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pretty/function.lua

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--[=[ The function formatting module for pretty.
How is one supposed to pretty print functions? Well, there are many different
formats, and no "best" one, only "best for the purpose". Lets start at the
simplest, and move towards abstraction.
1. The default Lua format: "function: 0x41f71c60"
This is the default, and by far the easiest. Also, very uninformative. We
only get a unique id for the function.
2. Include the arguments: "function (t, str) ... end"
This is slightly more advanced, as it requires using the debug library to
discover the names of the arguments. In addition it comes closer to a Lua
parsable formatting. We can know the argument names, and if these are
descriptive, we can learn some things about the function.
3. Include some documentation: "function (x) --[[math.cosh: Returns the hyperbolic cosine of x.]] ... end"
We retain the arguments and almost parsable formatting from above, and add
documentation taken from elsewhere - Lua Reference Manual, LuaJIT webpage -
as comments. This is great for explorative programming, as we can read about
the language by just fiddling around with it.
4. Short names: "math.min"
We can assume that an experienced Lua user might already know how any given
library function works, and would thus prefer a shorthand, rather than the
documentation. To that aim, we can use the short name/access path instead.
This is also ideal in places where we don't have a lot of space.
This representation is completely parsable, but won't necessarily work for
custom enviroment and user-defined functions.
5. Include source code: "function (a, b) return (a + b)/2 end"
Now we find the source code somehow, and use it as the representation. This
is powerful because we can directly inspect the code. But it makes the
function representation a lot more bussy. It won't work with builtins,
closured functions, or when fucking around with the source files. It also
hits limits when functions are nested, as the debug library does not give
enough precision.
This also works nicely with 3. due to being able to read function
documentation from the source file.
6. Include closures: "(function () local i = 5; return function () i = i + 1; return i end end)()"
In cases where a function has a closure, we can use debug.getinfo to get
the names and values of the upvalues. We can then represent the closure, by
creating the closure itself. Iterators like the example above works nicely,
but more complex chains of closures break down. For example:
local val_a = 1
local func_a = function () val_a = val_a + 1; return val_a end
local val_a = val_a
local func_c = function () return func_a() + val_a end
Here we have two functions, both with their own upvalue, both named "val_a",
yet those names refer to two different "slots". Successive calls to
`func_c` should produce the list: 2, 3, 4, 5, 6, 7, ...
To break through this barrier, we need to parse the Lua AST, and that is
beyond this project.
Closures also create extremely bussy output.
--]=]
-- Import
local LIBRARY
do
local thispath = ... and select('1', ...):match('.+%.') or ''
local was_loaded, library = pcall(require, thispath..'library')
LIBRARY = was_loaded and library or {}
end
-- Constants
-- FUNCTION_DEFINITION_MATCH is a lua pattern, for finding a function definition.
-- NOTE: It will match malformed unicode sequences, and thus assumes that the
-- string checked against have been checked by the lua interpreter.
local FUNCTION_KEYWORD_MATCH = '%f[%a_]function%f[^%a_]'
local FUNCTION_DEFINITION_MATCH = '.-' .. -- Look for stuff before the function
FUNCTION_KEYWORD_MATCH .. '%s*' .. -- Look for the function keyword
'([a-zA-Z0-9\128-\255_.:]*)%s*' .. -- Look for the function name, if any
'(%([a-zA-Z0-9\128-\255_,. \t]*%))' .. -- Look for the function parameter list.
