File size: 3,560 Bytes
7e9dc27 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 | --- A template preprocessor.
-- Originally by [Ricki Lake](http://lua-users.org/wiki/SlightlyLessSimpleLuaPreprocessor)
--
-- There are two rules:
--
-- * lines starting with # are Lua
-- * otherwise, `$(expr)` is the result of evaluating `expr`
--
-- Example:
--
-- # for i = 1,3 do
-- $(i) Hello, Word!
-- # end
-- ===>
-- 1 Hello, Word!
-- 2 Hello, Word!
-- 3 Hello, Word!
--
-- Other escape characters can be used, when the defaults conflict
-- with the output language.
--
-- > for _,n in pairs{'one','two','three'} do
-- static int l_${n} (luaState *state);
-- > end
--
-- See @{03-strings.md.Another_Style_of_Template|the Guide}.
--
-- Dependencies: `pl.utils`
-- @module pl.template
local utils = require 'pl.utils'
local append,format,strsub,strfind = table.insert,string.format,string.sub,string.find
-- If expression nesting is too deep, loading will result in
-- "chunk has too many syntax levels " error.
-- By default the limit is 200, but it can be also consumed by nested blocks
-- added in raw Lua code, so it's better to stop earlier.
local max_concatenations = 100
local function parseDollarParen(pieces, chunk, exec_pat)
local concatenations = 0
local s = 1
for term, executed, e in chunk:gmatch(exec_pat) do
executed = '('..strsub(executed,2,-2)..')'
concatenations = concatenations + 2
if concatenations > max_concatenations then
append(pieces, format("%q)_put((%s or '')..",
strsub(chunk,s, term - 1), executed))
concatenations = 1
else
append(pieces, format("%q..(%s or '')..",
strsub(chunk,s, term - 1), executed))
end
s = e
end
append(pieces, format("%q", strsub(chunk,s)))
end
local function parseHashLines(chunk,brackets,esc)
local exec_pat = "()$(%b"..brackets..")()"
local esc_pat = esc.."+([^\n]*\n?)"
local esc_pat1, esc_pat2 = "^"..esc_pat, "\n"..esc_pat
local pieces, s = {"return function(_put) ", n = 1}, 1
while true do
local ss, e, lua = strfind(chunk,esc_pat1, s)
if not e then
ss, e, lua = strfind(chunk,esc_pat2, s)
append(pieces, "_put(")
parseDollarParen(pieces, strsub(chunk,s, ss), exec_pat)
append(pieces, ")")
if not e then break end
end
append(pieces, lua)
s = e + 1
end
append(pieces, " end")
return table.concat(pieces)
end
local template = {}
--- expand the template using the specified environment.
-- There are three special fields in the environment table `env`
--
-- * `_parent` continue looking up in this table (e.g. `_parent=_G`)
-- * `_brackets`; default is '()', can be any suitable bracket pair
-- * `_escape`; default is '#'
--
-- @string str the template string
-- @tab[opt] env the environment
function template.substitute(str,env)
env = env or {}
if rawget(env,"_parent") then
setmetatable(env,{__index = env._parent})
end
local brackets = rawget(env,"_brackets") or '()'
local escape = rawget(env,"_escape") or '#'
local code = parseHashLines(str,brackets,escape)
local fn,err = utils.load(code,'TMP','t',env)
if not fn then return nil,err end
fn = fn()
local out = {}
local res,err = xpcall(function() fn(function(s)
out[#out+1] = s
end) end,debug.traceback)
if not res then
if env._debug then print(code) end
return nil,err
end
return table.concat(out)
end
return template
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