Fixes constructor of SubString from SubString

NEWS.md

@@ -608,6 +608,9 @@ Breaking changes
 
 This section lists changes that do not have deprecation warnings.
 
+  * The constructor of `SubString` now checks if the requsted view range
+    is defined by valid indices in the parent `AbstractString` ([#22511]).
+
   * `readline`, `readlines` and `eachline` return lines without line endings by default.
     You *must* use `readline(s, chomp=false)`, etc. to get the old behavior where
     returned lines include trailing end-of-line character(s) ([#19944]).

base/regex.jl

@@ -178,9 +178,10 @@ function match(re::Regex, str::Union{SubString{String}, String}, idx::Integer, a
     end
     ovec = re.ovec
     n = div(length(ovec),2) - 1
-    mat = SubString(str, ovec[1]+1, ovec[2])
-    cap = Union{Void,SubString{String}}[
-            ovec[2i+1] == PCRE.UNSET ? nothing : SubString(str, ovec[2i+1]+1, ovec[2i+2]) for i=1:n ]
+    mat = SubString(str, ovec[1]+1, prevind(str, ovec[2]+1))
+    cap = Union{Void,SubString{String}}[ovec[2i+1] == PCRE.UNSET ? nothing :
+                                        SubString(str, ovec[2i+1]+1,
+                                                  prevind(str, ovec[2i+2]+1)) for i=1:n]
     off = Int[ ovec[2i+1]+1 for i=1:n ]
     RegexMatch(mat, cap, ovec[1]+1, off, re)
 end

base/shell.jl

@@ -53,7 +53,7 @@ function shell_parse(str::AbstractString, interpolate::Bool=true;
     while !done(s,j)
         c, k = next(s,j)
         if !in_single_quotes && !in_double_quotes && isspace(c)
-            update_arg(s[i:j-1])
+            update_arg(s[i:prevind(s, j)])
             append_arg()
             j = k
             while !done(s,j)
@@ -65,7 +65,7 @@ function shell_parse(str::AbstractString, interpolate::Bool=true;
                 j = k
             end
         elseif interpolate && !in_single_quotes && c == '$'
-            update_arg(s[i:j-1]); i = k; j = k
+            update_arg(s[i:prevind(s, j)]); i = k; j = k
             if done(s,k)
                 error("\$ right before end of command")
             end
@@ -79,24 +79,24 @@ function shell_parse(str::AbstractString, interpolate::Bool=true;
         else
             if !in_double_quotes && c == '\''
                 in_single_quotes = !in_single_quotes
-                update_arg(s[i:j-1]); i = k
+                update_arg(s[i:prevind(s, j)]); i = k
             elseif !in_single_quotes && c == '"'
                 in_double_quotes = !in_double_quotes
-                update_arg(s[i:j-1]); i = k
+                update_arg(s[i:prevind(s, j)]); i = k
             elseif c == '\\'
                 if in_double_quotes
                     if done(s,k)
                         error("unterminated double quote")
                     end
                     if s[k] == '"' || s[k] == '$' || s[k] == '\\'
-                        update_arg(s[i:j-1]); i = k
+                        update_arg(s[i:prevind(s, j)]); i = k
                         c, k = next(s,k)
                     end
                 elseif !in_single_quotes
                     if done(s,k)
                         error("dangling backslash")
                     end
-                    update_arg(s[i:j-1]); i = k
+                    update_arg(s[i:prevind(s, j)]); i = k
                     c, k = next(s,k)
                 end
             elseif !in_single_quotes && !in_double_quotes && c in special

base/strings/types.jl

@@ -4,32 +4,38 @@
 
 ## substrings reference original strings ##
 
+"""
+    SubString(s::AbstractString, i::Integer, j::Integer=endof(s))
+    SubString(s::AbstractString, r::UnitRange{<:Integer})
+
+Like [`getindex`](@ref), but returns a view into the parent string `s`
+within range `i:j` or `r` respectively instead of making a copy.
+"""
 struct SubString{T<:AbstractString} <: AbstractString
     string::T
     offset::Int
     endof::Int
 
