add support for watchers (#49)

* add watchers

Author: KristofferC

README.md

@@ -41,6 +41,10 @@ Basic Commands:
 - ``` `stuff ```: run `stuff` in the current function's context
 - `fr [v::Int]`: show all variables in the current function, `v` defaults to `1`
 - `f [n::Int]`: go to the `n`-th function in the call stack
+- `w`
+    - `w add expr`: add an expression to the watch list
+    - `w`: show all watch expressions evaluated in the current function's context
+    - `w rm [i::Int]`: remove all or the `i`:th watch expression
 - `q`: quit the debugger, returning `nothing`
 
 Advanced commands:

src/Debugger.jl

@@ -31,18 +31,23 @@ export @bp, @breakpoint, breakpoint
 include("LineNumbers.jl")
 using .LineNumbers: SourceFile, compute_line
 
+# We make WATCH_LIST a global since it is likely useful to keep
+# watch expressions between invocations of the debugger interface
+const WATCH_LIST = []
+
 mutable struct DebuggerState
     frame::Union{Nothing, Frame}
     level::Int
     broke_on_error::Bool
+    watch_list::Vector
     repl
     terminal
     main_mode
     julia_prompt::Ref{LineEdit.Prompt}
     standard_keymap
     overall_result
 end
-DebuggerState(stack, repl, terminal) = DebuggerState(stack, 1, false, repl, terminal, nothing, Ref{LineEdit.Prompt}(), nothing, nothing)
+DebuggerState(stack, repl, terminal) = DebuggerState(stack, 1, false, WATCH_LIST, repl, terminal, nothing, Ref{LineEdit.Prompt}(), nothing, nothing)
 DebuggerState(stack, repl) = DebuggerState(stack, repl, nothing)
 
 function active_frame(state)
@@ -60,6 +65,7 @@ include("locationinfo.jl")
 include("repl.jl")
 include("commands.jl")
 include("printing.jl")
+include("watch.jl")
 
 function _make_frame(mod, arg)
     args = try

src/commands.jl

@@ -98,6 +98,34 @@ function execute_command(state::DebuggerState, ::Union{Val{:f}, Val{:fr}}, cmd)
     end
 end
 
+function execute_command(state::DebuggerState, ::Val{:w}, cmd::AbstractString)
+    # TODO show some info messages?
+    cmds = split(cmd)
+    if length(cmds) == 1
+        io = Base.pipe_writer(state.terminal)
+        show_watch_list(io, state)
+        return false
+    elseif length(cmds) >= 2
+        if cmds[2] == "rm"
+            if length(cmds) == 2
+                clear_watch_list!(state)
+                return false
+            elseif length(cmds) == 3
+                i = parse(Int, cmds[3])
+                clear_watch_list!(state, i)
+                return false
+            end
+        end
+        if cmds[2] == "add"
+            if add_watch_entry!(state, join(cmds[3:end]))
+            end
+            return false
+        end
+    end
+    # Error
+    return execute_command(state, Val(:_), cmd)
+end
+
 function execute_command(state::DebuggerState, _, cmd)
     println("Unknown command `$cmd`. Executing `?` to obtain help.")
     execute_command(state, Val{Symbol("?")}(), "?")
@@ -116,6 +144,10 @@ function execute_command(state::DebuggerState, ::Val{:?}, cmd::AbstractString)
     - ``` `stuff ```: run `stuff` in the current function's context\\
     - `fr [v::Int]`: show all variables in the current frame, `v` defaults to `1`\\
     - `f [n::Int]`: go to the `n`-th frame\\
+    - `w`\\
+        - `w add expr`: add an expression to the watch list\\
+        - `w`: show all watch expressions evaluated in the current function's context\\
+        - `w rm [i::Int]`: remove all or the `i`:th watch expression\\
     - `q`: quit the debugger, returning `nothing`\\
     Advanced commands:\\
     - `nc`: step to the next call\\

src/printing.jl

@@ -48,7 +48,7 @@ function print_next_expr(io::IO, frame::Frame)
     end
     if isexpr(expr, :call) || isexpr(expr, :return)
         for i in 1:length(expr.args)
-            val = try 
+            val = try
                 @lookup(frame, expr.args[i])
             catch err
                 err isa UndefVarError || rethrow(err)

src/repl.jl

@@ -73,7 +73,7 @@ function RunDebugger(frame, repl = Base.active_repl, terminal = Base.active_repl
 
     state.standard_keymap = Dict{Any,Any}[skeymap, LineEdit.history_keymap, LineEdit.default_keymap, LineEdit.escape_defaults]
     panel.keymap_dict = LineEdit.keymap([repl_switch;state.standard_keymap])
-    
+
     if initial_continue
         execute_command(state, Val(:c), "c")
         state.frame === nothing && return state.overall_result

src/watch.jl

@@ -0,0 +1,47 @@
+function add_watch_entry!(state::DebuggerState, cmd::AbstractString)
+    expr = Base.parse_input_line(cmd)
+    if isexpr(expr, :error) || isexpr(expr, :incomplete)
+        printstyled(stderr, "ERROR: syntax: ", expr.args[1], "\n", color=Base.error_color())
+        return false
+    end
+    isexpr(expr, :toplevel) && (expr = expr.args[end])
+    push!(state.watch_list, expr)
+    return true
+end
+
+function show_watch_list(io, state::DebuggerState)
+    frame = active_frame(state)
+    outbuf = IOContext(IOBuffer(), io)
+
+    for (i, expr) in enumerate(state.watch_list)
+        vars = filter(v -> v.name != Symbol(""), JuliaInterpreter.locals(frame))
+        eval_expr = Expr(:let,
+            Expr(:block, map(x->Expr(:(=), x...), [(v.name, v.value) for v in vars])...),
+            expr)
+        errored = false
+        res = try
+            Core.eval(moduleof(frame), eval_expr)
+        catch err
+            errored = true
+            err
+        end
+        expr_str = highlight_code(string(expr); context=io) # Should maybe use repr here in some cases (strings)
+        if errored
+            res_str = sprint((io, args...) -> printstyled(io, args...; color=Base.error_color()), res; context=io)
+        else
+            res_str = highlight_code(repr(res), context=io)
+        end
+        print(outbuf, "$i] $(expr_str): $(res_str)\n")
+    end
+    print(io, String(take!(outbuf.io)))
+    println(io)
+end
+
+clear_watch_list!(state::DebuggerState) = empty!(state.watch_list)
+function clear_watch_list!(state::DebuggerState, i::Int)
+    if !checkbounds(Bool, state.watch_list, i)
+        printstyled(stderr, "ERROR: watch entry $i does not exist\n\n"; color=Base.error_color())
+        return
+    end
+    deleteat!(state.watch_list, i)
+end

test/ui.jl

@@ -68,6 +68,7 @@ end
 
         run_terminal_test(@make_frame(my_gcd(10, 20)),
                           ["n\n","`", "my_gc\t\n", "a\n", UP_ARROW, UP_ARROW, UP_ARROW, CTRL_C, 
+                           "w add a\n", "w add sin(a)\n", "w add b\n", "w\n", "w rm 1\n", "w\n",
                            "bt\n", "st\n", "c\n", "c\n"],
                           "ui/history_gcd.multiout")