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fix(stdlib): error(msg, level) blames the caller for level >= 2 #428

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39 changes: 18 additions & 21 deletions lib/lua/vm/dispatcher.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -919,7 +919,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, :discard, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -973,7 +973,7 @@ defmodule Lua.VM.Dispatcher do
# `return_one/7` skips Map.fetch! lookups and lets the BEAM
# bind everything in a single `move` per slot.
frame = {code, pc + 1, regs, upvalues, proto, cont, base, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1035,7 +1035,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, base, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1088,7 +1088,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, base, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1142,7 +1142,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, base, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1194,7 +1194,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, :discard, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1246,7 +1246,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, :discard, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1299,7 +1299,7 @@ defmodule Lua.VM.Dispatcher do
else: callee_proto

frame = {code, pc + 1, regs, upvalues, proto, cont, :discard, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1354,12 +1354,9 @@ defmodule Lua.VM.Dispatcher do
# with the same depth, and the callee starts with an empty
# open-upvalue map while the caller's rides in the frame.

# `line` is carried for shape parity with the other call opcodes and
# for tooling that reads the encoded stream; the handler never needs
# it, because a self-call can never reach the native bridge that
# attributes errors to a source line, and the frame's own line slot
# is `0` for every dispatcher-side call.
{@op_call_self, base, arg_count, result_count, name_hint, _line} ->
# `line` goes in the frame's call info, as for every call opcode, so
# `error(msg, level)` can name the line a function was called from.
{@op_call_self, base, arg_count, result_count, name_hint, line} ->
callee_regs = init_callee_regs(proto, regs, base + 1, arg_count)

callee_proto =
Expand All @@ -1375,7 +1372,7 @@ defmodule Lua.VM.Dispatcher do
end

frame = {code, pc + 1, regs, upvalues, proto, cont, dest, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -1866,7 +1863,7 @@ defmodule Lua.VM.Dispatcher do
end

frame = {code, pc + 1, regs, upvalues, proto, cont, dest, ou}
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand All @@ -1887,7 +1884,7 @@ defmodule Lua.VM.Dispatcher do

{:lua_closure, _, _} = closure ->
args = collect_args(regs, base + 1, total_args)
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -2452,7 +2449,7 @@ defmodule Lua.VM.Dispatcher do
{:lua_closure, _, _} = closure,
args,
name_hint,
_line,
line,
code,
pc,
regs,
Expand All @@ -2466,7 +2463,7 @@ defmodule Lua.VM.Dispatcher do
cd,
ou
) do
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down Expand Up @@ -2513,7 +2510,7 @@ defmodule Lua.VM.Dispatcher do
args,
base,
name_hint,
_line,
line,
code,
pc,
regs,
Expand All @@ -2527,7 +2524,7 @@ defmodule Lua.VM.Dispatcher do
cd,
ou
) do
call_info = {proto.source, 0, name_hint}
call_info = {proto.source, line, name_hint}
instruction_count = tick(state, instruction_count, cs, cd)
ckdepth(state, cs, cd)

Expand Down
21 changes: 16 additions & 5 deletions lib/lua/vm/stdlib.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -189,12 +189,13 @@ defmodule Lua.VM.Stdlib do
# Per Lua 5.3 §6.1 the raised value passes through pcall/xpcall verbatim,
# and string messages gain a `source:line:` prefix unless `level == 0`.
# The prefixed view lives in `:lua_value` (Lua-facing only); `:value`
# stays raw so host rendering is untouched. Levels >= 2 (attribute to the
# caller's caller) need per-frame lines the call stack does not carry and
# are treated as level 1 for now.
# stays raw so host rendering is untouched. Level 2 names the line the
# erroring function was called from, level 3 its caller's, and so on: each
# call-stack frame records its call site. A level past the stack omits the
# prefix, as PUC Lua does.
defp lua_error([message | rest], state) do
{line, source} = Executor.current_position()
level = error_level(rest)
{line, source} = error_position(level, state)

raise RuntimeError,
value: message,
Expand All @@ -209,9 +210,19 @@ defmodule Lua.VM.Stdlib do
raise RuntimeError, value: nil, line: line, source: source, state: state
end

defp error_level([level | _]) when is_number(level), do: level
defp error_level([level | _]) when is_integer(level), do: level
defp error_level([level | _]) when is_float(level), do: trunc(level)
defp error_level(_), do: 1

defp error_position(level, state) when level >= 2 do
case Enum.at(state.call_stack, level - 2) do
{source, line, _name} when is_integer(line) and line > 0 -> {line, source}
_ -> {nil, nil}
end
end

defp error_position(_level, _state), do: Executor.current_position()

# §6.1 position prefix: only string messages, only when `level ~= 0`, and
# only when the executor recorded a usable position. A `{nil, _}` position
# (native call inside a compiled closure — the dispatcher does not plumb
Expand Down
18 changes: 9 additions & 9 deletions test/lua/error_gallery_test.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,16 +121,16 @@ defmodule Lua.ErrorGalleryTest do
Lua runtime error: runtime error: stack overflow

Stack trace:
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
... 20 more frames ...
gallery.lua:0: in function 'f'
gallery.lua:0: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:1: in function 'f'
gallery.lua:2: in function 'f'\
"""}
]
Expand Down
39 changes: 39 additions & 0 deletions test/lua/vm/pcall_error_value_test.exs
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Original file line number Diff line number Diff line change
Expand Up @@ -203,6 +203,45 @@ defmodule Lua.VM.PcallErrorValueTest do

assert results == [false, "hi"]
end

test "level 2 blames the caller's line" do
{results, _state} =
run(
"""
local function check(x)
if not x then error("bad input", 2) end
end
local ok, err = pcall(function()
check(false)
end)
return err
""",
@engine
)

assert results == ["test.lua:5: bad input"]
end

test "level 3 blames the caller's caller" do
{results, _state} =
run(
"""
local function check(x)
if not x then error("deep", 3) end
end
local function validate(x)
check(x)
end
local ok, err = pcall(function()
validate(false)
end)
return err
""",
@engine
)

assert results == ["test.lua:8: deep"]
end
end

describe "xpcall hands the raw value to the handler (#{engine} engine)" do
Expand Down