Extension talk:Scribunto/Lua reference manual

capital in Then
Re : "If named arguments to #invoke are specified, for example " is not a full sentence, so "Then" cannot be with a capital.--Patrick1 (talk) 11:44, 30 August 2012 (UTC)

pattern in which function ?
"the empty capture captures the current string position (a number)." Perhaps a note about "pattern " could be usefull in these functions ? --Rical (talk) 11:51, 23 December 2012 (UTC)
 * string.find (s, pattern [, init [, plain]])
 * string.gmatch (s, pattern)
 * string.gsub (s, pattern, repl [, n])
 * string.match (s, pattern [, init])

What's available on WMF projects?
It seems like a lot of the libraries mentioned in this manual are not available on test2.WP, which I assume means that they won't be available on the WMF projects that Scribunto is about to be deployed on? (For example, mw.language, mw.site, mw.uri, and mw.ustring all appear to be missing.) Could this manual be edited to make clear which modules are available in what Scribunto versions? —Ruakh TALK 05:02, 18 February 2013 (UTC)
 * mw.ustring is available now. Here's a little test: User:Amire80/Scribunto. --Amir E. Aharoni (talk) 04:20, 19 February 2013 (UTC)
 * The hard part about that is idenfitying the versions. There isn't a 1:1 relationship between the version of MediaWiki and the version of Scribunto; for example, until the deploy 9 hours ago wmf9 had a relatively old version, which was upgraded to the newest. This could potentially be done again if warranted, rather than waiting for wmf11 to get the latest updates. Anomie (talk) 13:21, 19 February 2013 (UTC)
 * This is a point of confusion, though. As of right now there is no way to know for sure which functions are available on any given wiki, except by writing test code to see if it works or triggers a script error. At the very least, the documentation should specify the first Scribunto version for which each function became/will become available. CodeCat (talk) 22:19, 5 March 2013 (UTC)
 * Define "Scribunto version"; saying bit32 is first available in 5e548e769a464e3223cd52ffa0f819f6bf1c9924 doesn't help a whole lot. Anomie (talk) 02:34, 7 March 2013 (UTC)
 * It is possible to test existence of stuff by performing ~=nil tests. It is not very nice but it works (I use it in my test module to check functions that appears). Maybe we could write a "What's available module" that shows what is present or not? Hexasoft (talk) 08:59, 7 March 2013 (UTC)

(u)string patterns and PCRE
I believe, for people who know PCRE a special explanation of differences should be written, except that one must use  instead of  this will allow me, e.g., to do things like  or to create a table with some members, some of which may be functions, and construct new "instances" of this table by calling "new" and the table:

peace - קיפודנחש (talk) 18:07, 11 March 2013 (UTC)
 * The usual idiom seems to be to use  rather than  . Also, due to Scribunto's sandboxing, it is not possible for a  d library such as libraryUtils to add global functions as proposed here; it would wind up as , at which point you may as well use the normal idiom. BJorsch (WMF) (talk) 13:19, 12 March 2013 (UTC)
 * regarding your 2nd comment: sure, i meant  (also changed the snippets above to reflect this more correct usage). not a problem.
 * however, my Lua-fu is not that strong, and i'm not sure i understand your "standard idiom" comment. calling  result in an error, as well as  . if you mean i should write a new "new" function in any table i want to construct, then yes, i understand this is possible, but i think what i ask is both more elegant and simpler, while suplying the reuired functionality. of course, it won't stop anyone from creating tailored constructors, and calling them "new" or "construct" or duplicating the object name, or any other name they choose. peace - קיפודנחש (talk) 17:55, 12 March 2013 (UTC)

mw.text.unstrip
Hello, as far as I understand the doc, the  function will allow to "unstrip" incoming strings that include tags such as nowiki. It is fine (I filled the bugreport) because it will allow to read the full content of any kind of parameters. My question: does using  on the unstrip string will produce the same original string? Also, to be sure: unstrip will returns a copy, not modify the original string?

Regards, Hexasoft (talk) 19:31, 11 March 2013 (UTC)
 * No,  on the unstripped string will expand any wikitext in that string. Even if you were to add back the correct extension tag (e.g. wrap the string in , or , or whatever), the result still might not be the same. For example,   might return , but then unstripping might result in  : the HTML for the superscripted footnote, which isn't even valid for return from the Lua module since  is not allowed in wikitext. It's even possible that the text hidden behind   is something completely unexpected such as serialized PHP data, as it may be that the extension is intending to do postprocessing in a ParserAfterParse hook or the like.
 * Yes,  does not modify the original string. Strings in Lua are immutable and primitive values are passed by value, so it is not possible to modify an input string in a normal function call (you can modify the keys/values in an input table, of course). BJorsch (WMF) (talk) 13:38, 12 March 2013 (UTC)
 * Thanks for the clarification. I will play with it when available. Regards, Hexasoft (talk) 17:58, 12 March 2013 (UTC)

In section "mw.language:formatDate"
Hello, in section Extension:Scribunto/Lua reference manual it is said: « Formats a date according to the given format string. If  is omitted, the default is the current time. The value for  must be a boolean or nil; if true, the time is formatted in the server's local time rather than in UTC. » Rather than « server's local time » shouldn't it be « wiki local time »?

Regards, Hexasoft (talk) 16:39, 17 March 2013 (UTC)
 * Yes, it should be. Thanks for pointing out the error. BJorsch (WMF) (talk) 23:10, 17 March 2013 (UTC)
 * I just noticed some similar language in the os.date section. I assume this should also be wiki time, rather than server time? — Mr. Stradivarius  ♪ talk ♪ 10:52, 3 February 2014 (UTC)
 * os.date is a Lua builtin and really does use the server's local time. You can test this easily enough by going to dewiki or another wiki with a non-UTC local time set, edit any module page to get to the debug console, and compare the output of  versus  . Anomie (talk) 14:12, 3 February 2014 (UTC)

Suggestion for mw.text: word distance
Hello, I had the need of a distance function beetween words, and coded en:Levenshtein distance in my module. Don't know if it should be useful (I see few cases where that feature can be useful) but if you think it is it could have its place in mw.text module. Moreover I think it is the kind of algorithm that can be far more efficient in something else than Lua (I guess that a double-looping on characters from two strings is − for example − far more efficient in C or any language that gives direct accès to string elements).

