error.jl

# This file is a part of Julia. License is MIT: https://julialang.org/license

# pseudo-definitions to show how everything behaves
#
# throw(label, val) = # throw a value to a dynamically enclosing block
#
# function rethrow(val)
#     global current_exception = val
#     throw(current_handler(), current_exception)
# end
#
# rethrow() = rethrow(current_exception)
#
# function throw(val)
#     global catch_backtrace = backtrace()
#     rethrow(val)
# end

"""
    throw(e)

Throw an object as an exception.
"""
throw

## native julia error handling ##

"""
    error(message::AbstractString)

Raise an `ErrorException` with the given message.
"""
error(s::AbstractString) = throw(ErrorException(s))

"""
    error(msg...)

Raise an `ErrorException` with the given message.
"""
function error(s::Vararg{Any,N}) where {N}
    @_noinline_meta
    throw(ErrorException(Main.Base.string(s...)))
end

"""
    rethrow([e])

Throw an object without changing the current exception backtrace. The default argument is
the current exception (if called within a `catch` block).
"""
rethrow() = ccall(:jl_rethrow, Bottom, ())
rethrow(e) = ccall(:jl_rethrow_other, Bottom, (Any,), e)

struct InterpreterIP
    code::Union{CodeInfo,Core.MethodInstance,Nothing}
    stmt::Csize_t
end

# convert dual arrays (ips, interpreter_frames) to a single array of locations
function _reformat_bt(bt, bt2)
    ret = Vector{Union{InterpreterIP,Ptr{Cvoid}}}()
    i, j = 1, 1
    while i <= length(bt)
        ip = bt[i]::Ptr{Cvoid}
        if ip == Ptr{Cvoid}(-1%UInt)
            # The next one is really a CodeInfo
            push!(ret, InterpreterIP(
                bt2[j],
                bt[i+2]))
            j += 1
            i += 3
        else
            push!(ret, Ptr{Cvoid}(ip))
            i += 1
        end
    end
    ret
end

function backtrace end

"""
    catch_backtrace()

Get the backtrace of the current exception, for use within `catch` blocks.
"""
function catch_backtrace()
    bt = Ref{Any}(nothing)
    bt2 = Ref{Any}(nothing)
    ccall(:jl_get_backtrace, Cvoid, (Ref{Any}, Ref{Any}), bt, bt2)
    return _reformat_bt(bt[], bt2[])
end

"""
    catch_stack(task=current_task(); [inclue_bt=true])

Get the stack of exceptions currently being handled. For nested catch blocks
there may be more than one current exception in which case the most recently
thrown exception is last in the stack. The stack is returned as a Vector of
`(exception,backtrace)` pairs, or a Vector of exceptions if `include_bt` is
false.

Explicitly passing `task` will return the current exception stack on an
arbitrary task. This is useful for inspecting tasks which have failed due to
uncaught exceptions.

!!! compat "Julia 1.1"
    This function is experimental in Julia 1.1 and will likely be renamed in a
    future release (see https://github.com/JuliaLang/julia/pull/29901).
"""
function catch_stack(task=current_task(); include_bt=true)
    raw = ccall(:jl_get_excstack, Any, (Any,Cint,Cint), task, include_bt, typemax(Cint))
    formatted = Any[]
    stride = include_bt ? 3 : 1
    for i = reverse(1:stride:length(raw))
        e = raw[i]
        push!(formatted, include_bt ? (e,Base._reformat_bt(raw[i+1],raw[i+2])) : e)
    end
    formatted
end

## keyword arg lowering generates calls to this ##
function kwerr(kw, args::Vararg{Any,N}) where {N}
    @_noinline_meta
    throw(MethodError(typeof(args[1]).name.mt.kwsorter, (kw,args...)))
end

## system error handling ##
"""
    systemerror(sysfunc, iftrue)

Raises a `SystemError` for `errno` with the descriptive string `sysfunc` if `iftrue` is `true`
"""
systemerror(p, b::Bool; extrainfo=nothing) = b ? throw(Main.Base.SystemError(string(p), Libc.errno(), extrainfo)) : nothing


## system errors from Windows API functions
struct WindowsErrorInfo
    errnum::UInt32
    extrainfo
end
"""
    windowserror(sysfunc, iftrue)

Like [`systemerror`](@ref), but for Windows API functions that use [`GetLastError`](@ref) instead
of setting [`errno`](@ref).
"""
windowserror(p, b::Bool; extrainfo=nothing) = b ? throw(Main.Base.SystemError(string(p), Libc.errno(), WindowsErrorInfo(Libc.GetLastError(), extrainfo))) : nothing


## assertion macro ##


"""
    @assert cond [text]

Throw an [`AssertionError`](@ref) if `cond` is `false`. Preferred syntax for writing assertions.
Message `text` is optionally displayed upon assertion failure.

