Support printing of fictive breakpoints

A fictive breakpoint can be a useful tool in control flow, for example
passing an `exec!` method to `evaluate_call!` that returns a breakpoint.

Author: timholy

src/breakpoints.jl

@@ -27,8 +27,16 @@ end
 BreakpointRef(framecode, stmtidx) = BreakpointRef(framecode, stmtidx, nothing)
 
 function Base.show(io::IO, bp::BreakpointRef)
-    lineno = linenumber(bp.framecode, bp.stmtidx)
-    print(io, "breakpoint(", bp.framecode.scope, ", ", lineno, ')')
+    if checkbounds(Bool, bp.framecode.breakpoints, bp.stmtidx)
+        lineno = linenumber(bp.framecode, bp.stmtidx)
+        print(io, "breakpoint(", bp.framecode.scope, ", ", lineno)
+    else
+        print(io, "breakpoint(", bp.framecode.scope, ", %", bp.stmtidx)
+    end
+    if bp.err !== nothing
+        print(io, ", ", bp.err)
+    end
+    print(io, ')')
 end
 
 const _breakpoints = BreakpointRef[]

test/breakpoints.jl

@@ -99,4 +99,17 @@ end
     finally
         JuliaInterpreter.break_on_error[] = false
     end
+
+    # Breakpoint display
+    io = IOBuffer()
+    frame = JuliaInterpreter.enter_call(loop_radius2, 2)
+    bp = JuliaInterpreter.BreakpointRef(frame.code, 1)
+    show(io, bp)
+    @test String(take!(io)) == "breakpoint(loop_radius2(n) in $(@__MODULE__) at $(@__FILE__):3, 3)"
+    bp = JuliaInterpreter.BreakpointRef(frame.code, 0)  # fictive breakpoint
+    show(io, bp)
+    @test String(take!(io)) == "breakpoint(loop_radius2(n) in $(@__MODULE__) at $(@__FILE__):3, %0)"
+    bp = JuliaInterpreter.BreakpointRef(frame.code, 1, ArgumentError("whoops"))
+    show(io, bp)
+    @test String(take!(io)) == "breakpoint(loop_radius2(n) in $(@__MODULE__) at $(@__FILE__):3, 3, ArgumentError(\"whoops\"))"
 end