Regards, Hexasoft (talk) 17:21, 21 March 2013 (UTC)
 * There are a lot of things that would be easier done in PHP, but on the other hand we don't want to bloat the Scribunto libraries with too many features that won't be of general use. On this one, I'd personally lean towards "no". But if someone else wants to code it up and put a patch in Gerrit, they can and we'll see what anyone else things. BJorsch (WMF) (talk) 13:28, 22 March 2013 (UTC)

environment for getfenv(function)

 * We can read : "Passing a function returns the environment that will be used when that function is called."
 * Can we say : "Passing a function returns the environment where this calling function is, if any, else nil. In case of recursive function, returns the nearest call of this function." ? --Rical (talk) 18:40, 21 March 2013 (UTC)
 * That would not be accurate. All functions have an environment, it's just that Scribunto may restrict access to some of them. And the environment returned depends on the function, not on the call stack; the "environment" returned is usually the same table that function sees as . BJorsch (WMF) (talk) 13:38, 22 March 2013 (UTC)

Conditionals
The reference doesn’t formally cover if-then-else conditionals. —Michael Z. 2013-03-21 21:55 z 
 * Extension:Scribunto/Lua reference manual seems to cover it. BJorsch (WMF) (talk) 13:39, 22 March 2013 (UTC)

mw.text.tag request
So there is one special property for tags, also known as "style". jQuery acknowledge this, so setting style elements is not done through calling elem.attr('style', something) (although this will also work), but rather, they provide a special api called elem.css.

so here is the request: to provide some mw.text.XXX support for style. this can be done either by augmenting the ma.text.tag somehow, or by creating a whole new mw.text.style(...). if the latter approach is taken, i'd like to make a suggestion: please allow for multiple parameters, and concatenate them using semicolon. so the call should look something like so: this is not meant to be the code itself, necessarily - clearly i did not think of all the possible implications. it's more of a sektch to illustrate the required functionality of helping the lua programmers composing "style" attribute from different bits and pieces of flotsam. either way, some functionality that would best mimic jQuery's ".css" would be greatly appreciated. peace - קיפודנחש (talk) 15:40, 30 March 2013 (UTC)

Fragment
The arguments for  are. Namespace, title, and interwiki are familiar enough to me, but what does fragment mean? Does this refer to the project link? I assume, for example, that the "fragment" in  would be "wikt". Is this correct? — Mr. Stradivarius  ♪ talk ♪ 11:19, 3 April 2013 (UTC)
 * Ah, I see I was wrong after playing around with this for a bit. It seems the fragment is the part that appears after "#" in the URL, and that the "interwiki" part includes both the project name and the language name. If no-one has any objections, I think I'll update the manual to say this. — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 12:32, 3 April 2013 (UTC)
 * Feel free. Note that "fragment" (or sometimes "fragment identifier") is the actual name for that part of a URL, see RFC 3986 § 3.5. Anomie (talk) 13:37, 3 April 2013 (UTC)

Access to MediaWiki API; access to page text
Hi. I have two somewhat related questions.


 * 1) Is there any ability currently to access the MediaWiki API from Scribunto? For example, I'd like to get a list of all the subpages of Global message delivery/Targets. This is available in the MediaWiki API, but I'm not sure if Scribunto can retrieve this information right now. It'd be super-helpful to have a Special:PrefixIndex equivalent available (or more generally, access to the MediaWiki API).
 * 2) Is there any ability currently to access page text? For example, I want to count instances of a string within the wikitext of Global message delivery/Targets/Wikidata.

Thanks in advance for any help or pointers here. --MZMcBride (talk) 18:03, 4 April 2013 (UTC)
 * Hello,
 * I can answer to the #2 question: title objects has a getContent method, allowing to get the raw content of the page corresponding the the title object. See Extension:Scribunto/Lua_reference_manual (the last entry). It think it is what you are looking for. Regards, Hexasoft (talk) 19:18, 4 April 2013 (UTC)
 * PS: note that I read somewhere that a Scribunto library exists (or is planed) to access wikidata stuff. Not sure about how advanced it is.
 * note that title object in general, and getContent in particular, do not work for titles on another wiki/site, so if the requirement is, for instance, to get the content of Global message delivery/Targets/Wikidata from any other wiki than meta, it won't help you, and i do not think this is possible. peace - קיפודנחש (talk) 22:37, 4 April 2013 (UTC)
 * The Wikibase Lua API will be deployed as the same time as the #property parser function. So, next Monday for en Wikipedia and, if all is good, Wednesday for the others. Here is the doc. I've already written [//test2.wikipedia.org/wiki/Module:Wikidata a module to test it]. Tpt (talk) 20:05, 5 April 2013 (UTC)
 * Making arbitrary API queries from Scribunto is probably not going to happen; they would be slow and prone to issues with proper data sanitization and accounting of the CPU time. This was discussed in this wikitech-l thread. BJorsch (WMF) (talk) 13:30, 5 April 2013 (UTC)
 * All right. So for the Special:PrefixIndex example mentioned above, how would I achieve this functionality? File a bug in Bugzilla about adding this functionality to Lua/Scribunto? Will I need to do this for each MediaWiki API feature I want ported over to Scribunto/Lua? (Generating input lists seems like it'll be a pretty commonly needed functionality inside Scribunto modules, to avoid duplicating/hardcoding lists of pages, templates, transclusions, categories, images, external links, etc.) --MZMcBride (talk) 18:33, 7 April 2013 (UTC)

Links related to this discussion:


 * wmf:Module:Count
 * m:Module:Count
 * 47137

Perhaps these will be helpful to someone. --MZMcBride (talk) 20:48, 11 April 2013 (UTC)


 * Actually, you can transclude and unstrip Special:PrefixIndex - see w:Module:Module overview for an example. A problem though is that I found out this causes the cache to be disabled, so the page is regenerated on every view.  On the other hand, you can use the mw.message library to link to the such an uncacheable page, and then the page will never be updated except when it is edited.  Alas, I still know of no way to say refresh the cache once a day or once a week.  (Speaking of which I never did remember to update Module Overview to avoid reloads, hmmm... Wnt (talk) 05:54, 24 January 2014 (UTC)
 * And only limited number of subpages is processed. See also category handling by Lua: ru:module:category. Ignatus (talk) 16:00, 24 January 2014 (UTC)

System messages with "page" or "subpage" ?
Hi.

