Help:Lua debugging: Difference between revisions

Revision as of 10:49, 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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=== 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 ===

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[[Category:Wikipedia how-to]]

[[Category:Wikipedia text help]]

[[Category:WikipediaModule moduleshelp|Debugging]]