fix(path): Handle joining of empty strings (fixes #379)

Author: sindrets

lua/diffview/path.lua

@@ -317,8 +317,8 @@ function PathLib:join(...)
 
   for i = 1, table.maxn(segments) do
     local cur = segments[i]
-    if cur then
-      if i > 1 and not ret:sub(-1, -1):match("[\\/]") then
+    if cur and cur ~= "" then
+      if #ret > 0 and not ret:sub(-1, -1):match("[\\/]") then
         ret = ret .. self.sep
       end
       ret = ret .. cur

tests/functional/pathlib_spec.lua

@@ -266,6 +266,7 @@ describe("diffview.path", function()
       eq([[/foo/bar/baz]], pl:join({ "/", "foo", "bar", "baz" }))
       eq([[/foo/bar/baz]], pl:join({ "/foo/bar", "baz" }))
       eq([[/foo/bar/baz]], pl:join({ "/", "foo/", "/bar///", "/baz" }))
+      eq([[foo/bar/baz]], pl:join({ "", "foo", "bar", "baz" }))
     end)
 
     it("works for Windows paths", function()
@@ -275,6 +276,7 @@ describe("diffview.path", function()
       eq([[C:\foo\bar\baz]], pl:join({ "C:\\foo\\bar", "baz" }))
       eq([[C:\foo\bar\baz]], pl:join({ "C:\\", "foo\\", "\\bar\\\\", "\\baz" }))
       eq([[\foo\bar\baz]], pl:join({ "\\", "foo", "bar", "baz" }))
+      eq([[foo\bar\baz]], pl:join({ "", "foo", "bar", "baz" }))
 
       eq([[\\foo\bar\baz]], pl:join({ [[\\]], "foo", "bar", "baz" }))
       eq([[\\foo\bar\baz]], pl:join({ [[\\foo\\bar]], "baz" }))