Do you know what's the diffrence between messages system like Mediawiki:Scribunto-doc-subpage-xxx and Mediawiki:Scribunto-doc-page-xxx ? It seems that the twice exist.

Thanks by advance for your answer, Automatik (talk) 14:53, 5 April 2013 (UTC)
 * "Mediawiki:Scribunto-doc-subpage-xxx" was renamed to "Mediawiki:Scribunto-doc-page-xxx". The former is no longer used. BJorsch (WMF) (talk) 21:16, 6 April 2013 (UTC)
 * Thanks! Automatik (talk) 00:55, 7 April 2013 (UTC)

Extension for mw.text.listToText
Hello, it may be usefull to add the possibility to add something before/after items given to. I.e. something like ... or why not ... so that it would not need to preprocess incoming parameters just to add constant strings before/after them before passing them to.

Maybe something like an optional  parameter (i.e. " %s ", or optional pre and post parameters).

Regards, Hexasoft (talk) 21:50, 6 April 2013 (UTC)
 * Hmmm… Well, in fact it can be simulated by:
 * . The only problem is that it prevent using the default separators. Regards, Hexasoft (talk) 08:55, 9 April 2013 (UTC)
 * Yes, I also would like to use %1..9 in the string formats, example:  like in , with a last string format for the last element, and another string format for all other before elements. --Rical (talk) 11:09, 9 April 2013 (UTC)

mw.language:parseFormattedNumber
Documentation says:

This takes a number as formatted by lang:formatNum and returns the actual number. In other words, this is basically a language-aware version of.

However, if you call, you will not get nil as expected (after all, this is what tonumber returns), but rather 'bla bla bla'. i'd rather you fix the code to do what the documentation implies rather than fix the documentation to say what the code currently does, so i did not touch the documentation. however, i recommend that until this is fixed, we should use  if we really wand "tonumber" behavior. peace - קיפודנחש (talk) 17:25, 12 April 2013 (UTC)
 * Anomie (talk) 00:56, 16 April 2013 (UTC)

File information
Is it possible to add file dimensions to the title objects? Is this even the right place to ask? — 69.162.8.80 17:47, 12 April 2013 (UTC)
 * Better would be bugzilla. Anomie (talk) 00:43, 16 April 2013 (UTC)

Debug console
Hi,

When we edit a module, we can see below the interface edition the debug console where it's written:

«* Precede a line with "=" to evaluate it as an expression, or use print.»

But the function print is not available. How to change this text (in all languages)?

Thanks by advance, Automatik (talk) 21:01, 14 April 2013 (UTC)
 * It works fine for me. Something like  prints whatever the   function returns, same as   does.   doesn't do anything in the module itself, but you can use it in the debug console—at least on en.wikipedia. — 69.162.8.80 20:32, 15 April 2013 (UTC)
 * Yes,  is available as an alias for   in the console only. See Extension:Scribunto/Lua reference manual. Anomie (talk) 00:41, 16 April 2013 (UTC)
 * it would be nice if we had the debug console in Special:TemplateSandbox, to get the output of all the modules. is it possible to expand the synergy between Extension:Scribunto and Extension:TemplateSandbox as to include scribunto debug console in the sandbox? it would be nice, of course, to do it in the most generic way possible, so if sandbox will learn to do its thing with other extensions, they will be able to hook *their* debug console to the sandbox too. peace - קיפודנחש (talk) 22:02, 19 April 2013 (UTC)
 * I've been working on including the mw.log output in all page previews. But it's currently hung up on a tangential UI change that I haven't had time to get to. BJorsch (WMF) (talk) 12:58, 22 April 2013 (UTC)
 * Thanks. i think it will be very useful. peace - קיפודנחש (talk) 21:52, 22 April 2013 (UTC)

argument to
What does it do? Seems like nothing, in console  gives the opened module name, not "Ignatus". Well, it would be great if someday we could expand templates like on a page with specific title. Ignatus (talk) 08:17, 16 April 2013 (UTC)
 * It sets the title of the new frame. But at a glance, I don't see anything that actually uses the frame's title ( gets the title of the page being parsed from the parser). Anomie (talk) 12:48, 16 April 2013 (UTC)

mw.text.unstrip: be able to detect wiki tag?
Hello, the  will be useful for some cases where we get parameters in nowiki tag is some cases. But is there a way to know that a string is "tagged" and/or to know with which tag(s)? Of course comparing str with unstrip(str) can do it for the first point but it is not very nice, and it don't allow to know which kind of data is inside (I mean, nowiki or pre should be fine 'cause data inside is « real », ref is probably not fine − <a href="#_note-toto-1">[1]</a> is not treatable).

Regards, Hexasoft (talk) 13:34, 30 April 2013 (UTC)
 * You can extract the tags that  replaces with a pattern something like  . Often a pattern like   should give you the name of the tag too, but that's not guaranteed to work. Anomie (talk) 13:00, 1 May 2013 (UTC)
 * Yes. When I played with stripped strings I found this point. As internal strip structure is internal maybe a mw.text.isStripped(text) that whould return nil or a string with the tag found? (or to make unstrip returning a second argument with the same convention?)
 * It is clearly not difficult to code this by myself. It would be useful if the internal structure may change in the future. If not it is not an important point.
 * Thanks, Hexasoft (talk) 08:33, 22 May 2013 (UTC)

mw.ustring.isutf8
Hi,

Is it normal that I get  ? How to understand what a utf8 character is?

