Clean up fixed world age mechanism to use closures (JuliaLang/JuliaSyntax.jl#290)

Using a closure here to hold the fixed world age seems nicer than a
global within the JuliaSyntax module.

Author: c42f

JuliaSyntax/src/hooks.jl

@@ -76,10 +76,10 @@ function _incomplete_tag(n::SyntaxNode, codelen)
 end
 
 #-------------------------------------------------------------------------------
-if isdefined(Core, :_setparser!)
-    const _set_core_parse_hook = Core._setparser!
-else
-    function _set_core_parse_hook(parser)
+function _set_core_parse_hook(parser)
+    @static if isdefined(Core, :_setparser!)
+        Core._setparser!(parser)
+    else
         # HACK! Fool the runtime into allowing us to set Core._parse, even during
         # incremental compilation. (Ideally we'd just arrange for Core._parse to be
         # set to the JuliaSyntax parser. But how do we signal that to the dumping
@@ -100,28 +100,23 @@ else
     end
 end
 
-# Use caller's world age.
-const _latest_world = typemax(UInt)
-const _parser_world_age = Ref{UInt}(_latest_world)
 
-function core_parser_hook(code, filename, lineno, offset, options)
-    # NB: We need an inference barrier of one type or another here to prevent
-    # invalidations. The invokes provide this currently.
-    if _parser_world_age[] != _latest_world
-        Base.invoke_in_world(_parser_world_age[], _core_parser_hook,
-                             code, filename, lineno, offset, options)
+# Wrap the function `f` so that it's always invoked in the given `world_age`
+#
+# NB: We need an inference barrier of one type or another here to prevent
+# invalidations. The invokes provide this currently.
+function fix_world_age(f, world_age::UInt)
+    if world_age == typemax(UInt)
+        function invoke_latestworld(args...; kws...)
+            Base.invokelatest(f, args...; kws...)
+        end
     else
-        Base.invokelatest(_core_parser_hook, code, filename, lineno, offset, options)
+        function invoke_fixedworld(args...; kws...)
+            Base.invoke_in_world(world_age, f, args...; kws...)
+        end
     end
 end
 
-# Core._parse gained a `lineno` argument in
-# https://github.com/JuliaLang/julia/pull/43876
-# Prior to this, the following signature was needed:
-function core_parser_hook(code, filename, offset, options)
-    core_parser_hook(code, filename, 1, offset, options)
-end
-
 function _has_nested_error(ex)
     if ex isa Expr
         if ex.head == :error
@@ -137,7 +132,7 @@ end
 # Debug log file for dumping parsed code
 const _debug_log = Ref{Union{Nothing,IO}}(nothing)
 
-function _core_parser_hook(code, filename::String, lineno::Int, offset::Int, options::Symbol)
+function core_parser_hook(code, filename::String, lineno::Int, offset::Int, options::Symbol)
     try
         # TODO: Check that we do all this input wrangling without copying the
         # code buffer
@@ -266,6 +261,13 @@ function _core_parser_hook(code, filename::String, lineno::Int, offset::Int, opt
     end
 end
 
+# Core._parse gained a `lineno` argument in
+# https://github.com/JuliaLang/julia/pull/43876
+# Prior to this, the following signature was needed:
+function core_parser_hook(code, filename, offset, options)
+    core_parser_hook(code, filename, 1, offset, options)
+end
+
 # Hack:
 # Meta.parse() attempts to construct a ParseError from a string if it receives
 # `Expr(:error)`. Add an override to the ParseError constructor to prevent this.
@@ -293,14 +295,18 @@ function enable_in_core!(enable=true; freeze_world_age = true,
     if VERSION < v"1.6"
         error("Cannot use JuliaSyntax as the main Julia parser in Julia version $VERSION < 1.6")
     end
-    _parser_world_age[] = freeze_world_age ? Base.get_world_counter() : _latest_world
     if enable && !isnothing(debug_filename)
         _debug_log[] = open(debug_filename, "w")
     elseif !enable && !isnothing(_debug_log[])
         close(_debug_log[])
         _debug_log[] = nothing
     end
-    _set_core_parse_hook(enable ? core_parser_hook : _default_parser)
+    if enable
+        world_age = freeze_world_age ? Base.get_world_counter() : typemax(UInt)
+        _set_core_parse_hook(fix_world_age(core_parser_hook, world_age))
+    else
+        _set_core_parse_hook(_default_parser)
+    end
     nothing
 end
 

