Infiltrator.jl

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This packages provides the @infiltrate macro, which acts as a breakpoint with neglible runtime performance overhead.

Note that you cannot access other function scopes or step into further calls. Use an actual debugger if you need that level of flexibility.

Running code that ends up triggering the @infiltrate REPL mode via inline evaluation in VS Code or Juno can cause issues, so it's recommended to always use the REPL directly.

@infiltrate

@infiltrate cond = true

@infiltrate sets an infiltration point.

When the infiltration point is hit, it will drop you into an interactive REPL session that lets you inspect local variables and the call stack as well as execute aribtrary statements in the context of the current local and global scope.

The optional argument cond only enables this infiltration point if it evaluates to true.

You can also use

if isdefined(Main, :Infiltrator)
  Main.infiltrate(@__MODULE__, Base.@locals, @__FILE__, @__LINE__)
end

to infiltrate package code without any post-hoc evaluation into the module (because the functional form does not require Infiltrator to be loaded at compiletime).

@exfiltrate

@exfiltrate

Assigns all local variables into global storage.

The safehouse

Exfiltrating variables (with @exfiltrate or by assignment in an @infiltrate session) happens by assigning the variable to a global storage space (backed by a module); any exfiltrated objects can be directly accessed, via Infiltrator.store or its exported aliases safehouse or exfiltrated:

julia> foo(x) = @exfiltrate
foo (generic function with 1 method)

julia> foo(3)

julia> safehouse.x # or exfiltrated.x
3

You can reset the safehouse with Infiltrator.clear_store!().

You can also assign a specific module with Infiltrator.set_store!(mod). This allows you to e.g. set the backing module to Main and therefore export the contents of the safehouse to the global namespace (although doing so is not recommended).

Example usage

julia> function f(x)
         out = []
         for i in x
           push!(out, 2i)
           @infiltrate
         end
         out
       end
f (generic function with 1 method)

julia> f([1,2,3])
Infiltrating f(x::Vector{Int64})
  at REPL[10]:5

infil> ?
  Code entered here is evaluated in the current scope. Changes to local variables are not possible; global variables can only be changed with eval/@eval.

  All assignments will end up in the safehouse.

  The following commands are special cased:

    •  ?: Print this help text.

    •  @trace: Print the current stack trace.

    •  @locals: Print local variables. @locals x y only prints x and y.

    •  @exfiltrate: Save all local variables into the store. @exfiltrate x y saves x and y; this variant can also exfiltrate variables defined in the infil> REPL.

    •  @toggle: Toggle infiltrating at this @infiltrate spot (clear all with Infiltrator.clear_disabled!()).

    •  @continue: Continue to the next infiltration point or exit (shortcut: Ctrl-D).

    •  @doc symbol: Get help for symbol (same as in the normal Julia REPL).

    •  @exit: Stop infiltrating for the remainder of this session and exit (on Julia versions prior to 1.5 this needs to be manually cleared with Infiltrator.end_session!()).

infil> @locals
- out::Vector{Any} = Any[2]
- i::Int64 = 1
- x::Vector{Int64} = [1, 2, 3]

infil> 0//0
ERROR: ArgumentError: invalid rational: zero(Int64)//zero(Int64)
Stacktrace:
 [1] __throw_rational_argerror_zero(T::Type)
   @ Base ./rational.jl:32
 [2] Rational{Int64}(num::Int64, den::Int64)
   @ Base ./rational.jl:34
 [3] Rational
   @ ./rational.jl:39 [inlined]
 [4] //(n::Int64, d::Int64)
   @ Base ./rational.jl:62
 [5] top-level scope
   @ none:1

infil> @toggle
Disabled infiltration at this infiltration point.

infil> @toggle
Enabled infiltration at this infiltration point.

infil> @continue

Infiltrating f(x::Vector{Int64})
  at REPL[10]:5

infil> intermediate = copy(out)
2-element Vector{Any}:
 2
 4

infil> @exfiltrate intermediate x
Exfiltrating 2 local variables into the safehouse.

infil> @exit

3-element Vector{Any}:
 2
 4
 6

julia> safehouse.intermediate
2-element Vector{Any}:
 2
 4

julia> @withstore begin
         x = 23
         x .* intermediate
       end
2-element Vector{Int64}:
 46
 92