Thanks by advance, Automatik (talk) 01:56, 2 May 2013 (UTC)
 * Yes, because that string is valid UTF-8. You would get false for something like  because a byte 128 may not follow a byte 48 in a UTF-8-encoded string. See UTF-8 (or, as I see you edit most on French-langauge projects, UTF-8) for details on UTF-8 encoding. Anomie (talk) 13:15, 2 May 2013 (UTC)

metamethod
Is it planned to use it for overriding # operator? I see it is highlighted in edit window like others but doesn't yet work. Ignatus (talk) 11:41, 16 May 2013 (UTC)
 * The __len metamethod does not apply to tables in Lua 5.1, which Scribunto is based on. If there is a way to simulate it in pure Lua 5.1 (i.e. without recompiling or loading C libraries), we'd be very interested. Anomie (talk) 13:27, 16 May 2013 (UTC)
 * It is possible to get that behaviour using proxies. It is possible to create a light userdata with, whose   metamethod is called when the   operator is used. Example:


 * A safe version of  could be provided: check that you're not setting the metatable of a core object, like strings, numbers, booleans or nil.


 * ... but Scribunto backports __pairs and __ipairs from Lua 5.2.. Why isn't __len for tables supported as well? I don't think it it would break any existing code, since  is currently useless if you don't want the default behavior. -- Pygy 81.243.36.191 11:55, 3 June 2013 (UTC)
 * Hmm, undocumented, which seems to have been removed entirely in 5.2. I'll have to have a look at that at some point, to see if it seems close enough to a real table to be usable internally (e.g. for  ).   may turn out to be troublesome. But at a glance I doubt we'll want to expose   and even a wrapped   to module code.
 * We can backport __pairs and __ipairs because doing in in pure Lua just requires redefining pairs and ipairs using documented and supported methods; see . Anomie (talk) 14:38, 3 June 2013 (UTC)
 * was experimental and it was removed because its primary use case (the custom  metamethod) was no longer needed in 5.2.   returns  . The  patch that backports len is rather short (https://github.com/dubiousjim/luafiveq/blob/master/patches/table-len.patch)... Why are you reluctant to use a patched version? BTW, if you are using LuaJIT, enabling   is one compile-time switch away. Edit: my bad regarding LuaJIT: the flag I mentioned also enable a slew of other Lua 5.2 features, and removes two methods from the standard lib... That being said, the functionality is already there, it must just be enabled. -- Pygy 81.243.36.191 22:46, 3 June 2013 (UTC)
 * Because we want other wikis to be able to use Scribunto without installing custom binaries, which their hosting provider may not even allow. At one time even requiring the stock Lua interpreter was worrisome. Anomie (talk) 13:51, 5 June 2013 (UTC)
 * That makes sense, I'm not familiar with the distribution process of MediaWiki. If I understand you properly, providing patched Lua source and binaries along with MediaWiki is not an option, then... -- Pygy 89.90.144.90 08:50, 10 June 2013 (UTC)
 * It turns out that debug.setmetatable is not needed:


 * -- Pygy

Please tell something more about frame:getParent
frame:getParent Called on the frame created by, returns the frame for the page that called. Called on that frame, returns nil.

Very exoteric doc.... :-D  I couldn't understand what it means; but, while browsing some script into fr.source, I found (if I'm not wrong) that this is the key to pass arguments from a template to a Lua script, and this is mostly important (see s:fr:Module:Table. Can someone expand doc as it deserves? Thanks! --Alex brollo (talk) 07:59, 23 May 2013 (UTC)
 * Hello,
 * the frame is the "environment" of the caller. This environment (mainly) includes the agurments given to the call (the #invoke). As modules are often called from a template, which is used in articles, the arguments given to the template are not in the frame but in the getParent of the frame. Let give an example:
 * In article foo we call . This template do:.
 * In the function myfunction from module Module:Mymodule if you read the arguments in  you will find modulearg1 and modulearg2 as unamed arguments. If you access the args table of the parent frame (using  ) you will find templatearg1 and templatearg2 as unamed arguments.
 * Of course if you directly use a module with #invoke rather than with an intermediate template only the main frame exists.
 * Hope it will help you.
 * Regards, Hexasoft (talk) 08:20, 23 May 2013 (UTC)
 * Thanks! I'll test into my sandbox. I guess, from fr.source script, that I can retrieve templatearg1 and templatearg2 by   even if template doesn't pass parameters explicitely when calling the module (a statement   is sufficient). Well, I've what I need to learn by "try and learn". --Alex brollo (talk) 10:03, 23 May 2013 (UTC)
 * It runs :-) --Alex brollo (talk) 13:18, 23 May 2013 (UTC)

mw.language:formatNum in the Lithuanian
In the Lithuanian number 123456.78 must be given as "123 456,78". but result is "123&#nbsp;456,78". --Vpovilaitis (talk) 05:09, 24 May 2013 (UTC)
 * It works fine for me:  returns "123 456,78", with a raw non-breaking space character. Whatever you're using to encode html entities appears to be mis-encoding the non-breaking space as "&amp;#nbsp;" rather than "&amp;nbsp;". Anomie (talk) 07:17, 24 May 2013 (UTC)
 * Thanks. I'm experiment with en:Module:Chart. But this text was in tooltip (title tag). --Vpovilaitis (talk) 08:03, 24 May 2013 (UTC)

I'm lazy, so I'm going to suggest...
Could there be another set of classes added: Just an idea to enable my laziness... :p Technical 13 (talk) 17:08, 7 June 2013 (UTC)
 *  : represents all magic characters.
 *  : All characters not in.
 * Not likely. We don't want to mess around with extending the standard Lua methods like, and we don't want to take the   methods too far from the corresponding   methods.
 * Also, what would be the point of this? The only thing I can see that it might be useful for is if you were trying to escape a user-supplied value-that's-not-supposed-to-be-a-pattern, but for that you can just use  because all magic characters are in %p and anything in %p that isn't magic will still work properly when escaped. Anomie (talk) 15:08, 8 June 2013 (UTC)

