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LuaMultiReturn returns all values even when indexed with [0] #1411

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Cheatoid opened this issue Feb 26, 2023 · 0 comments · Fixed by #1428
Closed

LuaMultiReturn returns all values even when indexed with [0] #1411

Cheatoid opened this issue Feb 26, 2023 · 0 comments · Fixed by #1428
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bug scope: language extensions Related to language-extension types scope: transformation Transformation of TS to Lua

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@Cheatoid
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See Playground sample.

I expected that foo would have transpiled to (notice parentheses):

function foo(str)
    return (string.gsub(str, ".", "*"))
end

But, it clearly doesn't and therefore leads to multiple returns, because string.gsub also returns the amount of replacements as a secondary return value, which invalidates the specified return type : string of the foo... It works fine in case of bar and baz since they make use of a variable.
@Perryvw Perryvw added bug scope: transformation Transformation of TS to Lua scope: language extensions Related to language-extension types labels Feb 26, 2023
@Perryvw Perryvw changed the title A small bug related to LuaMultiReturn LuaMultiReturn returns all values even when indexed with [0] Feb 26, 2023
lolleko added a commit that referenced this issue Apr 10, 2023
@lolleko
Fixed multi returning all values
c643296 
We try to avoid using `select()` when we use `[0]` to access the first value of multiple returns (e.g. `multiCall()[0]`)
In that case, we used to simply omit the `select()`. Unfortunately, this only works if the value is assigned directly (`local x = multiCall()`). In cases where the value is not assigned, omitting the select and keeping the original expression (`multiCall()`) will lead to all return values being passed on.
(See #1411)

To fix this, we now wrap the multireturncall in parentheses. using a new Lua parentheses expression. Using parenthesis is the correct way to keep only the first value of multiple returns (see https://www.lua.org/manual/5.1/manual.html#2.5)

This fixes #1411
This was referenced Apr 10, 2023
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Perryvw pushed a commit that referenced this issue Apr 12, 2023
@lolleko
Fixed multi returning all values (#1428)
d13f800 
We try to avoid using `select()` when we use `[0]` to access the first value of multiple returns (e.g. `multiCall()[0]`)
In that case, we used to simply omit the `select()`. Unfortunately, this only works if the value is assigned directly (`local x = multiCall()`). In cases where the value is not assigned, omitting the select and keeping the original expression (`multiCall()`) will lead to all return values being passed on.
(See #1411)

To fix this, we now wrap the multireturncall in parentheses. using a new Lua parentheses expression. Using parenthesis is the correct way to keep only the first value of multiple returns (see https://www.lua.org/manual/5.1/manual.html#2.5)

This fixes #1411
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bug scope: language extensions Related to language-extension types scope: transformation Transformation of TS to Lua
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Fixed multi returning all values TypeScriptToLua/TypeScriptToLua
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@Perryvw @Cheatoid