JuliaSyntax/test/hooks.jl

@@ -1,36 +1,36 @@
 @testset "Hooks for Core integration" begin
     @testset "whitespace parsing" begin
-        @test JuliaSyntax._core_parser_hook("", "somefile", 1, 0, :statement) == Core.svec(nothing, 0)
-        @test JuliaSyntax._core_parser_hook("", "somefile", 1, 0, :statement) == Core.svec(nothing, 0)
+        @test JuliaSyntax.core_parser_hook("", "somefile", 1, 0, :statement) == Core.svec(nothing, 0)
+        @test JuliaSyntax.core_parser_hook("", "somefile", 1, 0, :statement) == Core.svec(nothing, 0)
 
-        @test JuliaSyntax._core_parser_hook("  ", "somefile", 1, 2, :statement) == Core.svec(nothing,2)
-        @test JuliaSyntax._core_parser_hook(" #==# ", "somefile", 1, 6, :statement) == Core.svec(nothing,6)
+        @test JuliaSyntax.core_parser_hook("  ", "somefile", 1, 2, :statement) == Core.svec(nothing,2)
+        @test JuliaSyntax.core_parser_hook(" #==# ", "somefile", 1, 6, :statement) == Core.svec(nothing,6)
 
-        @test JuliaSyntax._core_parser_hook(" x \n", "somefile", 1, 0, :statement) == Core.svec(:x,4)
-        @test JuliaSyntax._core_parser_hook(" x \n", "somefile", 1, 0, :atom)      == Core.svec(:x,2)
+        @test JuliaSyntax.core_parser_hook(" x \n", "somefile", 1, 0, :statement) == Core.svec(:x,4)
+        @test JuliaSyntax.core_parser_hook(" x \n", "somefile", 1, 0, :atom)      == Core.svec(:x,2)
     end
 
     @testset "filename and lineno" begin
-        ex = JuliaSyntax._core_parser_hook("@a", "somefile", 1, 0, :statement)[1]
+        ex = JuliaSyntax.core_parser_hook("@a", "somefile", 1, 0, :statement)[1]
         @test Meta.isexpr(ex, :macrocall)
         @test ex.args[2] == LineNumberNode(1, "somefile")
 
-        ex = JuliaSyntax._core_parser_hook("@a", "otherfile", 2, 0, :statement)[1]
+        ex = JuliaSyntax.core_parser_hook("@a", "otherfile", 2, 0, :statement)[1]
         @test ex.args[2] == LineNumberNode(2, "otherfile")
 
         # Errors also propagate file & lineno
-        err = JuliaSyntax._core_parser_hook("[x)", "f1", 1, 0, :statement)[1].args[1]
+        err = JuliaSyntax.core_parser_hook("[x)", "f1", 1, 0, :statement)[1].args[1]
         @test err isa JuliaSyntax.ParseError
         @test err.source.filename == "f1"
         @test err.source.first_line == 1
-        err = JuliaSyntax._core_parser_hook("[x)", "f2", 2, 0, :statement)[1].args[1]
+        err = JuliaSyntax.core_parser_hook("[x)", "f2", 2, 0, :statement)[1].args[1]
         @test err isa JuliaSyntax.ParseError
         @test err.source.filename == "f2"
         @test err.source.first_line == 2
     end
 
     @testset "toplevel errors" begin
-        ex = JuliaSyntax._core_parser_hook("a\nb\n[x,\ny)", "somefile", 1, 0, :all)[1]
+        ex = JuliaSyntax.core_parser_hook("a\nb\n[x,\ny)", "somefile", 1, 0, :all)[1]
         @test ex.head == :toplevel
         @test ex.args[1:5] == [
             LineNumberNode(1, "somefile"),
@@ -129,6 +129,6 @@
         JuliaSyntax.enable_in_core!(false)
 
         # Should not throw
-        @test JuliaSyntax._core_parser_hook("+=", "somefile", 1, 0, :statement)[1] isa Expr
+        @test JuliaSyntax.core_parser_hook("+=", "somefile", 1, 0, :statement)[1] isa Expr
     end
 end