String methods
The manual says that when we call a method on a string, we are using the string library. So in the above code, we would be calling the function. However, it also says that using the string library cannot operate on unicode characters, and that we should use the mw.ustring library instead. For this reason, is using string methods a bad idea? I have noticed a few places that they are used in code already, and I am curious. — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 08:51, 12 June 2013 (UTC)
 * Personally, I try to avoid it in Scribunto code for that reason. Although if you are doing bytestring manipulation, the ability to chain calls is useful. But IMO that's a matter for a style guide rather than the reference manual. Anomie (talk) 12:59, 12 June 2013 (UTC)
 * That's what I thought - thanks for the clarification. I guess I'm new to issues of coding style - such things didn't really exist (?) with template code. — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 12:18, 20 June 2013 (UTC)

mw.ustring library missing reverse method
this may seem as a useless method, but it's not: specifically, Extension:EasyTimeline, which is installed on wikimedia wikis, treat all strings as if they were written from left to right. this means that for RTL strings, we need to reverse them manually, which was a major point of frustration for Timeline users on RTL wikis. i can't think of a good reason why mw.ustring should omit to provide the standard string function. peace - קיפודנחש (talk) 13:57, 15 June 2013 (UTC)
 * Because correctly reversing a Unicode string is non-trivial. You can't just reverse the codepoints, you have to divide the string into "abstract characters" (base characters plus any combining characters) or "grapheme clusters" and reverse those. And then you probably have to handle ties, bidi characters, and other such specially. Rather than trying to hack around it with Lua, it would probably be better to fix RTL support in Extension:EasyTimeline. Anomie (talk) 13:13, 17 June 2013 (UTC)
 * in principle i think you are correct, but in reality, it would be useful to have a reverse function with a footnote, explaining that this function actually reverses codepoints and not "abstract characters". true, there would be cases where this limitation would make reverse useless, or at least "less useful", but i can't see how the current state of affairs, with no "reverse" at all, is any better. for hebrew, at least (and i believe the situation is very similar for arabic), these "abstract characters" appear when the string uses something callsed Niqqud. this is optional, and telling the users "do not use niqqud in such and such situation" is far superior to telling them "if you want to use timeline, you have to supply the strings backwards", which is what happens now (and, btw, i do not think niqqud works with timeline anyway).
 * as to the "Rather than trying to hack around it with Lua, it would probably be better to fix RTL support in Extension:EasyTimeline": this problem plagued the use of "timeline" in RTL wikis for years and years (ever since timeline was introduced - i think around 2005 or maybe even earlier). it was not fixed in the years since then, and is not likely to be fixed ever.
 * Lua gave us a nice opportunity to work around the issue (i actually already implemented string reversing on hewiki, by utilizing mw.text.split, manually reversing the table, and then use table.concat. i just thought that since lua supports string.reverse, we should also have mw.ustring.reverse ).
 * peace - קיפודנחש (talk) 16:00, 17 June 2013 (UTC)

Example for string.format?
I read the description for string.format about 10 times, but I still don't really understand what it does. Would some kind person be willing to point me to an example or two? I have a feeling that it would be very useful in my coding, but I can't really grasp what it's used for at the moment. — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 12:05, 20 June 2013 (UTC)


 * Here is an extract of use the format function in my module to display coordinates and convert the angle value to text representation with specific accuracy, where
 * The roots of that interface come from the old printf from C language. In the example i.e. "%04.1f" prints float value passed with one digit after decimal point using 4 characters and padding with leading 0 if necessary. Paweł Ziemian (talk) 13:41, 20 June 2013 (UTC)


 * All this is heavily based on the C function printf. It's basically a way to concatenate strings and variables, applying formatting to the variables' values, in a way that can be more convenient than using the concatenation operator and individual functions to do the formatting operations.
 * The basic idea is that in a call like, the "%s" will be replaced by the value of the string variable 'var'. "%d" (or "%i") works the same for integers. "%o" will format an integer in octal and "%x" in hexadecimal, e.g.   results in "52 2a". "%e" will output a number in E notation, "%f" will format a number as a decimal with a fixed number of decimal places, and "%g" tries to be smart about choosing E notation versus decimal notation and trims trailing zeros in the decimal representation. For example,   results in "4.250000e+01 42.500000 42.5". "%c" takes an integer and outputs the corresponding character (as with  ). And "%%" is the escape in case you need a literal "%" character in your output.
 * Then there are the flags, width, and precision specifiers, which go between the "%" and the conversion specifier character. For example, using the width specifier as in "%10s" is like "%s", but it will pad with spaces on the left if the string is less than 10 bytes. If you add the '-' flag, as in "%-10s", it will pad on the right instead. "%10d" and "%-10d" work similarly; for the numeric conversions, you can also use the 0 flag (e.g. "%010d") to pad with zeros on the left instead of spaces. Precision truncates strings and specifies the number of digits after the decimal for "%f" and the like: "%.10s" will cut off the input string at 10 bytes, and "%.3f" will round to thousandths.
 * Lua leaves out a lot of the more complicated features in C's printf, though; the statements in the Scribunto Reference manual about things unsupported are for the benefit of people familiar with that so they can know what isn't available. And yes, someday I should probably make mw.ustring.format handle %s and %c using Unicode characters rather than bytes. Hope this helps. Anomie (talk) 13:59, 20 June 2013 (UTC)
 * Thank you Anomie and Paweł! Those explanations are both really helpful. As I suspected, this function looks really useful, and I will try it out right now. :) — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 01:44, 22 June 2013 (UTC)

Getting an Error with Italics
I am running a freebsd box and installed the latest lua port. I have been trying to get some of the wiki templates to work (specifically the SCOTUS) I keep getting "Script Error" all over the page. when I click on the link I get the following:

Lua error in Module:Citation/CS1 at line 186: attempt to index field 'text' (a nil value).

Backtrace:

(tail call): ? Module:Citation/CS1:186: in function "internallinkid" Module:Citation/CS1:591: in function "buildidlist" Module:Citation/CS1:1318: in function "buildidlist" (tail call): ? mw.lua:463: ? (tail call): ? [C]: in function "xpcall" MWServer.lua:73: in function "handleCall" MWServer.lua:266: in function "dispatch" MWServer.lua:33: in function "execute" mw_main.lua:7: in main chunk [C]: ?

If anyone can give me a clue as to what the problem might be. I tried removing and intalling the latest Parser and that didn't work either. It seems like it keeps throwing NIL or null values and I'm not sure why? Help!!!!