     function SubString{T}(s::T, i::Int, j::Int) where T<:AbstractString
-        if i > endof(s) || j<i
-            return new(s, i-1, 0)
-        else
-            if !isvalid(s,i)
-                throw(ArgumentError("invalid SubString index"))
-            end
-
-            while !isvalid(s,j) && j > i
-                j -= 1
-            end
-
-            o = i-1
-            new(s, o, max(0, j-o))
-        end
+        i > j && return new(s, i - 1, 0) # always allow i > j as it is consistent with getindex
+        isvalid(s, i) || throw(BoundsError(s, i))
+        isvalid(s, j) || throw(BoundsError(s, j))
+        new(s, i-1, j-i+1)
     end
 end
+
 SubString(s::T, i::Int, j::Int) where {T<:AbstractString} = SubString{T}(s, i, j)
-SubString(s::SubString, i::Int, j::Int) = SubString(s.string, s.offset+i, s.offset+j)
-SubString(s::AbstractString, i::Integer, j::Integer) = SubString(s, Int(i), Int(j))
-SubString(s::AbstractString, i::Integer) = SubString(s, i, endof(s))
+SubString(s::AbstractString, i::Integer, j::Integer=endof(s)) = SubString(s, Int(i), Int(j))
+SubString(s::AbstractString, r::UnitRange{<:Integer}) = SubString(s, first(r), last(r))
+
+function SubString(s::SubString, i::Int, j::Int)
+    # always allow i > j as it is consistent with getindex
+    i > j && return SubString(s.string, s.offset + i, s.offset + j)
+    i >= 1 || throw(BoundsError(s, i))
+    j <= endof(s) || throw(BoundsError(s, j))
+    SubString(s.string, s.offset + i, s.offset + j)
+end
+
 SubString(s::AbstractString) = SubString(s, 1, endof(s))
 SubString{T}(s::T) where {T<:AbstractString} = SubString{T}(s, 1, endof(s))
 

