Stop at breakpoints on a function's initial statements

src/Debugger.jl

@@ -97,7 +97,12 @@ function _make_frame(mod, arg)
         frame === nothing && error("failed to enter the function, perhaps it is set to run in compiled mode")
         frame = JuliaInterpreter.maybe_step_through_kwprep!(frame)
         frame = JuliaInterpreter.maybe_step_through_wrapper!(frame)
-        JuliaInterpreter.maybe_next_call!(frame)
+        # Advance to the first call, but stop earlier if a breakpoint is set on
+        # one of the initial statements (#134)
+        JuliaInterpreter.maybe_next_until!(frame) do fr
+            JuliaInterpreter.shouldbreak(fr, fr.pc) ||
+                JuliaInterpreter.is_call_or_return(JuliaInterpreter.pc_expr(fr))
+        end
         frame
     end
 end

src/repl.jl

@@ -155,7 +155,9 @@ function RunDebugger(frame, repl = nothing, terminal = nothing; initial_continue
     state.standard_keymap = keymaps
     panel.keymap_dict = LineEdit.keymap([repl_switch;state.standard_keymap])
 
-    if initial_continue
+    # If a breakpoint is set on the statement we are already stopped at, `c` would
+    # step over it, so stay put and show the prompt instead (#134)
+    if initial_continue && !JuliaInterpreter.shouldbreak(state.frame, state.frame.pc)
         try
             execute_command(state, Val(:c), "c")
         catch err

test/misc.jl

@@ -225,6 +225,22 @@ execute_command(state, Val{:bp}(), """bp add lfdshfds""")
     @test !_iscall(:(identity() do; end))
 end
 
+# Issue #134: a breakpoint on one of the initial statements of a function should
+# not be stepped over when entering the frame
+@testset "breakpoint on first statement" begin
+    function f_bp_first(x)
+        y = x + 1
+        return y * 2
+    end
+    JuliaInterpreter.breakpoint(f_bp_first)
+    try
+        frame = @make_frame f_bp_first(1)
+        @test JuliaInterpreter.shouldbreak(frame, frame.pc)
+    finally
+        JuliaInterpreter.remove()
+    end
+end
+
 # Issue #394: backslash (latex) completions in the evaluation mode
 @testset "completions" begin
     f_completions(x) = x + 1

test/ui.jl

@@ -140,12 +140,12 @@ end
                     Vector{UInt8}(codeunits(actual_decorator)))
             end
 
-            function run_terminal_test(frame, commands, validation)
+            function run_terminal_test(frame, commands, validation; initial_continue=false)
                 run_debugger = function (emuterm)
                     repl = REPL.LineEditREPL(emuterm, true)
                     repl.interface = REPL.setup_interface(repl)
                     repl.specialdisplay = REPL.REPLDisplay(repl)
-                    RunDebugger(frame, repl, emuterm)
+                    RunDebugger(frame, repl, emuterm; initial_continue=initial_continue)
                 end
                 output_path = joinpath(@__DIR__, validation)
                 if get(ENV, "DEBUGGER_UPDATE_UI_SNAPSHOTS", "false") == "true"
@@ -195,6 +195,18 @@ end
                               ["bt\n", "c\n"],
                               "ui/big_repr_ui.multiout")
 
+            # Issue #134: `@run` should stop at a breakpoint on the first statement
+            # instead of continuing past it
+            JuliaInterpreter.breakpoint(mysum)
+            try
+                run_terminal_test(@make_frame(mysum([1,2,3])),
+                                  ["c\n"],
+                                  "ui/bp_first_statement.multiout";
+                                  initial_continue=true)
+            finally
+                JuliaInterpreter.remove()
+            end
+
             was_breaking_on_error = JuliaInterpreter.break_on_error[]
             Debugger.break_on(:error)
             try

test/ui/bp_first_statement.multiout

@@ -0,0 +1,24 @@
+++++++++++++++++++++++++++++++++++++++++++++++++++
+|In mysum(x) at ui.jl:94
+|  94  function mysum(x)
+|> 95      s = 0
+|  96      for v in x
+|  97          s += v
+|  98      end
+|  99      return s
+| 100  end
+|
+|About to run: 0
+|1|debug> 
+--------------------------------------------------
+|AAAAAAAAAAAAAAAAAAAAAAA
+|AAAAAAAAAAAAAAAAAAAAAAA
+|BBBBBBAAAAAAAAA
+|AAAAAAAAAAAAAAAAAAAA
+|CCCCCCAAAAAAAAAAAAAA
+|AAAAAAAAAAAAA
+|AAAAAAAAAAAAAAAAAA
+|AAAAAAAAA
+|
+|AAAAAAAAAAAAAAA
+|DDDDDDDDD