lua-compat-env

lua-compat-env copied to clipboard

NAME

compat_env v$(_VERSION) - Lua 5.1/5.2 environment compatibility functions

SYNOPSIS

-- Get load/loadfile compatibility functions only if using 5.1. local CE = pcall(load, '') and _G or require 'compat_env' local load = CE.load local loadfile = CE.loadfile

-- The following now works in both Lua 5.1 and 5.2: assert(load('return 2*pi', nil, 't', {pi=math.pi}))() assert(loadfile('ex.lua', 't', {print=print}))()

-- Get getfenv/setfenv compatibility functions only if using 5.2. local getfenv = _G.getfenv or require 'compat_env'.getfenv local setfenv = _G.setfenv or require 'compat_env'.setfenv local function f() return x end setfenv(f, {x=2}) print(x, getfenv(f).x) --> 2, 2

DESCRIPTION

This module provides Lua 5.1/5.2 environment related compatibility functions. This includes implementations of Lua 5.2 style load and loadfile for use in Lua 5.1. It also includes Lua 5.1 style getfenv and setfenv for use in Lua 5.2.

API

local CE = require 'compat_env'

CE.load (ld [, source [, mode [, env] ] ]) --> f [, err]

This behaves the same as the Lua 5.2 `load` in both
Lua 5.1 and 5.2.
http://www.lua.org/manual/5.2/manual.html#pdf-load

CE.loadfile ([filename [, mode [, env] ] ]) --> f [, err]

This behaves the same as the Lua 5.2 `loadfile` in both
Lua 5.1 and 5.2.
http://www.lua.org/manual/5.2/manual.html#pdf-loadfile

CE.getfenv ([f]) --> t

This is identical to the Lua 5.1 `getfenv` in Lua 5.1.
This behaves similar to the Lua 5.1 `getfenv` in Lua 5.2.
When a global environment is to be returned, or when `f` is a
C function, this returns `_G`  since Lua 5.2 doesn't have
(thread) global and C function environments.  This will also
return `_G` if the Lua function `f` lacks an `_ENV`
upvalue, but it will raise an error if uncertain due to lack of
debug info.  It is not normally considered good design to use
this function; when possible, use `load` or `loadfile` instead.
http://www.lua.org/manual/5.1/manual.html#pdf-getfenv

CE.setfenv (f, t)

This is identical to the Lua 5.1 `setfenv` in Lua 5.1.
This behaves similar to the Lua 5.1 `setfenv` in Lua 5.2.
This will do nothing if `f` is a Lua function that
lacks an `_ENV` upvalue, but it will raise an error if uncertain
due to lack of debug info.  See also Design Notes below.
It is not normally considered good design to use
this function; when possible, use `load` or `loadfile` instead.
http://www.lua.org/manual/5.1/manual.html#pdf-setfenv

DESIGN NOTES

This module intends to provide robust and fairly complete reimplementations of the environment related Lua 5.1 and Lua 5.2 functions. No effort is made, however, to simulate rare or difficult to simulate features, such as thread environments, although this is liable to change in the future. Such 5.1 capabilities are discouraged and ideally removed from 5.1 code, thereby allowing your code to work in both 5.1 and 5.2.

In Lua 5.2, a setfenv(f, {}), where f lacks any upvalues, will be silently ignored since there is no _ENV in this function to write to, and the environment will have no effect inside the function anyway. However, this does mean that getfenv(setfenv(f, t)) does not necessarily equal t, which is incompatible with 5.1 code (a possible workaround would be [1]). If setfenv(f, {}) has an upvalue but no debug info, then this will raise an error to prevent inadvertently executing potentially untrusted code in the global environment.

It is not normally considered good design to use setfenv and getfenv (one reason they were removed in 5.2). When possible, consider replacing these with load or loadfile, which are more restrictive and have native implementations in 5.2.

This module might be merged into a more general Lua 5.1/5.2 compatibility library (e.g. a full reimplementation of Lua 5.2 _G). However, load/loadfile/getfenv/setfenv perhaps are among the more cumbersome functions not to have.

INSTALLATION

To install using LuaRocks:

luarocks install compat-env

Otherwise, download https://github.com/davidm/lua-compat-env.

You may simply copy compat_env.lua into your LUA_PATH.

Otherwise:

 make test
 make install  (or make install-local)  -- to install into LuaRocks
 make remove  (or make remove-local)  -- to remove from LuaRocks

Related work

http://lua-users.org/wiki/LuaVersionCompatibility https://github.com/stevedonovan/Penlight/blob/master/lua/pl/utils.lua - penlight implementations of getfenv/setfenv http://lua-users.org/lists/lua-l/2010-06/msg00313.html - initial getfenv/setfenv implementation

References

[1] http://lua-users.org/lists/lua-l/2010-06/msg00315.html

Copyright

(c) 2012 David Manura. Licensed under the same terms as Lua 5.1/5.2 (MIT license).

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.