xy_to_offset, offset_to_xy tweaks and tests

Note that the "one past the last byte" tests need
    JuliaLang/JuliaSyntax.jl#552 to pass

Author: mlechu

src/utils.jl

@@ -51,8 +51,7 @@ get_fileinfo(s::ServerState, t::TextDocumentIdentifier) = get_fileinfo(s, URI(t.
 """
 Convert 0-based `(;line = y, character = x)` to a 1-based byte offset
 """
-function xy_to_offset(fi::FileInfo, pos::Position)
-    code = fi.parsed_stream.textbuf
+function xy_to_offset(code::Vector{UInt8}, pos::Position)
     b = 0
     for z in 1:pos.line
         b = findnext(isequal(UInt8('\n')), code, b + 1)
@@ -66,12 +65,16 @@ function xy_to_offset(fi::FileInfo, pos::Position)
     end
     return b + line_b
 end
+xy_to_offset(fi::FileInfo, pos::Position) = xy_to_offset(fi.parsed_stream.textbuf, pos)
 
 """
 Convert a 1-based byte offset to a 0-based line and character number
 """
-function offset_to_xy(fi::FileInfo, b::Integer)
-    sf = JuliaSyntax.SourceFile(fi.parsed_stream)
+function offset_to_xy(ps::Union{AbstractString, JuliaSyntax.ParseStream}, b::Integer)
+    sf = JuliaSyntax.SourceFile(ps)
+    @assert b in JS.first_byte(ps):JS.last_byte(ps) + 1
     l, c = JuliaSyntax.source_location(sf, b)
     return Position(;line = l-1, character = c-1)
 end
+offset_to_xy(code::Vector{UInt8}, b::Integer) = offset_to_xy(String(copy(code)), b)
+offset_to_xy(fi::FileInfo, b::Integer) = offset_to_xy(fi.parsed_stream, b)

test/runtests.jl

@@ -2,4 +2,5 @@ using Test
 
 @testset "JETLS" begin
     @testset "basic" include("basic.jl")
+    @testset "utils" include("utils.jl")
 end

test/utils.jl

@@ -0,0 +1,36 @@
+using Test
+using JETLS
+
+fake_files = [
+"",
+"1",
+"\n\n\n",
+"""
+aaa
+b
+ccc
+Αα,Ββ,Γγ,Δδ,Εε,Ζζ,Ηη,Θθ,Ιι,Κκ,Λλ,Μμ,Νν,Ξξ,Οο,Ππ,Ρρ,Σσς,Ττ,Υυ,Φφ,Χχ,Ψψ,Ωω
+""",
+]
+
+function test_string_positions(s)
+    v = Vector{UInt8}(s)
+    for b in eachindex(s)
+        pos = JETLS.offset_to_xy(v, b)
+        b2 =  JETLS.xy_to_offset(v, pos)
+        @test b === b2
+    end
+    # One past the last byte is a valid position in an editor
+    b = length(v) + 1
+    pos = JETLS.offset_to_xy(v, b)
+    b2 =  JETLS.xy_to_offset(v, pos)
+    @test b === b2
+end
+
+@testset "Cursor file position <-> byte" begin
+    for i in eachindex(fake_files)
+        @testset "fake_files[$i]" begin
+            test_string_positions(fake_files[i])
+        end
+    end
+end