 * Hi there. It sounds like your version of Scribunto doesn't have the  library enabled. Try downloading the latest development version rather than the latest stable version, and see if that fixes your problem. Best — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 21:51, 2 July 2013 (UTC)


 * Thanks, I'll do that this afternoon when I get a chance. I'm currently running version 1.21 but I noticed that when I was looking at the snapshots there is a master development version as well....I'll use that one and see what happens.
 * Ok that seems to have solved the script error issue, but now the formatting is all messed up, do I need to download a new css file for this? [UPDATE] I deleted the CSS file and reloaded the copy from mediawiki and that made no difference. The formatting is all messed up now.
 * When you say that the formatting is all messed up, what do you mean? You'll need to give a bit more detailed description than that. Do you have an error message or a screenshot that you can give us? — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 09:04, 4 July 2013 (UTC)
 * I'm having a problem pasting a screen shot, here is a link to the page:

http://w[removeME]ww.i[RemoveMe]cce-t.n[RemoveMe]et/index.php/Roe_v._Wade I tried reloading the CSS file and that didn't make any difference, I'm just not sure what is screwed up now.
 * I guess nobody knows...
 * Still looking for some help with this one.
 * This doesn't look like a Scribunto problem. Instead, it is most likely that you are missing some necessary templates and/or modules. I think I managed to track the problem down to your wiki not having Template:Color - try uploading it and see if that makes things better. At any rate, things look much saner if you remove the "SCOTUS" parameter from the infobox in the page you linked. These kinds of problems are bound to crop up if you are relying on Wikipedia's templates, as they have been developed incrementally over 12 years and are, frankly, a big ol' mess. It's very easy to mess up a page because of missing dependencies, but then if you try and use all of Wikipedia's templates then things might start getting pretty slow. You'll have to experiment to find the best balance for you. — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 06:51, 15 July 2013 (UTC)

mw.title.compare
I have a quick question about  - what does it mean for a title to be less than, equal to, or greater than another title? Is it purely to do with the title length, or does it query the title text in some way? — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 09:07, 4 July 2013 (UTC)
 * When I invoke the lua code, it returns 0. It also returns 0 when I invoke  , so I don't understand me either. Automatik (talk) 10:39, 4 July 2013 (UTC)
 * compares two title objects, passing strings isn't going to work. It just compares the titles by,  , and  . You can see the Lua code behind it at . Anomie (talk) 13:00, 5 July 2013 (UTC)
 * Thanks you so much, I understand now. Automatik (talk) 01:19, 8 July 2013 (UTC)

Text library
mw.text library is unicode safe ? it say that add functions missing from mw.string that it's not unicode safe.--Moroboshi (talk) 09:10, 6 July 2013 (UTC)
 * Fixed. Anomie (talk) 13:45, 8 July 2013 (UTC)
 * Thanks! --Moroboshi (talk) 06:00, 9 July 2013 (UTC)

mw.site.namespaces
Hi,

Does anyone know what's the defaultContentModel which is in the mw.site.namespaces table? Thanks by advance, Automatik (talk) 01:36, 8 July 2013 (UTC)
 * With ContentHandler, each namespace has a default content model; often this is "wikitext", but this can be changed. For example, on wikidata.org the default content model for the main namespace is "wikibase-item". Anomie (talk) 13:47, 8 July 2013 (UTC)
 * Thank you. Automatik (talk) 18:13, 8 July 2013 (UTC)

check if a page exist on another project
I'm trying to use  to check if a page on project different from the project where i run the lua code exist. But i get a  on every page I try even if the page exist. Is possible to check the existence of a page from a project to another ?--Moroboshi (talk) 21:13, 18 July 2013 (UTC)
 * No, this is not possible. Anomie (talk) 13:23, 19 July 2013 (UTC)

Format text/plain is not supported
Hi,

I've try to import a XML file from wikipedia.org. At the end of the import, I obtain this error relevant to Scribunto :
 * Échec de l'importation : Format text/plain is not supported for content model Scribunto

Do you have any idea of its origin ? --Fractaliste (talk) 13:21, 23 August 2013 (UTC)
 * Chances are you are using an old version of Scribunto on your local wiki, see bug 51504 for discussion of a similar issue, and bug 45750 for the more general issue. Anomie (talk) 13:16, 26 August 2013 (UTC)


 * I use the last version of Scribunto. But I make it work with manualy changing text/plain with "CONTENT_FORMAT_TEXT"

--Fractaliste (talk) 12:24, 2 September 2013 (UTC)

Could you explain to me how you manually edited text/plain?

--Jurugo (talk) 14:30, 28 October 2013 (UTC)

frame:expandTemplate
seems not to work properly. While  works as expected,   doesn't, calling someTemplate without passing it any parametres. —The preceding unsigned comment was added by 178.72.109.160 (talk • contribs) 00:50, 22 September 2013 (UTC)
 * I just tried it at the English Wikipedia and it worked fine for me. Can you give us any details about your specific situation? — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 11:05, 23 September 2013 (UTC)
 * Note that if  was loaded by , this will be fixed by 84985. Anomie (talk) 13:31, 23 September 2013 (UTC)

Title object question
If we get a title object using, and then get the talk page title object using  , is the expensive function count incremented? It seems like it would be, but this is not obvious from the manual. And is this also true for basePageTitle, rootPageTitle, etc.? It would be good to know this to know which methods I should be calling with pcall. Thanks. :) — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 10:59, 23 September 2013 (UTC)
 * All of these create a new mw.title object, so yes. As noted in the manual, these are equivalent to calling  with the appropriate parameters, and makeTitle increments the expensive function count. Anomie (talk) 13:34, 23 September 2013 (UTC)
 * It's a bit late, but I've added "this is expensive" to the relevant title methods and properties. I know this is redundant to the notice in the makeTitle documentation, but I thought that it was probably better to be clear than to avoid redundancy. — <span style="color: #194D00; font-family: Palatino, Times, serif">Mr. Stradivarius  ♪ talk ♪ 04:31, 22 October 2013 (UTC)

mw.text.trim error
Hello. I'm trying to install some modules from WP on my personal wiki using scribunto extension. Most of them fail mainly because mw.text.trim returns an error "attempt to index field 'text' (a nil value).". I get this for example in the debug console if I type =mw.text.trim(' some string ') Is her any explanation why it fails ? Phcalle (talk) 12:15, 27 September 2013 (UTC)
 * You are using too old of a version of the Scribunto extension. In particular, the version marked as being for MediaWiki 1.21 is too old. See Extension talk:Scribunto for a history of other people discussing this same question. Anomie (talk) 13:56, 27 September 2013 (UTC)

