The String Capitalize Function Doesn't Handle Apostrophes Correctly Resulting In Bad Output

[timkrief]

Tested versions

Tested in 3.5.2 and 4.2.stable

System information

Latest Ubuntu LTS

Issue description

In French, if I want to capitalize "le feu" it will output "Le Feu" correctly. But if the word starts with a vowel, the "le" is shortened as "l'", and in that case "l'eau" capitalized should output "L'Eau" but it outputs "L'eau".

Steps to reproduce

You can just run this line to see the issue:
print("L'eau ça mouille".capitalize())

Results in:
L'eau Ça Mouille

Minimal reproduction project (MRP)

extends Node

func _ready():
	print("L'eau ça mouille".capitalize())

[bruvzg]

String.capitalize only handle spaces and _.

capitalized should output "L'Eau" but it outputs "L'eau"

Every app I have tried do exactly the same thing.

For 4.x, it should be possible to expose a language specific variant for this function from ICU used in the TextServer, but in this case it's also doing exactly the same.

[ajreckof]

I wouldn't expect a word after an apostrophes to be capitalised and that independent of the language.
On the note of apostrophes and french would you also expect "aujourd'hui" to be capitalised as "Aujourd'Hui"?

[timkrief]

"Aujourd'hui" would be an exception, which makes me think that I think it's better to keep this function as is and create custom or langage specific capitalize functions.