Help:Lua debugging: Difference between revisions

Revision as of 10:19, 27 November 2021

Latest revision as of 15:03, 16 June 2024

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{{WikiProject Lua header}}

This help-page, '''Help:Lua debugging''', explains issues of writing [[Lua (programming language)|Lua script]] and [[debugging]] the [[source code]], to remove errors or improve performance. Because Lua is a "semi-compiled" interpreted language, it does not prescreen for all common syntax errors, nor detect misspelled variables, which are only found at runtime when seeing the "{{Script error}}" message. Also, unlike [[wp:template]]s which can be run interactively by edit-preview, the Lua script must be tested by show-preview (or run preview) of another page which uses a template which <code>#invoke</code>'s the Lua module being edited. In general, make one small change at a time, do a run show-preview, and save after a few good changes to have a version to restore, in case terrible errors occur after numerous later changes. Note: the saving of a working copy can be done to an offline text file, rather than saving each version into the module revisions.

Other pre-compiled, or semi-compiled, languages can pinpoint the line number, or code phrase, where a syntax error, or undefined variable name, has been detected; however, that processing can require extra time to perform. Instead, it might be possible to use a [[lexical analysis]] tool, specifically for Lua script, to better detect and pinpoint misspelled variables or logic errors in Lua source code.

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! Request !! Returned value

|-

| {{colorcode|blue2=lua|mw.log(p.Hello)}}|| {{samp|"Hello"}}

|-

| {{colorcode|blue2=lua|mw.log(p.calc(10/2))}} || {{samp|5}}

|-

| {{colorcode|blue2=lua|mw.log(p.sum_mult(3))}} || {{samp|6&nbsp;&nbsp;&nbsp;9}}

|-

| {{colorcode|blue2=lua|mw.log(p.mtable(4))}} || {{samp|table}}

|-

| {{colorcode|blue2=lua|mw.logObject(p.mtable(4))}} || {{sxhl|2=lua|

table#1 {

:4,

:5,

}

}}

|-

| {{bluecode|2=lua|{{=}}p.sum_mult(10)}} || {{samp|20 100}}

|-

| {{bluecode|2=lua|{{=}}p.Hello .. ', World!'}} || {{samp|Hello, World!}}

|}

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=== Small caveat: The case of the wrong case ===

Wikipedia has a small perversion regarding page name casing: it will convert the first character of a page name to uppercase, regardless of the way it was entered. To compensate, it also converts the first letter of a template (when transcluded) and module (when invoked) to uppercase. however, this does not extend to the modules stored in User: namespace viewed through the special [[Template sandbox]], because in the sandbox "the first letter" is not the first letter any more. Here is an actual example: for real modules, let's say [[Module:String]], mediawiki software will allow you to use <nowiki>{{#invoke:mlx|String|replace|Hara I am|a|e}}</nowiki> to return "Here I em" (try it). It will also allow you to use <nowiki>{{#invoke:mlx|string|replace|Hara I am|a|e}}</nowiki> to get the same result:

{|class="wikitable"

|-

! wikitext !! result

|-

|<nowiki>{{#invoke:mlx|String | replace | Hara I am |a|e}}</nowiki>||{{#invoke:String | replace | Hara I am |a|e}}

|-

|<nowiki>{{#invoke:mlx|string | replace | Hara I am |a|e}}</nowiki>||{{#invoke:string | replace | Hara I am |a|e}}

|}

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The overall effort appears unstable, or unreliable, as if Lua suddenly "gets too tired" and starts complaining by storing "Script error" into the resultant page, where formatted text would have been expected instead. The timeout problem is somewhat rare, and when a formatted article contains "Script error" text inside the page, then perhaps edit the page slightly, to make a small change, to force the replacement of the page with a clean Lua run.

== Exasperating bugs ==

{{Main|Help:Lua for beginners#Exasperating bugs}}

== Off-wiki tools ==

=== IDE ===

Running your code through an IDE is helpful for its text highlighting features, which can help you quickly spot syntax errors. Any IDE with the ability to install a Lua text highlighting plugin should work. This could be as simple as [[Notepad++]] (with Lua selected from the language menu) or as full-featured as [[Visual Studio Code]].

=== Step debugger ===

Step debugging is a powerful tool that allows you to step through code one line at a time, and hover over variables to see their contents at the time of execution. IDEs that easily support Lua step debugging include [[ZeroBrane Studio]], and [[IntelliJ IDEA]] with itsvarious debugger plugins ([https://plugins.jetbrains.com/plugin/9768-emmylua Emmy Lua] pluginor [https://github.com/Benjamin-Dobell/IntelliJ-Luanalysis Lunalysis]).

=== RegEx ===

{{See also|mw:Extension:Scribunto/Lua reference manual#Patterns}}

Lua uses a unique flavor of [[Regular expression|regular expressions]] that is not supported by top RegEx tools. One tool that can be used for checking Lua RegEx includesis [https://gitspartv.github.io/lua-patterns/ GitSparTV's Lua patternsPatterns].

== Support ==

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== See also ==

* [[Wikipedia:Lua]]

* [[wp:Lua in Wikipedia]] - essay about using [[Lua script]] in Wikipedia

* [[Template:Wikipedia help pages]] - large navbox linking to other topics

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[[Category:Wikipedia how-to]]

[[Category:Wikipedia text help]]

[[Category:WikipediaModule moduleshelp|Debugging]]