Control structures "for"
have a default value then the line

probably should become:

Rical (talk) 15:40, 16 October 2013 (UTC)
 * The problem is that  and   both raise an error. The step value must be omitted entirely or given a numeric value, so it's not a real "default" value. Anomie (talk) 13:14, 17 October 2013 (UTC)
 * Enforce the value 1 in these cases could be misunderstood and disturbing for users. Keep the errors seems a good way to help the user to write a better code. Then we could write "A step value false or nil raise an error, else the default value is 1.". --Rical (talk) 18:05, 17 October 2013 (UTC)

«But if exp3 is nil, the for doesn't work.» : In this case, can we "break" the for and continue after end to solve this strange case without error ? "A nil value do nothing" seems normal. --Rical (talk) 02:05, 26 January 2014 (UTC)
 * We are not going to rewrite Lua's handling of for loops, if that's what you're asking. Anomie (talk) 15:36, 27 January 2014 (UTC)

Scope of variable example
The code example for "Function declarations" is not clear. Somehow it leaves out simple function naming, and introduces mw.log out of the blue. If it wants to illustrate a scope, there only should be some nesting right? I know about scope, but this example does not explain to me what it is in Lua. -DePiep (talk) 10:23, 18 November 2013 (UTC)
 * Do you have a suggestion on what to replace it with? Anomie (talk) 14:18, 18 November 2013 (UTC)

Insertion of excessive detail in Language module documentation
@‎Verdy p: Seriously, I doubt most Scribunto users care at all about the minutia of IETF language tags, BCP47, and how MediaWiki's language codes aren't exactly the same thing. And we certainly don't need big warnings all over the place to "warn" people that they aren't the same thing. Please don't revert again. If you have suggestions for actual improvement to the existing documentation beyond what I already incorporated from your original edit, please propose them here so we can discuss it. Thanks. Anomie (talk) 14:14, 18 November 2013 (UTC)


 * This is a reference. One would assume that it contains information that all users care about.
 * It certainly should be mentioned that “language code” here is not what one would assume. A standard language code is usable in HTML  attributes, while the non-standard strings returned by the Language Library can invalidate HTML.
 * A reasonable user who knows what “language code” means in the rest of the world would not bother following a link to “Language codes are described at Language code.” There should definitely be a warning evident in this reference that reasonable assumptions are incorrect. —Michael Z. 2013-11-18 16:35 z 


 * I don't understand the revert (my edits add been accepted previously by others than you, Anomie), these were absolutely not complains or excessive details of what these functions do or why these codes are not valid BCP47 codes which are required by the HTML standard. We still need a way to provide correct BCP47 codes even if Mediawiki (in fact Wikimedia sites) uses specific codes (in fact they are subdomain names for projects, not really language codes, but these codes have slipped into ther projects that use them now incorrectly; for example you can see "simple" being used in OpenStreetmap tags such as "name:simple=*" only because they have been borrowed from Wikipedia or now Wikidata using these bogous codes which are strictly internal to Wikimedia projects).
 * These codes should have never been in MediaWiki itself, and all should be done to deprecate them fast (this should also concern the translations of Mediawiki on translate.net). This legacy inheritence from Wikimedia projects includes also correctly explaining why the Language library does not validate these codes and why there are 4 functions but still none of them are able to support standard language codes; these functions also have differences that are NOT explained in the doc: my addition added these for reference. We still have a missing function for validating BCP47 codes (but only in PHP, not in the Scribunto Lua module).
 * These are not details. Conformance to standards is a legitimate goal that users assume, even in Wikimedia sites, but more importantly when other sites will use MediaWiki.
 * May be you don't care about this, Anomie, but many users, even the beginners, need to understand what these functions do, and also more importantly what they don't and what are their differences.
 * Verdy p (talk) 23:30, 18 November 2013 (UTC)
 * You appear to still be under the misapprehension that these functions are supposed to be dealing with IETF language codes. They're not. This is made clear in the documentation. There is no need to further belabor the point, just like we don't need big warnings on every screwdriver to say "This is not a hammer!". Anomie (talk) 14:07, 19 November 2013 (UTC)

frame.args
How can I check if frame.args is empty, since next (frame.args) is always nil? —The preceding unsigned comment was added by Alex Mashin (talk • contribs) 15:59, 2 January 2014 (UTC)
 * Chances are you don't actually need to do this, just check for the args you care about. But if you really do need it, try something like this:

Thank you, your code worked. Alex Mashin (talk) 14:48, 2 February 2014 (UTC)
 * Doing this will cause all the args (if any were passed) to be parsed, even if you're not going to use them otherwise. Anomie (talk) 14:37, 3 January 2014 (UTC)
 * Yes, I need to do this: I create Lua functions with dynamic (i.e. unpredictable) parametres often; and in this particular case, I wanted my Lua function to take all parametres from encapsulating template call when the function is invoked without arguments.

getContent returns the unparsed content, but how to return the interpreted one?
I've just wrote b:fr:Module:Version imprimable to create the printable versions of all Wikibooks by a single line. However the books pages are full of templates and they aren't displayed, eg: Programmation_XML/Version_imprimable.

