[REPLCompletions] allow symbol completions within incomplete macrocall expression (#51834)

fix #51827

---------

Co-authored-by: Kristoffer Carlsson <kcarlsson89@gmail.com>
(cherry picked from commit 3b1ba62)

Author: aviatesk

stdlib/REPL/src/REPLCompletions.jl

@@ -1041,6 +1041,11 @@ function complete_identifiers!(suggestions::Vector{Completion}, @nospecialize(ff
             if isinfix
                 ex = ex.args[end]
             end
+        elseif isexpr(ex, :macrocall) && length(ex.args) > 1
+            # allow symbol completions within potentially incomplete macrocalls
+            if s[end] ≠ '`' && s[end] ≠ ')'
+                ex = ex.args[end]
+            end
         end
     end
     append!(suggestions, complete_symbol(ex, name, ffunc, context_module))

stdlib/REPL/test/replcompletions.jl

@@ -1920,3 +1920,15 @@ for (s, compl) in (("2*CompletionFoo.nam", "named"),
     c, r = test_complete(s)
     @test only(c) == compl
 end
+
+# allows symbol completion within incomplete :macrocall
+# https://github.com/JuliaLang/julia/issues/51827
+macro issue51827(args...)
+    length(args) ≥ 2 || error("@issue51827: incomplete arguments")
+    return args
+end
+let s = "@issue51827 Base.ac"
+    c, r, res = test_complete_context(s)
+    @test res
+    @test "acquire" in c
+end