Fix for l/rpad with > 1 length padding string

Also, tests for JuliaLang#11885.

Author: Pontus Stenetorp

base/string.jl

@@ -1252,7 +1252,8 @@ function lpad(s::AbstractString, n::Integer, p::AbstractString=" ")
     end
     q = div(m,l)
     r = m - q*l
-    bytestring(p^q*p[1:chr2ind(p,r)]*s)
+    i = r != 0 ? chr2ind(p, r) : -1
+    bytestring(p^q*p[1:i]*s)
 end
 
 function rpad(s::AbstractString, n::Integer, p::AbstractString=" ")
@@ -1264,7 +1265,8 @@ function rpad(s::AbstractString, n::Integer, p::AbstractString=" ")
     end
     q = div(m,l)
     r = m - q*l
-    bytestring(s*p^q*p[1:chr2ind(p,r)])
+    i = r != 0 ? chr2ind(p, r) : -1
+    bytestring(s*p^q*p[1:i])
 end
 
 lpad(s, n::Integer, p=" ") = lpad(string(s),n,string(p))

test/strings.jl

@@ -253,6 +253,15 @@ for T in (UInt8,UInt16,UInt32,UInt64)
     @test_throws OverflowError parse(T,string(big(typemax(T))+1))
 end
 
+@test lpad("foo", 3) == "foo"
+@test rpad("foo", 3) == "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   "
+
 # string manipulation
 @test strip("\t  hi   \n") == "hi"