Extend query syntax

[gomoripeti]

In order to add more functionality we need to extend the query syntax to allow more options and alternatives. (eg #108 )

Requirements:

• It must be parsable (at list tokenize, then split, then parse - this is how query processing in erlang-syntax mode already works) and have familiar syntax in both Erlang and Elixir.
• (Maybe) It also has to be generated from a list of options (oposit of parsing, one-one mapping)

1. Action-functions

One option is to extend the match-spec syntax by allowing more action-functions.

• examples

  mod:fun(_,A,_) -> argdist(A)
  mod:fun(_,A,B) -> argdist(A+B)
  mod:fun(_,A,_) -> argdist(A >= 0, enum)
  mod:fun(_,A,_) -> argdist(A >= 0, [{enum, 2}, {interval, 5}])
  
  mod:fun(_,_,_) when caller(mod2,fun2,_)

• advantages: compact, allows some small sugars in the match-spec (like caller guard)
• disadvantage: limited, what if a feature does not work on mfas at all (eg gc profiling)

2. Record/Struct/Keyword list

Other choice is to have something like records or structs:

• construction:

  • starts with a special character
  • followed by a named-command
  • then key-value pairs of named-arguments
  • last one is the match-spec (to allow special parsing)
  • no enclosing {}

• examples (multiple lines for readability)
  Erlang:

  #argdist enum = 2,
    interval = "5sec",
    derive: if A > 0 -> positive; true -> neg_or_zero end,
    mfa = mod:fun(_, A, _)
  
  #funlatency caller: xprof_core_lib:detect_mod/0, mfa : lists:keymember/3

  Elixir:

  %Argdist int: -100..100,
      interval: "5sec",
      mfa: Mod.fun(_, a, _)
  %Funlatency caller: String.split/3, mfa : Keyword.get/3

• advantage: more flexible, it is easier to generate (even on the frontend)

• disadvantage: more verbose (how will this fit in graph title?)

We can still expose the raw/parsed Erlang API:
xprof_core:monitor_pp(QueryString) would parse the query and convert into a lower level xprof_core:monitor(Command, Options) format.
Current xprof_core:monitor({Mod,Fun,Arity}) would be equal with xprof_core:monitor(funlatency, [{mfa, {Mod,Fun,Arity}}])

3. Options

Alternatively we can keep current query syntax and add option buttons/widgets on the gui. They map to a separate option list in the Erlang API.