enable completions for identifiers following ! operator (#34182)

Author: aviatesk

stdlib/REPL/src/REPLCompletions.jl

@@ -612,7 +612,9 @@ function completions(string, pos, context_module=Main)::Completions
     inc_tag==:string && return String[], 0:-1, false
     if inc_tag === :other && should_method_complete(partial)
         frange, method_name_end = find_start_brace(partial)
-        ex = Meta.parse(partial[frange] * ")", raise=false, depwarn=false)
+        # strip preceding ! operator
+        s = replace(partial[frange], r"\!+([^=\(]+)" => s"\1")
+        ex = Meta.parse(s * ")", raise=false, depwarn=false)
 
         if isa(ex, Expr)
             if ex.head==:call
@@ -627,6 +629,10 @@ function completions(string, pos, context_module=Main)::Completions
 
     dotpos = something(findprev(isequal('.'), string, pos), 0)
     startpos = nextind(string, something(findprev(in(non_identifier_chars), string, pos), 0))
+    # strip preceding ! operator
+    if (m = match(r"^\!+", string[startpos:pos])) !== nothing
+        startpos += length(m.match)
+    end
 
     ffunc = (mod,x)->true
     suggestions = Completion[]

stdlib/REPL/test/replcompletions.jl

@@ -138,6 +138,21 @@ let s = "Main.CompletionFoo.f"
     @test !("foobar" in c)
 end
 
+# test method completions when `!` operator precedes
+let
+    s = "!is"
+    c, r = test_complete(s)
+    @test "isa" in c
+    @test s[r] == "is"
+    @test !("!" in c)
+
+    s = "!!is"
+    c, r = test_complete(s)
+    @test "isa" in c
+    @test s[r] == "is"
+    @test !("!" in c)
+end
+
 # issue #6424
 let s = "Main.CompletionFoo.@f"
     c, r = test_complete(s)
@@ -302,6 +317,27 @@ let s = "max("
     @test s[r] == "max"
 end
 
+# test method completions when `!` operator precedes
+let
+    s = "!("
+    c, r, res = test_complete(s)
+    @test !res
+    @test all(m -> string(m) in c, methods(!))
+    @test s[r] == s[1:end-1]
+
+    s = "!isnothing("
+    c, r, res = test_complete(s)
+    @test !res
+    @test all(m -> string(m) in c, methods(isnothing))
+    @test s[r] == s[1:end-1]
+
+    s = "!!isnothing("
+    c, r, res = test_complete(s)
+    @test !res
+    @test all(m -> string(m) in c, methods(isnothing))
+    @test s[r] == s[1:end-1]
+end
+
 # Test completion of methods with input concrete args and args where typeinference determine their type
 let s = "CompletionFoo.test(1,1, "
     c, r, res = test_complete(s)