!!! warning
    An assert might be disabled at various optimization levels.
    Assert should therefore only be used as a debugging tool
    and not used for authentication verification (e.g., verifying passwords),
    nor should side effects needed for the function to work correctly
    be used inside of asserts.

# Examples
```jldoctest
julia> @assert iseven(3) "3 is an odd number!"
ERROR: AssertionError: 3 is an odd number!

julia> @assert isodd(3) "What even are numbers?"
```
"""
macro assert(ex, msgs...)
    msg = isempty(msgs) ? ex : msgs[1]
    if isa(msg, AbstractString)
        msg = msg # pass-through
    elseif !isempty(msgs) && (isa(msg, Expr) || isa(msg, Symbol))
        # message is an expression needing evaluating
        msg = :(Main.Base.string($(esc(msg))))
    elseif isdefined(Main, :Base) && isdefined(Main.Base, :string) && applicable(Main.Base.string, msg)
        msg = Main.Base.string(msg)
    else
        # string() might not be defined during bootstrap
        msg = quote
            msg = $(Expr(:quote,msg))
            isdefined(Main, :Base) ? Main.Base.string(msg) :
                (Core.println(msg); "Error during bootstrap. See stdout.")
        end
    end
    return :($(esc(ex)) ? $(nothing) : throw(AssertionError($msg)))
end

struct ExponentialBackOff
    n::Int
    first_delay::Float64
    max_delay::Float64
    factor::Float64
    jitter::Float64

    function ExponentialBackOff(n, first_delay, max_delay, factor, jitter)
        all(x->x>=0, (n, first_delay, max_delay, factor, jitter)) || error("all inputs must be non-negative")
        new(n, first_delay, max_delay, factor, jitter)
    end
end

"""
    ExponentialBackOff(; n=1, first_delay=0.05, max_delay=10.0, factor=5.0, jitter=0.1)

A [`Float64`](@ref) iterator of length `n` whose elements exponentially increase at a
rate in the interval `factor` * (1 ± `jitter`).  The first element is
`first_delay` and all elements are clamped to `max_delay`.
"""
ExponentialBackOff(; n=1, first_delay=0.05, max_delay=10.0, factor=5.0, jitter=0.1) =
    ExponentialBackOff(n, first_delay, max_delay, factor, jitter)
function iterate(ebo::ExponentialBackOff, state= (ebo.n, min(ebo.first_delay, ebo.max_delay)))
    state[1] < 1 && return nothing
    next_n = state[1]-1
    curr_delay = state[2]
    next_delay = min(ebo.max_delay, state[2] * ebo.factor * (1.0 - ebo.jitter + (rand(Float64) * 2.0 * ebo.jitter)))
    (curr_delay, (next_n, next_delay))
end
length(ebo::ExponentialBackOff) = ebo.n
eltype(::Type{ExponentialBackOff}) = Float64

"""
    retry(f;  delays=ExponentialBackOff(), check=nothing) -> Function

Return an anonymous function that calls function `f`.  If an exception arises,
`f` is repeatedly called again, each time `check` returns `true`, after waiting the
number of seconds specified in `delays`.  `check` should input `delays`'s
current state and the `Exception`.

!!! compat "Julia 1.2"
    Before Julia 1.2 this signature was restricted to `f::Function`.

# Examples
```julia
retry(f, delays=fill(5.0, 3))
retry(f, delays=rand(5:10, 2))
retry(f, delays=Base.ExponentialBackOff(n=3, first_delay=5, max_delay=1000))
retry(http_get, check=(s,e)->e.status == "503")(url)
retry(read, check=(s,e)->isa(e, IOError))(io, 128; all=false)
```
"""
function retry(f;  delays=ExponentialBackOff(), check=nothing)
    (args...; kwargs...) -> begin
        y = iterate(delays)
        while y !== nothing
            (delay, state) = y
            try
                return f(args...; kwargs...)
            catch e
                y === nothing && rethrow()
                if check !== nothing
                    result = check(state, e)
                    state, retry_or_not = length(result) == 2 ? result : (state, result)
                    retry_or_not || rethrow()
                end
            end
            sleep(delay)
            y = iterate(delays, state)
        end
        # When delays is out, just run the function without try/catch
        return f(args...; kwargs...)
    end
end