Blockly: Lua generator's multiline_quote_ produces invalid code

[seldomU]

Even for single-line literals like foo, this is not valid Lua: [===foo===]. The form [===[foo]===] is valid , but has problems with multi-line inputs: the linebreak backslashes end up in the string.

[alschmiedt]

From what I can tell the appropriate fix here would be to simply return '[=[' + string + ']=]'; from the multiline_quote_ method and to remove the string.replace calls since "Escape sequences are not recognized when using double brackets" (found here).

However, this is my first time looking at lua. @seldomU is this along the lines of what you would expect?

[rachel-fenichel]

I'm also not a Lua user, but I see two possible solutions to this + #3978 for Lua.

I'll use this block stack for examples:

1) Use string concatenation: generate code that looks like this:

for count = 1, 10 do
  print('this is\n'..
  'a\n'..
  'multiline\n'..
  'string')
end

This is obviously slightly slower because of concatenation, but the case of many concatenations in a loop is not something we're going to optimize for.

2) Use the \z escape sequence, as described here.

for count = 1, 10 do
  print("this is \n\z
  a \n\z
  multiline \n\z
  string")
end

Option 2 is for Lua 5.3 and up. repl.it is stuck at 5.1, but 5.3 is from 2015 so it seems relatively safe to me.
Option 2 does have the problem that ignores all leading whitespace, which means you get the same output with this code:

for count = 1, 10 do
  print("this is \n\z
    a \n\z
   multiline \n\z
  string")
end

As a result, I prefer option 1.

@seldomU You're the current authority on Lua, so let us know what you think is best.

[seldomU]

My Lua skills consist mostly of taking Blockly generated code, feeding it into my game's interpreter and hoping for the best. So I feel well qualified for calling the shots.

I prefer Option 1 for its compatibility. I checked my interpreter (MoonSharp) as well as Roblox and both don't support Lua 5.3 yet. I'm not worried about concatenation being slightly slower.