add @locals macro for obtaining dictionary of local vars and values (…

…#29733)

implements #29366

NEWS.md

@@ -5,6 +5,8 @@ New language features
 ---------------------
 
  * An *exception stack* is maintained on each task to make exception handling more robust and enable root cause analysis using `catch_stack` ([#28878]).
+ * The experimental macro `Base.@locals` returns a dictionary of current local variable names
+ and values ([#29733]).
 
 Language changes
 ----------------

base/reflection.jl

@@ -250,6 +250,42 @@ macro isdefined(s::Symbol)
  return Expr(:isdefined, esc(s))
 end
 
+"""
+ @locals()
+
+Construct a dictionary of the names (as symbols) and values of all local
+variables defined as of the call site.
+
+# Examples
+```jldoctest
+julia> let x = 1, y = 2
+ Base.@locals
+ end
+Dict{Symbol,Any} with 2 entries:
+ :y => 2
+ :x => 1
+
+julia> function f(x)
+ local y
+ show(Base.@locals); println()
+ for i = 1:1
+ show(Base.@locals); println()
+ end
+ y = 2
+ show(Base.@locals); println()
+ nothing
+ end;
+
+julia> f(42)
+Dict{Symbol,Any}(:x=>42)
+Dict{Symbol,Any}(:i=>1,:x=>42)
+Dict{Symbol,Any}(:y=>2,:x=>42)
+```
+"""
+macro locals()
+ return Expr(:locals)
+end
+
 """
  objectid(x)
 

src/julia-syntax.scm

@@ -2442,6 +2442,27 @@
  (if (not (memq (cadr e) env))
  (error "no outer local variable declaration exists for \"for outer\""))
  '(null))
+ ((eq? (car e) 'locals)
+ (let* ((names (filter (lambda (v)
+ (and (not (gensym? v))
+ (not (length= (string-split (string v) "#") 2))
+ (let ((r (assq v renames)))
+ (or (atom? r)
+ (let ((mapping (cdr r)))
+ (not (and (pair? mapping)
+ (eq? (car mapping) 'outerref))))))))
+ env))
+ (names (delete-duplicates
+ (filter (lambda (v) (not (eq? v '||)))
+ (map unmangled-name names))))
+ (d (make-ssavalue)))
+ `(block (= ,d (call (call (core apply_type) (top Dict) (core Symbol) (core Any))))
+ ,@(map (lambda (v)
+ (let ((var (resolve-scopes- v env implicitglobals lam renames newlam sp)))
+ `(if (isdefined ,var)
+ (call (top setindex!) ,d ,var (quote ,v)))))
+ names)
+ ,d)))
  ((eq? (car e) 'lambda)
  (let* ((lv (lam:vars e))
  (env (append lv env))
@@ -2494,6 +2515,7 @@
  (new-renames (append (map cons need-rename renamed) ;; map from definition name -> gensym name
  (map cons need-rename-def renamed-def)
  (map (lambda (g) (cons g `(outerref ,g))) new-iglo)
+ (map (lambda (g) (cons g `(outerref ,g))) glob)
  (filter (lambda (ren) ;; old renames list, with anything in vars removed
  (let ((var (car ren)))
  (not (or (memq var all-vars) ;; remove anything new

test/reflection.jl

@@ -813,3 +813,36 @@ f20872(::Val, ::Val) = false
 module M29962 end
 # make sure checking if a binding is deprecated does not resolve it
 @test !Base.isdeprecated(M29962, :sin) && !Base.isbindingresolved(M29962, :sin)
+
+# @locals
+using Base: @locals
+let
+ local x, y
+ global z
+ @test isempty(keys(@locals))
+ x = 1
+ @test @locals() == Dict{Symbol,Any}(:x=>1)
+ y = ""
+ @test @locals() == Dict{Symbol,Any}(:x=>1,:y=>"")
+ for i = 8:8
+ @test @locals() == Dict{Symbol,Any}(:x=>1,:y=>"",:i=>8)
+ end
+ for i = 42:42
+ local x
+ @test @locals() == Dict{Symbol,Any}(:y=>"",:i=>42)
+ end
+ @test @locals() == Dict{Symbol,Any}(:x=>1,:y=>"")
+ x = (y,)
+ @test @locals() == Dict{Symbol,Any}(:x=>("",),:y=>"")
+end
+
+function _test_at_locals1(::Any, ::Any)
+ x = 1
+ @test @locals() == Dict{Symbol,Any}(:x=>1)
+end
+_test_at_locals1(1,1)
+function _test_at_locals2(a::Any, ::Any)
+ x = 2
+ @test @locals() == Dict{Symbol,Any}(:x=>2,:a=>a)
+end
+_test_at_locals2(1,1)