base/strings/util.jl

@@ -79,7 +79,7 @@ julia> chop(a)
 "Marc"
 ```
 """
-chop(s::AbstractString) = SubString(s, 1, endof(s)-1)
+chop(s::AbstractString) = SubString(s, 1, prevind(s, endof(s)))
 
 """
     chomp(s::AbstractString)
@@ -96,17 +96,17 @@ function chomp(s::AbstractString)
     i = endof(s)
     (i < 1 || s[i] != '\n') && (return SubString(s, 1, i))
     j = prevind(s,i)
-    (j < 1 || s[j] != '\r') && (return SubString(s, 1, i-1))
-    return SubString(s, 1, j-1)
+    (j < 1 || s[j] != '\r') && (return SubString(s, 1, j))
+    return SubString(s, 1, prevind(s,j))
 end
 function chomp(s::String)
     i = endof(s)
     if i < 1 || codeunit(s,i) != 0x0a
         SubString(s, 1, i)
     elseif i < 2 || codeunit(s,i-1) != 0x0d
-        SubString(s, 1, i-1)
+        SubString(s, 1, prevind(s, i))
     else
-        SubString(s, 1, i-2)
+        SubString(s, 1, prevind(s, i-1))
     end
 end
 

test/regex.jl

@@ -47,3 +47,6 @@ end
 # Backcapture reference in substitution string
 @test replace("abcde", r"(..)(?P<byname>d)", s"\g<byname>xy\\\1") == "adxy\\bce"
 @test_throws ErrorException replace("a", r"(?P<x>)", s"\g<y>")
+
+# Proper unicode handling
+@test  match(r"∀∀", "∀x∀∀∀").match == "∀∀"

test/strings/basic.jl

@@ -121,12 +121,14 @@ end
     @test ""[10:9] == ""
     @test "hello"[10:9] == ""
     @test "hellø"[10:9] == ""
-    @test SubString("hello", 1, 6)[10:9] == ""
+    @test SubString("hello", 1, 5)[10:9] == ""
     @test SubString("hello", 1, 0)[10:9] == ""
-    @test SubString("hellø", 1, 6)[10:9] == ""
+    @test SubString("hellø", 1, 5)[10:9] == ""
     @test SubString("hellø", 1, 0)[10:9] == ""
-    @test SubString("", 1, 6)[10:9] == ""
     @test SubString("", 1, 0)[10:9] == ""
+
+    @test_throws BoundsError SubString("", 1, 6)
+    @test_throws BoundsError SubString("", 1, 1)
 end
 
 @testset "issue #22500 (using `get()` to index strings with default returns)" begin

test/strings/search.jl

@@ -29,7 +29,7 @@ end
 # @test_throws ErrorException in("foobar","bar")
 @test_throws BoundsError search(b"\x1\x2",0x1,0)
 @test rsearchindex(b"foo",b"o",0) == 0
-@test rsearchindex(SubString("",1,1),SubString("",1,1)) == 1
+@test rsearchindex(SubString("",1,0),SubString("",1,0)) == 1
 
 @test search(b"foo",'o') == 2
 @test rsearch(b"foo",'o') == 3

test/strings/types.jl

@@ -25,25 +25,53 @@ for i1 = 1:length(u8str2)
     end
 end
 
+# tests that SubString of a single multibyte `Char` string, like "∀" which takes 3 bytes
+# gives the same result as `getindex` (except that it is a veiw not a copy)
+for idx in 0:1
+    @test SubString("∀", 1, idx) == "∀"[1:idx]
+end
+
+# Substring provided with invalid end index throws BoundsError
+@test_throws BoundsError SubString("∀", 1, 2)
+@test_throws BoundsError SubString("∀", 1, 3)
+@test_throws BoundsError SubString("∀", 1, 4)
+
+# Substring provided with invalid start index throws BoundsError
+@test_throws BoundsError SubString("∀∀", 2:4)
+
+# tests for SubString of more than one multibyte `Char` string
+# we are consistent with `getindex` for `String`
+for idx in [0, 1, 4]
+    @test SubString("∀∀", 1, idx) == "∀∀"[1:idx]
+    @test SubString("∀∀", 4, idx) == "∀∀"[4:idx]
+end
+
+# second index beyond endof("∀∀")
+for idx in 5:8
+    @test_throws BoundsError SubString("∀∀", 1, idx)
+    @test_throws BoundsError SubString("∀∀", 4, idx)
+end
+
 let str="tempus fugit"              #length(str)==12
-    ss=SubString(str,1,length(str)) #match source string
+    ss=SubString(str,1,endof(str)) #match source string
+    @test length(ss)==length(str)
+
+    ss=SubString(str,1:endof(str))
     @test length(ss)==length(str)
 
     ss=SubString(str,1,0)    #empty SubString
     @test length(ss)==0
 
-    ss=SubString(str,14,20)  #start indexed beyond source string length
+    ss=SubString(str,1:0)
