On Wed, Jun 5, 2013 at 8:22 PM, MZMcBride &lt;z(a)mzmcbride.com&gt; wrote: The debug console seems finicky. Its line numbers never seem to make The console isn't designed to handle blocks of code. You should compose blocks of code into the module itself and use the debug console for simple poking and prodding. You don't have to save the page: unsaved modifications to the page are reflected to the console. For example, go edit a module page, and paste this snippet into the code editor: -- local p = {} function p.greet(name) return "Hello, " .. name end return p -- Then in the debug console, type: =p.greet("Lua") Hello, Lua Lua error in console input at line 6: attempt to index local 'frame' (a That's because you wrote a function that accesses a "frame" parameter, but you don't provide a value for it. You'll get a similar error if you omit the name from the invocation of the 'greet' function we wrote earlier: =p.greet() Lua error at line 4: attempt to concatenate local 'name' (a nil value). Note that the error cites the correct line number: it's indeed the 'return' statement in p.greet that is causing the error. In some programming languages, like Python, arguments without defaults are required, and it is an error to omit them from the invocation. In Lua and some other languages the value of any parameter that is absent from the invocation is set to nil, so p.greet() is equivalent to p.greet(nil). I have no idea what line 6 refers to. Earlier when I was testing it was I think your confusion resulted from trying to work with blocks of code in the debug console. "frame" can be a bit tricky to grasp and trickier still to work with, but once you get it, it's not so bad. The way Scribunto handles {{#invoke}} is this: first, it makes a table. This is the 'frame' table. Then it makes an 'args' table inside that table. Then it puts the arguments into the 'args' table. Then it calls your function, passing the frame table as the sole parameter. When the parser invokes a Lua function from an {{#invoke}}, it *always* passes exactly one parameter: frame. It doesn't matter what arguments (if any) were present in {{#invoke}} or what your function thought it was getting. It's getting a frame and it's going to like it. As an example, here's Lua code that is (very roughly) equivalent to how Scribunto would handle {{#invoke:Sort|asc|3|1|2}} -- frame = {} frame.args = { 3, 1, 2 } sort = require('Module:Sort') sort.asc(frame) -- This is a bit annoying, because at first glance "invoke" looks like it's just an alternate syntax for a Lua function invocation, so you expect {{#invoke:Sort|asc|3|1|2}} to be equivalent to sort.asc(3, 1, 2), but that's not the case. So, how do we work with this? I can recommend two approaches. For the purpose of demonstrating them, let's imagine we want to write a Scribunto math module that has a function, 'sum', that takes two numbers and adds them. One approach is work with a frame parameter from the get-go. -- local p = {} function p.sum(frame) return frame.args[1] + frame.args[2] end return p -- This works if we save it and then try to invoke it from somewhere: {{#invoke:Math|sum|4|5}} should evaluate to 9. But how do we test it in the debug console? We'll pretend we're the parser and make our own frame table. Paste the code block above into a module, and type this into the debug console, hitting <return> after each line: frame = {} frame.args = { 4, 5 } =p.sum(frame) With any luck, you'll get '9'. You can make this shorter by creating both tables at once: frame = { args = { 4, 5 } } =p.sum(frame) Or even: =p.sum({ args = {4, 5} }) Because calling a function with a table as the parameter is very common, Lua has a special syntax for it, which lets you omit the parentheses: =p.sum{ args = { 4, 5 } } All of the variants above are equivalent. The second approach is to not deal with frames until you have to. This workflow works especially well when you're developing on your own computer, using the standard Lua interpreter. Just write a normal Lua function and verify that it works. -- local p = {} function p.sum(a, b) return a + b end return p -- You can test that it works with =p.sum(4, 5). When you're ready to save your module, write a helper function that takes a frame table and uses it to call your actual function. -- local p = {} function p.sum_real(a, b) return a + b end function p.sum(frame) return p.sum_real(frame.args[1], frame.args[2]) end return p -- This lets you test your function easily from the console, using 'sum_real': =p.sum_real(4,5) 9 But 'sum' works from wikitext as expected: {{#invoke:Math|sum|4|5}} will evaluate to 9. There's a note on the edit screen about using mw.log(), but with various Works for me. Try this example: -- local p = {} function p.greet(name) mw.log("I got: " .. name) return "Hello!" end return p -- In the console: =p.greet("Lua") I got: Lua Hello! You're not missing anything, except maybe a plane ticket to Brazil so you can throw a glass of dirty water at the creators of Lua. There's no single, simple, straightforward way to print a table in Lua. You have to write it yourself or use a library. The mind reels. There's probably a helper in the mw library somewhere. Is there a better way to write/debug Lua modules? Any help writing these If you're writing something that doesn't need to talk with MediaWiki via the Scribunto API, it's sometimes easier to develop and test locally and then refactor it to use frame.args as a last step before saving it as a module. I also often use my tiny Scribunto REPL ( https://gist.github.com/atdt/5382043). Just save it as "scrib" somewhere in your $PATH. -- Ori Livneh

On Wed, Jun 5, 2013 at 11:22 PM, MZMcBride &lt;z(a)mzmcbride.com&gt; wrote: The debug console probably could use some work. The way it works now, it takes your past and current input, plugs all that into some boilerplate to make a function, and then executes that function. The line numbers reported for "Lua error in console input" therefore depend on this boilerplate and on the lines you've previously entered in the session. It's also possible to break that boilerplate function, as you've seen below. It's referring to which line in that boilerplate function the "return frame.args[1]" ended up at. Yes, that's not extremely helpful. [SNIP] This is an example of breaking the boilerplate function. In Lua, it's an error to have unreachable code after a return statement. When you put "return p" into the debug console like that, the boilerplate function winds up looking something like this: function ( p ) local print = mw.log -- Previous lines go here mw.clearLogBuffer() return p -- This is the line you entered return nil, mw.getLogBuffer() -- This is boilerplate end Again, the console should probably be made more robust at some point to avoid this sort of thing. That's because you're defining a function but not calling it (yet). Since 't' is a local variable inside the function, it's not defined outside of it. Not yet. -- Brad Jorsch Software Engineer Wikimedia Foundation

On Wed, Jun 5, 2013 at 8:22 PM, MZMcBride &lt;z(a)mzmcbride.com&gt; wrote: <snip> I edited your code to make the Sort Module do what I think you intended it to do. -Robert