lpad, rpad: use character cound instead of textwidth [fix #25016] (#25069)

The general principle here is that we should avoid having behavior in Base that depends on which version of Unicode you're using. It's fine for an external package to provide versions of lpad and rpad which use textwidth and thereby depend on Unicode details, but the functions in Base should not depend on these.

Author: StefanKarpinski

base/deprecated.jl

@@ -3033,6 +3033,10 @@ end
 # Associative -> AbstractDict (#25012)
 @deprecate_binding Associative AbstractDict
 
+# issue #25016
+@deprecate lpad(s, n::Integer, p) lpad(string(s), n, string(p))
+@deprecate rpad(s, n::Integer, p) rpad(string(s), n, string(p))
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/strings/util.jl

@@ -204,49 +204,59 @@ strip(s::AbstractString, chars::Chars) = lstrip(rstrip(s, chars), chars)
 
 ## string padding functions ##
 
-function lpad(s::AbstractString, n::Integer, p::AbstractString=" ")
-    m = n - Unicode.textwidth(s)
-    m ≤ 0 && return s
-    l = Unicode.textwidth(p)
-    q, r = divrem(m, l)
-    string(p^q, first(p, r), s)
-end
-
-function rpad(s::AbstractString, n::Integer, p::AbstractString=" ")
-    m = n - Unicode.textwidth(s)
-    m ≤ 0 && return s
-    l = Unicode.textwidth(p)
-    q, r = divrem(m, l)
-    string(s, p^q, first(p, r))
-end
-
 """
-    lpad(s, n::Integer, p::AbstractString=" ")
+    lpad(s, n::Integer, p::Union{Char,AbstractString}=' ') -> String
 
-Make a string at least `n` columns wide when printed by padding `s` on the left
-with copies of `p`.
+Stringify `s` and pad the resulting string on the left with `p` to make it `n`
+characters (code points) long. If `s` is already `n` characters long, an equal
+string is returned. Pad with spaces by default.
 
 # Examples
 ```jldoctest
-julia> lpad("March",10)
+julia> lpad("March", 10)
 "     March"
 ```
 """
-lpad(s, n::Integer, p=" ") = lpad(string(s),n,string(p))
+lpad(s, n::Integer, p::Union{Char,AbstractString}=' ') = lpad(string(s), n, string(p))
+
+function lpad(
+    s::Union{Char,AbstractString},
+    n::Integer,
+    p::Union{Char,AbstractString}=' ',
+) :: String
+    m = n - length(s)
+    m ≤ 0 && return string(s)
+    l = length(p)
+    q, r = divrem(m, l)
+    r == 0 ? string(p^q, s) : string(p^q, first(p, r), s)
+end
 
 """
-    rpad(s, n::Integer, p::AbstractString=" ")
+    rpad(s, n::Integer, p::Union{Char,AbstractString}=' ') -> String
 
-Make a string at least `n` columns wide when printed by padding `s` on the right
-with copies of `p`.
+Stringify `s` and pad the resulting string on the right with `p` to make it `n`
+characters (code points) long. If `s` is already `n` characters long, an equal
+string is returned. Pad with spaces by default.
 
 # Examples
 ```jldoctest
-julia> rpad("March",20)
+julia> rpad("March", 20)
 "March               "
 ```
 """
-rpad(s, n::Integer, p=" ") = rpad(string(s),n,string(p))
+rpad(s, n::Integer, p::Union{Char,AbstractString}=' ') = rpad(string(s), n, string(p))
+
+function rpad(
+    s::Union{Char,AbstractString},
+    n::Integer,
+    p::Union{Char,AbstractString}=' ',
+) :: String
+    m = n - length(s)
+    m ≤ 0 && return string(s)
+    l = length(p)
+    q, r = divrem(m, l)
+    r == 0 ? string(s, p^q) : string(s, p^q, first(p, r))
+end
 
 # splitter can be a Char, Vector{Char}, AbstractString, Regex, ...
 # any splitter that provides search(s::AbstractString, splitter)

test/strings/util.jl

@@ -1,14 +1,46 @@
 # This file is a part of Julia. License is MIT: https://julialang.org/license
 
 @testset "padding (lpad and rpad)" begin
+    @test lpad("foo", 2) == "foo"
+    @test rpad("foo", 2) == "foo"
     @test lpad("foo", 3) == "foo"
     @test rpad("foo", 3) == "foo"
+    @test lpad("foo", 4) == " foo"
+    @test rpad("foo", 4) == "foo "
     @test lpad("foo", 5) == "  foo"
     @test rpad("foo", 5) == "foo  "
-    @test lpad("foo", 5, "  ") == "  foo"
-    @test rpad("foo", 5, "  ") == "foo  "
-    @test lpad("foo", 6, "  ") == "   foo"
-    @test rpad("foo", 6, "  ") == "foo   "
+    @test lpad("foo", 2, "123") == "foo"
+    @test rpad("foo", 2, "123") == "foo"
+    @test lpad("foo", 3, "123") == "foo"
+    @test rpad("foo", 3, "123") == "foo"
+    @test lpad("foo", 4, "123") == "1foo"
+    @test rpad("foo", 4, "123") == "foo1"
+    @test lpad("foo", 5, "123") == "12foo"
+    @test rpad("foo", 5, "123") == "foo12"
+    @test lpad("foo", 6, "123") == "123foo"
+    @test rpad("foo", 6, "123") == "foo123"
+    @test lpad("foo", 7, "123") == "1231foo"
+    @test rpad("foo", 7, "123") == "foo1231"
+    @test lpad("foo", 8, "123") == "12312foo"
+    @test rpad("foo", 8, "123") == "foo12312"
+    @test lpad("foo", 9, "123") == "123123foo"
+    @test rpad("foo", 9, "123") == "foo123123"
+    @test lpad("αβ", 2, "¹₂³") == "αβ"
+    @test rpad("αβ", 2, "¹₂³") == "αβ"
+    @test lpad("αβ", 3, "¹₂³") == "¹αβ"
+    @test rpad("αβ", 3, "¹₂³") == "αβ¹"
+    @test lpad("αβ", 4, "¹₂³") == "¹₂αβ"
+    @test rpad("αβ", 4, "¹₂³") == "αβ¹₂"
+    @test lpad("αβ", 5, "¹₂³") == "¹₂³αβ"
+    @test rpad("αβ", 5, "¹₂³") == "αβ¹₂³"
+    @test lpad("αβ", 6, "¹₂³") == "¹₂³¹αβ"
+    @test rpad("αβ", 6, "¹₂³") == "αβ¹₂³¹"
+    @test lpad("αβ", 7, "¹₂³") == "¹₂³¹₂αβ"
+    @test rpad("αβ", 7, "¹₂³") == "αβ¹₂³¹₂"
+    @test lpad("αβ", 8, "¹₂³") == "¹₂³¹₂³αβ"
+    @test rpad("αβ", 8, "¹₂³") == "αβ¹₂³¹₂³"
+    @test lpad("αβ", 9, "¹₂³") == "¹₂³¹₂³¹αβ"
+    @test rpad("αβ", 9, "¹₂³") == "αβ¹₂³¹₂³¹"
 end
 
 # string manipulation