'[ \t]*(.+)[ \t]*' .. -- Look for the function body
'end' -- Look for the end keyword
local NR_CHARS_IN_LONG_FUNCTION_BODY = 30
--------------------------------------------------------------------------------
-- Util
local function get_function_info (f)
-- NOTE: Works best in LuaJIT or Lua 5.2+
-- Regarding get-info:
-- * No need to includ 'f'. Function is already known
-- * No need to include 'L' (active lines) option. Ignored
-- * No need to include 'n' (name and namewhat). Won't work.
assert(type(f) == 'function')
local info = debug.getinfo(f, 'Su')
info.params = {}
info.ups = {}
info.env = debug.getfenv and debug.getfenv(f)
info.builtin = (info.source == '=[C]')
for i = 1, info.nparams or 0 do info.params[i] = debug.getlocal(f, i) end
if info.isvararg or not info.nparams then info.params[#info.params+1] = '...' end
-- Get upvalues
for i = 1, info.nups do
local k, v = debug.getupvalue(f, i)
if k == '_ENV' and not debug.getfenv then
info.env = v
else
info.ups[k] = v
end
end
if info.source:sub(1,1) == '=' then info.defined_how = 'C'
elseif info.source:sub(1,1) == '@' then info.defined_how = 'file'
elseif info.source:find'^%w+.lua$' then info.defined_how = 'file' -- XXX: Hotfix for Love2d boot.lua issue.
else info.defined_how = 'string'
end
if info.builtin and LIBRARY[f] then
info.name = LIBRARY[f].name
info.params[1] = LIBRARY[f].para
info.docs = LIBRARY[f].docs
end
return info
end
local function get_line_index (str, line_nr)
assert(type(str) == 'string')
assert(type(line_nr) == 'number')
local index = 0
for _ = 2, line_nr do
index = str:find('\n', index, true)
if not index then return #str end
index = index + 1
end
return index
end
local function get_docs_from_function_body (body, max_index)
-- Finds the documentation lines of a function.
-- Also returns the remaining non-documentation lines.
assert(type(body) == 'string')
local doc_lines = {}
for line in body:sub(1, max_index):gmatch('[^\n]+', true) do
if not line:match '^%s*$' then
local line_text = line:match '^%s*%-%-%s*(.*)%s*$'
doc_lines[#doc_lines+1] = line_text
if not line_text then break end
end
end
return table.concat(doc_lines, '\n'):match '^%s*(.-)%s*$'
end
local function get_docs_split_index (body)
local index = 1
while index <= #body do
local next_newline = body:find('\n', index + 1) or -1
if body:sub(index, next_newline):match('^%s*$') or body:sub(index, next_newline):match('^%s*%-%-%s*(.*)%s*$') then
index = next_newline
else
return index
end
end
return -1
end
local function get_function_body_info (info)
-- Will attempt to expand `info` with extra info found by looking at the
-- source code. This could require opening a file.
-- There is no guarentee that the function body it finds is correct, or even
-- that it finds any.
-- Error check
assert(type(info) == 'table')
if info.defined_how == 'C' then
error('[pretty.function/internal]: Cannot find source-code for C functions.', 2)
end
-- First find the string to search through.
local str = info.source
if info.defined_how == 'file' then
-- Read file
local file = io.open(info.short_src, 'r')
if file then
str = file:read '*all'
file:close()
else
str = nil
end
end
if not str then return info end
-- Calculate indices of the lines the function should be defined at.
local start_line_index = get_line_index(str, info.linedefined)
local end_line_index = get_line_index(str, info.lastlinedefined + 1)
-- Now find some info about the function.
-- NOTE: function_params is currently not used for anything.
local function_name, function_params, function_body = str:sub(start_line_index, end_line_index):match(FUNCTION_DEFINITION_MATCH)
if type(function_body) ~= 'string' then
error(('[pretty.function/internal]: Could not find the function defined on lines %i-%i (indices %i-%i) for string:\n\n%s\n'):format(info.linedefined, info.lastlinedefined, start_line_index, end_line_index, str))
end
local function_body = function_body:match '^%s*(.-)%s*$'
local pivot_index = get_docs_split_index (function_body)
info.name = info.name or function_name:match '^%s*(.-)%s*$'
info.docs = info.docs or get_docs_from_function_body(function_body, pivot_index)
info.body = info.body or function_body:sub(pivot_index, -1):match '^%s*(.-)%s*$'
if info.name == '' then info.name = nil end
if info.docs == '' then info.docs = nil end
return info
end
--------------------------------------------------------------------------------
-- Text handling
local function width_of_strings_in_l (l, start_i, end_i)
-- FIXME: Copy of the one in pretty.lua
local width = 0
for i = start_i or 1, (end_i or #l) do
width = width + #l[i]
end
return width
end
local function add_indent_to_string (str, indent)
assert(type(str) == 'string')
assert(type(indent) == 'string')
return indent .. str:gsub('\n', '\n'..indent)
end
local function wrap_text (text, max_width)
local l, i, last_i = {}, max_width, 1
repeat
if text:sub(i, i) == ' ' then
l[#l+1], last_i, i = text:sub(last_i, i - 1), i + 1, i + max_width
elseif i <= last_i then
-- TODO: Make sure this part works.
