only unlink frames if exception will not be thrown to top level (#214)

* only unlink frames if exception will not be thrown to top level

* Update src/interpret.jl

Co-Authored-By: KristofferC <[email protected]>

* put less in try

Author: KristofferC

src/interpret.jl

@@ -555,16 +555,18 @@ behaviors:
 """
 function handle_err(@nospecialize(recurse), frame, err)
     data = frame.framedata
+    err_will_be_thrown_to_top_level = isempty(data.exception_frames) && !data.caller_will_catch_err
     if break_on_error[]
         # See if the current frame or a frame in the stack will catch this exception,
         # otherwise this exception would have been thrown to the user and we should
         # return a breakpoint
-        if isempty(data.exception_frames) && !data.caller_will_catch_err
+        if err_will_be_thrown_to_top_level
             return BreakpointRef(frame.framecode, frame.pc, err)
         end
     end
     if isempty(data.exception_frames)
-        if frame.caller !== nothing
+        is_root_frame = frame.caller === nothing
+        if !is_root_frame && !err_will_be_thrown_to_top_level
             frame.caller.callee = nothing
             recycle(frame)
         end

test/debug.jl

@@ -278,7 +278,7 @@ struct B{T} end
         g_inner() = error()
         fr = JuliaInterpreter.enter_call(f_outer)
         @test_throws ErrorException debug_command(fr, :finish)
-        @test stacklength(fr) == 1
+        @test stacklength(fr) == 3
 
         # Break on error
         try
@@ -424,4 +424,21 @@ struct B{T} end
         frame, pc = debug_command(frame, :si)
         @test frame.pc == 1
     end
+
+
+    @testset "preservation of stack when throwing to toplevel" begin
+        f() = "αβ"[2]
+        frame1 = JuliaInterpreter.enter_call(f);
+        err = try debug_command(frame1, :c)
+        catch err
+            err
+        end
+        try
+            break_on(:error)
+            frame2, pc = @interpret f()
+            @test leaf(frame2).framecode.scope === leaf(frame1).framecode.scope
+        finally
+            break_off(:error)
+        end
+    end
 # end