using CompilePreferences
+
+function get_preferred_backend()
+    prefs = @load_preferences()
+    return get(prefs, "backend", "native")
+end
+
+function set_backend(new_backend)
+    @modify_preferences!() do prefs
+        prefs["backend"] = new_backend
+    end
+end
+```
+
+By default, preferences are stored within the `Project.toml` file of the currently-active project, and as such all new projects will start from a blank state, with all preferences being un-set.
+Package authors that wish to have a default value set for their preferences should use the `get(prefs, key, default)` pattern as shown in the code example above.
+
+# API Reference
+
+!!! compat "Julia 1.6"
+    Julia's `CompilePreferences` API requires at least Julia 1.6.
+
+```@docs
+CompilePreferences.load_preferences
+CompilePreferences.@load_preferences
+CompilePreferences.save_preferences!
+CompilePreferences.@save_preferences!
+CompilePreferences.modify_preferences!
+CompilePreferences.@modify_preferences!
+CompilePreferences.clear_preferences!
+CompilePreferences.@clear_preferences!
+```