[feature request] String interpolation for logging

[SkyyySi]

In Python, there's a useful little feature that allows writing something like the following:

foo = "bar"
print(f"{foo = }")

which prints:

foo = 'bar'

Notice how it preserved the spaces before and after the equals sign as written in the f-string.

I think this feature would be a very nice addition to Yuescript, although it may need some simplification. In Python, the code actually translates to printing the repr of foo, not the string conversion; an equivalent would be to write print("foo = " + repr(foo)). But of course that doesn't exist in Lua. My suggestion would be to either just print the value's tostring(), or maybe using a library function to pretty print it. While Yuescript seems to generally prefer inlining things to prevent being dependent on any libraries, I believe it would be fine here, because this is a pure development/debugging feature, so it's pretty safe to expect someone to have Yuescript installed if their code makes use of it.

[pigpigyyy]

I'm currently using a pretty print function taken from Moonscript's library. You can use it as:

import "yue" as :p
foo = "bar"
tb = {1, 2,3, abd: 123}
p foo
p tb

So you suggest that we can make some pretty print function code inlined, so that we can do it without importing extra libs?

[SkyyySi]

So you suggest that we can make some pretty print function code inlined, so that we can do it without importing extra libs?

No that's not what I meant. I talked about pretty printing a little too much at the end of my post so I probably should have made it more clear that that wasn't the focus. Instead, the important take away was actually the logging syntax for string interpolation. I didn't know that Yuescript already has a pretty printing function in its library, so I didn't mention it originally.

The thing I was talking about would be this:

foo = "bar"
print "#{foo = }"

which would compile to something like this:

_pretty_0 = require("yue").p
local foo = "bar"
print("foo = " .. _pretty_0(foo))

[SkyyySi]

@pigpigyyy Hey, I was just wondering, is this still something that's considered to be added? Even if it were to be the most basic form (like below), I would personally still find it immensely useful since I use print-debugging... way more than I probably should 😅

print "#{expression = }"

print("expression = " .. tostring(expression))

[pigpigyyy]

How about using a macro for better logging?

macro d = (...) ->
  import "yue" as options: :release
  unless release
    "print " .. table.concat ["\"#{v} = \" .. tostring(#{v})" for v in *{...}], ","
  else
    ""

tb =
  a: 123
  b: "abc"
val = 998
s = "xyz"

$d tb, val, s
nil

when builds with:

> yue test.yue

gets:

local tb = {
  a = 123,
  b = "abc"
}
local val = 998
local s = "xyz"
do
  print("tb = " .. tostring(tb), "val = " .. tostring(val), "s = " .. tostring(s))
end
return nil

builds with:

> yue --release test.yue

gets:

local tb = {
  a = 123,
  b = "abc"
}
local val = 998
local s = "xyz"
return nil