     @test length(ss)==0
 
-    ss=SubString(str,10,16)  #end indexed beyond source string length
-    @test length(ss)==3
+    @test_throws BoundsError SubString(str,14,20)  #start indexing beyond source string length
+    @test_throws BoundsError SubString(str,10,16)  #end indexing beyond source string length
 
-    str2=""
-    ss=SubString(str2,1,4)  #empty source string
-    @test length(ss)==0
-
-    ss=SubString(str2,1,1)  #empty source string, identical start and end index
-    @test length(ss)==0
+    @test_throws BoundsError SubString("", 1, 4)  #empty source string
+    @test_throws BoundsError SubString("", 1, 1)  #empty source string, identical start and end index
+    @test_throws BoundsError SubString("", 10, 12)
+    @test SubString("",12,10) == ""
 end
 
 @test SubString("foobar", big(1), big(3)) == "foo"
@@ -55,7 +83,7 @@ let str = "aa\u2200\u2222bb"
     write(b, u)
     @test String(take!(b)) == "\u2200\u2222"
 
-    @test_throws ArgumentError SubString(str, 4, 5)
+    @test_throws BoundsError SubString(str, 4, 5)
     @test_throws BoundsError next(u, 0)
     @test_throws BoundsError next(u, 7)
     @test_throws BoundsError getindex(u, 0)
@@ -68,21 +96,14 @@ let str = "aa\u2200\u2222bb"
 end
 
 let str = "føøbar"
+    @test_throws BoundsError SubString(str, 10, 10)
     u = SubString(str, 4, 3)
     @test length(u) == 0
     b = IOBuffer()
     write(b, u)
     @test String(take!(b)) == ""
 end
 
-let str = "føøbar"
-    u = SubString(str, 10, 10)
-    @test length(u) == 0
-    b = IOBuffer()
-    write(b, u)
-    @test String(take!(b)) == ""
-end
-
 # search and SubString (issue #5679)
 let str = "Hello, world!"
     u = SubString(str, 1, 5)
@@ -91,6 +112,22 @@ let str = "Hello, world!"
     @test rsearch(u, "ll") == 3:4
 end
 
+# SubString created from SubString
+let str = "Hello, world!"
+    u = SubString(str, 2, 5)
+    for idx in 1:4
+        @test SubString(u, 2, idx) == u[2:idx]
+        @test SubString(u, 2:idx) == u[2:idx]
+    end
+    @test_throws BoundsError SubString(u, 1, 10)
+    @test_throws BoundsError SubString(u, 1:10)
+    @test_throws BoundsError SubString(u, 20:30)
+    @test SubString(u, 20:15) == ""
+    @test_throws BoundsError SubString(u, -1:10)
+    @test SubString(u, -1, -10) == ""
+    @test SubString(SubString("123", 1, 2), -10, -20) == ""
+end
+
 # sizeof
 @test sizeof(SubString("abc\u2222def",4,4)) == 3
 
@@ -115,8 +152,8 @@ let ss, s="lorem ipsum",
                SubString(s,1,6)=>"lorem ",
                SubString(s,1,0)=>"",
                SubString(s,2,4)=>"ore",
-               SubString(s,2,16)=>"orem ipsum",
-               SubString(s,12,14)=>""
+               SubString(s,2,11)=>"orem ipsum",
+               SubString(s,15,14)=>""
                )
     for (ss,s) in sdict
         local ss
@@ -140,9 +177,18 @@ end #let
 
 #for isvalid(SubString{String})
 let s = "Σx + βz - 2"
-    for i in -1:(length(s) + 2)
-        local ss = SubString(s, 1, i)
-        @test isvalid(ss, i) == isvalid(s, i)
+    for i in -1:(length(s)+2)
+        if isvalid(s, i)
+            ss=SubString(s,1,i)
+            # make sure isvalid gives equivalent results for SubString and String
+            @test isvalid(ss,i)==isvalid(s,i)
+        else
+            if i > 0
+                @test_throws BoundsError SubString(s,1,i)
+            else
+                @test SubString(s,1,i) == ""
+            end
+        end
     end
 end
 

test/strings/util.jl

@@ -230,7 +230,11 @@ end
 
 @testset "chomp/chop" begin
     @test chomp("foo\n") == "foo"
+    @test chomp("fo∀\n") == "fo∀"
+    @test chomp("fo∀") == "fo∀"
     @test chop("fooε") == "foo"
+    @test chop("foεo") == "foε"
+    @test chop("∃∃∃∃") == "∃∃∃"
     @test isa(chomp("foo"), SubString)
     @test isa(chop("foo"), SubString)
 end