b:pt:Módulo:Book seems to do it but I don't understand the trick for that please? JackPotte (talk) 12:19, 3 February 2014 (UTC)
 * Hi ! On b:pt:Módulo:Book the trick is in the line . I'm treating the page as if it was a template, and "transcluding" it in the printable version. Helder 12:31, 3 February 2014 (UTC)
 * Thank you, I'm going to try to call the pages as templates (even if they aren't in their namespace). JackPotte (talk) 12:37, 3 February 2014 (UTC)

frame:preprocess
On it.wiki there is a lua function that used mw.message:text method, now I switched to use frame:preprocess. I would like to known frame:preprocess has the same potential problem of mw.message:text and could be removed in the future.--Moroboshi (talk) 11:39, 19 February 2014 (UTC)
 * frame:preprocess is good. The problem with the mw.message methods was that MediaWiki's MessageCache class makes it's own instance of the parser and processes 'text', 'parse', and so on using that separate instance. So any categories, links, and such coming from the message were recorded on that separate parser instance and not on the parser instance that is being used to parse the actual page. frame:preprocess, on the other hand, uses the same parser instance that is being used to parse the page and therefore all the categories, links, and so on get recorded in the right place. Anomie (talk) 13:55, 19 February 2014 (UTC)
 * thanks for the explanation.--Moroboshi (talk) 12:34, 20 February 2014 (UTC)

getContentLanguage
On Wikimedia Commons the whole interface translates, if the user sets a language code in his/her preferences. However wgPageContentLanguage will always be 'en', so within the scope of commons it would be very useful to determine the language a user has set in prefs, to translate lua module output accordingly. getContentLanguage does not seem useful to do this as it just returns the default content language of the wiki, not the users. How do we read the language actually used by the user? This would be the one to care about if a Module should translate its messages, or am I mistaken something fundamentally here? mw.message seems to only fit system messages and cannot advance to include module owned translation tables as I get it. Thanks for comments, recommendations. --Cmuelle8 (talk) 03:47, 10 March 2014 (UTC)
 * I've found some code in Module:Languages on commons, but I doubt this should do in the long run, should it? I have not tried it, but it looks ugly, since a normal template is preprocessed - just to get the users language..


 * The problem here is that Lua == content language, because it is server side and generates content. The trick above also really shouldn't be used. Content gets cached, and the above trick would mean a german user could get chinese content. For now, commons will have to remain using Javascript. TheDJ (talk) 11:37, 10 March 2014 (UTC)
 * Yes, the "int:lang" thing Commons uses all over the place is a bit of a hack, and it's not going to be supported in Scribunto other than by using the hack as above. I haven't actually tested it, but using int: via frame:preprocess shouldn't be any worse than using it in wikitext (i.e. it should fragment the cache based on user language, but shouldn't cause issues like bug 14404). Anomie (talk) 14:31, 10 March 2014 (UTC)

Tabel description
About the table definition (mw:Extension:Scribunto/Lua_reference_manual). The example code now has

I understand that it is not essential that the key and value are alike. Also accepted are: This is to improve (my understanding of) the documentation. -DePiep (talk) 18:54, 6 April 2014 (UTC)
 * Just now I had to try 2n tests to relearn how numbers can and cannot be defined in a table. Great. -DePiep (talk) 20:26, 12 June 2014 (UTC)

Examples
Sigh. I count 239 functions and not a single example. What am I supposed to know beforehand? Is there a secret class to follow? -DePiep (talk) 10:01, 7 April 2014 (UTC)
 * This is a reference manual, not a textbook. While a textbook would be an excellent idea, this shouldn't be it. Anomie (talk) 13:26, 7 April 2014 (UTC)
 * Use links. New to internet? (Or conversely you should remove the unwanted example here)
 * At least, I expected helpful links. -DePiep (talk) 05:49, 8 April 2014 (UTC) anger management & direction -DePiep (talk) 10:06, 8 April 2014 (UTC)

How to use "next" ?
It is not so easy to understand how to use. I used it in a local table with keys [1] and ["1"]. Could you add the right use : "for k, v in next, table" ? --Rical (talk) 09:10, 14 April 2014 (UTC)
 * In a for loop, you'd probably want to use "for k, v in pairs( table )" instead of trying to use 'next' directly.
 * To use next, you call it the first time as "k = next( table, nil )" (or just "k = next( table )") and then subsequent times as "k = next( table, k )". When the returned key is nil, you've reached the end of the table. Anomie (talk) 13:26, 14 April 2014 (UTC)
 * If we use an  loop, then a   loop, we must duplicate all the process inside with only a very small difference difficult to locate and to maintain. If we use   we write only once the process and the small difference become explicit and easy to maintain.
 * The fonction  exists and is usefull in some cases, anywhere, not necessary for read arguments. Like all others, it deserves a full description. --Rical (talk) 00:13, 15 April 2014 (UTC)
 * Functionality-wise and absent a __pairs metamethod, there is no difference between  and  . So I'm not following what you're trying to get at here. Anomie (talk) 13:22, 15 April 2014 (UTC)

Using a pattern capture
See Extension:Scribunto/Lua_reference_manual. Captures does not describe how to reuse a numbered capture (try  or  ?). -DePiep (talk) 17:01, 13 April 2014 (UTC)
 * What, like ? This is described slightly earlier in the document under "Pattern items": ", for n between 1 and 9; such item matches a substring equal to the n-th captured string (see below)". Anomie (talk) 13:23, 14 April 2014 (UTC)
 * So my statement is confirmed, thank you. Now how can we improve the documentation? -DePiep (talk) 19:15, 17 April 2014 (UTC)
 * Great. So you say: to understand the documentation, read its talkpage. That is where the links are! -DePiep (talk) 20:35, 12 June 2014 (UTC)

Lua error: too many language codes requested.
According to the documentation Lua calls are preferable to callParserFunction calls. So I was trying to replace with Both work just fine for individual examples, but I run into "Lua error: too many language codes requested." on my c:Module talk:Date/sandbox/testcases test page. Any way to avoid that error, other than not using formatDate? --Jarekt (talk) 15:53, 16 June 2014 (UTC)
 * Split the page up so it doesn't try to use more than 20 language codes per page. Anomie (talk) 13:04, 17 June 2014 (UTC)

work with media files
I am wondering if it is possible to work with media files using Lua.

My situation: I have the URL to a video, that I can get to look nice using wikitext via Lua:

But I do not want to have an embedded player, I want to show the respective thumbnail and define my own link target. Unfortunately I am not aware of how I can access this thumbnail.

For a quick-n-dirty solution I tried to use  in order to extract the image path with string magic, but preprocess does not process such a file expression.

How can I get the path of the thumbail of a video? Is there a Lua library I am not aware of that handles media files? Any other ideas how to do that?

Greetings --Sebschlicht (talk) 16:53, 16 July 2014 (UTC)
 * It's currently not possible to do that. Jackmcbarn (talk) 03:22, 17 July 2014 (UTC)