i = text:find(' ', last_i) or #text
else
i = i - 1
end
until i >= #text
l[#l+1] = text:sub(last_i)
return table.concat(l, '\n')
end
--------------------------------------------------------------------------------
return function (value, depth, l, format_value)
assert(type(value) == 'function')
assert(type(depth) == 'number' and type(l) == 'table' and type(format_value) == 'function')
local info = get_function_info(value)
local function_params, function_body = nil, '...'
if not info.docs and info.defined_how ~= 'C' then
info = get_function_body_info(info)
if info.body and #info.body <= NR_CHARS_IN_LONG_FUNCTION_BODY and not info.body:find '\n' and not info.body:find(FUNCTION_KEYWORD_MATCH) then
if info.defined_how == 'string' then function_body = info.body end
end
end
if info.builtin and l.options.short_builtins then
assert(info.name)
return l(info.name);
end
-- Include function modifier, and alignment info.
l[#l+1] = info.builtin and 'builtin ' or ''
l[#l+1] = { 'align', 'func_mod', #l[#l]}
-- Build rest of function signature
l[#l+1] = 'function '
local top_before = #l
if function_params then
l[#l+1] = function_params
else
l[#l+1] = '('
for _, param in ipairs(info.params) do l[#l+1], l[#l+2] = param, ', ' end
if l[#l] == ', ' then l[#l] = nil end
l[#l+1] = ')'
end
l[#l+1] = { 'align', 'func_def', width_of_strings_in_l(l, top_before) }
-- Cleanup and finish
if depth ~= 0 then
l[#l+1] = (function_body:sub(1,1) == '\n') and '' or ' '
l[#l+1] = function_body
l[#l+1] = { 'align', 'func_end', #function_body }
l[#l+1] = (function_body:sub(-1) == '\n' or function_body == '') and '' or ' '
return l 'end'
end
-- More info! --
local indent = '\n' .. l.options.indent
-- Name
if info.name then
l[#l+1] = indent
l[#l+1] = '-- '
l[#l+1] = info.name
end
-- Doc
if info.docs then
l[#l+1] = '\n'
local indent = l.options.indent .. '-- '
local docs = not info.builtin and info.docs or wrap_text(info.docs, 80 - #indent)
l[#l+1] = add_indent_to_string(docs, indent)
end
-- source
if info.docs or info.name then -- Do nothing
elseif info.defined_how == 'string' then
l[#l+1] = indent
l[#l+1] = '-- Loaded from string'
elseif not info.builtin then
l[#l+1] = indent
l[#l+1] = ('-- Source file: \'%s\' '):format(info.short_src)
if info.linedefined == info.lastlinedefined then
l[#l+1] = ('[Line: %i]'):format(info.linedefined)
else
l[#l+1] = ('[Lines: %i - %i]'):format(info.linedefined, info.lastlinedefined)
end
end
-- upvalues
if info.nups > 0 and (not info.builtin and not info.docs) then
l[#l+1] = indent
l[#l+1] = '-- Up values: '
format_value(info.ups, depth + 1, l)
end
-- Ignore spacing and function body if it's a Λ string.
if function_body ~= '' then
l[#l+1] = '\n'
l[#l+1] = indent
l[#l+1] = function_body
end
l[#l+1] = '\nend'
end
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