From 678634474521144daeafe21e6d5418ef8ab02f3a Mon Sep 17 00:00:00 2001
From: Matt Bauman <mbauman@juliahub.com>
Date: Mon, 2 Jun 2025 10:55:07 -0400
Subject: [PATCH 1/2] Re-enable tab completion of kwargs for large method
 tables (#58012)

while testing to ensure that ~~absurdly large method tables~~ tab
completing over an abstract function call doesn't tank the performance
of the REPL

Fixes #57836

(cherry picked from commit 6f129571004beac33a5cbc4aa7cbb6fcca4f5769)
---
 stdlib/REPL/src/REPLCompletions.jl  |  8 +++++++-
 stdlib/REPL/test/replcompletions.jl | 29 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/stdlib/REPL/src/REPLCompletions.jl b/stdlib/REPL/src/REPLCompletions.jl
index 14c55c71aac63..1085e446f3d4f 100644
--- a/stdlib/REPL/src/REPLCompletions.jl
+++ b/stdlib/REPL/src/REPLCompletions.jl
@@ -1025,7 +1025,13 @@ function complete_keyword_argument(partial, last_idx, context_module)
     kwargs_flag == 2 && return fail # one of the previous kwargs is invalid
 
     methods = Completion[]
-    complete_methods!(methods, funct, Any[Vararg{Any}], kwargs_ex, MAX_METHOD_COMPLETIONS, kwargs_flag == 1)
+    # Limit kwarg completions to cases when function is concretely known; looking up
+    # matching methods for abstract functions — particularly `Any` or `Function` — can
+    # take many seconds to run over the thousands of possible methods. Note that
+    # isabstracttype would return naively return true for common constructor calls
+    # like Array, but the REPL's introspection here may know their Type{T}.
+    isconcretetype(funct) || return fail
+    complete_methods!(methods, funct, Any[Vararg{Any}], kwargs_ex, -1, arg_pos == :kwargs)
     # TODO: use args_ex instead of Any[Vararg{Any}] and only provide kwarg completion for
     # method calls compatible with the current arguments.
 
diff --git a/stdlib/REPL/test/replcompletions.jl b/stdlib/REPL/test/replcompletions.jl
index 91447efb71b9b..5e6dddc455056 100644
--- a/stdlib/REPL/test/replcompletions.jl
+++ b/stdlib/REPL/test/replcompletions.jl
@@ -2301,3 +2301,32 @@ let s = "Issue53126()."
     @test res
     @test isempty(c)
 end
+
+function g54131 end
+for i in 1:498
+    @eval g54131(::Val{$i}) = i
+end
+g54131(::Val{499}; kwarg=true) = 499*kwarg
+struct F54131; end
+Base.getproperty(::F54131, ::Symbol) = Any[cos, sin, g54131][rand(1:3)]
+f54131 = F54131()
+@testset "performance of kwarg completion with large method tables" begin
+    # The goal here is to simply ensure we aren't hitting catestrophically bad
+    # behaviors when shift isn't pressed. The difference between good and bad
+    # is on the order of tens of milliseconds vs tens of seconds; using 1 sec as
+    # a very rough canary that is hopefully robust even in the noisy CI coalmines
+    s = "g54131(kwa"
+    a, b, c = completions(s, lastindex(s), @__MODULE__, #= shift =# false)
+    @test REPLCompletions.KeywordArgumentCompletion("kwarg") in a
+    @test (@elapsed completions(s, lastindex(s), @__MODULE__, false)) < 1
+
+    s = "f54131.x("
+    a, b, c = completions(s, lastindex(s), @__MODULE__, false)
+    @test only(a) isa REPLCompletions.TextCompletion
+    @test (@elapsed completions(s, lastindex(s), @__MODULE__, false)) < 1
+
+    s = "f54131.x(kwa"
+    a, b, c = completions(s, lastindex(s), @__MODULE__, false)
+    @test_broken REPLCompletions.KeywordArgumentCompletion("kwarg") in a
+    @test (@elapsed completions(s, lastindex(s), @__MODULE__, false)) < 1
+end

From e6eb886d21bca0c1f4fbe3415d1333c373d62bda Mon Sep 17 00:00:00 2001
From: Kristoffer Carlsson <kcarlsson89@gmail.com>
Date: Tue, 8 Jul 2025 13:42:45 +0200
Subject: [PATCH 2/2] Update REPLCompletions.jl

---
 stdlib/REPL/src/REPLCompletions.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/REPL/src/REPLCompletions.jl b/stdlib/REPL/src/REPLCompletions.jl
index 1085e446f3d4f..4986f604ae38f 100644
--- a/stdlib/REPL/src/REPLCompletions.jl
+++ b/stdlib/REPL/src/REPLCompletions.jl
@@ -1031,7 +1031,7 @@ function complete_keyword_argument(partial, last_idx, context_module)
     # isabstracttype would return naively return true for common constructor calls
     # like Array, but the REPL's introspection here may know their Type{T}.
     isconcretetype(funct) || return fail
-    complete_methods!(methods, funct, Any[Vararg{Any}], kwargs_ex, -1, arg_pos == :kwargs)
+    complete_methods!(methods, funct, Any[Vararg{Any}], kwargs_ex, -1, kwargs_flag == 1)
     # TODO: use args_ex instead of Any[Vararg{Any}] and only provide kwarg completion for
     # method calls compatible with the current arguments.