add a way to break on throw (#253)

Author: KristofferC

src/breakpoints.jl

@@ -136,11 +136,14 @@ Turn on automatic breakpoints when any of the conditions described in `states` o
 The supported states are:
 
 - `:error`: trigger a breakpoint any time an uncaught exception is thrown
+- `:throw` : trigger a breakpoint any time a throw is executed (even if it will eventually be caught)
 """
 function break_on(states::Vararg{Symbol})
     for state in states
         if state == :error
             break_on_error[] = true
+        elseif state == :throw
+            break_on_throw[] = true
         else
             throw(ArgumentError(string("unsupported state :", state)))
         end
@@ -157,6 +160,8 @@ function break_off(states::Vararg{Symbol})
     for state in states
         if state == :error
             break_on_error[] = false
+        elseif state == :throw
+            break_on_throw[] = false
         else
             throw(ArgumentError(string("unsupported state :", state)))
         end

src/interpret.jl

@@ -560,13 +560,8 @@ 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 err_will_be_thrown_to_top_level
-            return BreakpointRef(frame.framecode, frame.pc, err)
-        end
+    if break_on_throw[] || (break_on_error[] && err_will_be_thrown_to_top_level)
+        return BreakpointRef(frame.framecode, frame.pc, err)
     end
     if isempty(data.exception_frames)
         is_root_frame = frame.caller === nothing

src/types.jl

@@ -15,6 +15,7 @@ end
 truecondition(frame) = true
 falsecondition(frame) = false
 const break_on_error = Ref(false)
+const break_on_throw = Ref(false)
 
 """
     BreakpointState(isactive=true, condition=JuliaInterpreter.truecondition)

test/breakpoints.jl

@@ -165,6 +165,18 @@ end
         v = JuliaInterpreter.finish_and_return!(frame)
         @test v isa ErrorException
         @test stacklength(frame) == 1
+
+        # Break on caught exception when enabled
+        break_on(:throw)
+        try
+            frame = JuliaInterpreter.enter_call(f_exc_outer);
+            v = JuliaInterpreter.finish_and_return!(frame)
+            @test v isa BreakpointRef
+            @test v.err isa ErrorException
+            @test v.framecode.scope == @which error()
+        finally
+            break_off(:throw)
+        end
     finally
         break_off(:error)
     end