feat: exclude positions in Path:shorten (#268)

Author: l-kershaw

lua/plenary/path.lua

@@ -345,23 +345,49 @@ function Path:normalize(cwd)
   return _normalize_path(self.filename, self._cwd)
 end
 
-local function shorten_len(filename, len)
-  local final_match
+local function shorten_len(filename, len, exclude)
+  len = len or 1
+  exclude = exclude or { -1 }
+  local exc = {}
+
+  -- get parts in a table
+  local parts = {}
+  local empty_pos = {}
+  for m in (filename .. path.sep):gmatch("(.-)" .. path.sep) do
+    if m ~= "" then
+      parts[#parts + 1] = m
+    else
+      table.insert(empty_pos, #parts + 1)
+    end
+  end
+
+  for _, v in pairs(exclude) do
+    if v < 0 then
+      exc[v + #parts + 1] = true
+    else
+      exc[v] = true
+    end
+  end
+
   local final_path_components = {}
-  for match in (filename .. path.sep):gmatch("(.-)" .. path.sep) do
-    if #match > len then
+  local count = 1
+  for _, match in ipairs(parts) do
+    if not exc[count] and #match > len then
       table.insert(final_path_components, string.sub(match, 1, len))
     else
       table.insert(final_path_components, match)
     end
     table.insert(final_path_components, path.sep)
-    final_match = match
+    count = count + 1
   end
 
   local l = #final_path_components -- so that we don't need to keep calculating length
   table.remove(final_path_components, l) -- remove final slash
-  table.remove(final_path_components, l - 1) -- remvove shortened final component
-  table.insert(final_path_components, final_match) -- insert full final component
+
+  -- add back empty positions
+  for i = #empty_pos, 1, -1 do
+    table.insert(final_path_components, empty_pos[i], path.sep)
+  end
 
   return table.concat(final_path_components)
 end
@@ -388,10 +414,10 @@ local shorten = (function()
   end
 end)()
 
-function Path:shorten(len)
+function Path:shorten(len, exclude)
   assert(len ~= 0, "len must be at least 1")
-  if len and len > 1 then
-    return shorten_len(self.filename, len)
+  if (len and len > 1) or exclude ~= nil then
+    return shorten_len(self.filename, len, exclude)
   end
   return shorten(self.filename)
 end

tests/plenary/path_spec.lua

@@ -213,10 +213,8 @@ describe("Path", function()
       local short_path = Path:new(long_path):shorten()
       assert.are.same(short_path, "/t/i/a/l/path")
     end)
-  end)
 
-  describe(":shorten", function()
-    it("can shorten a path components to a given length", function()
+    it("can shorten a path's components to a given length", function()
       local long_path = "/this/is/a/long/path"
       local short_path = Path:new(long_path):shorten(2)
       assert.are.same(short_path, "/th/is/a/lo/path")
@@ -231,6 +229,41 @@ describe("Path", function()
       short_path = Path:new(long_path):shorten(5)
       assert.are.same(short_path, "this/is/an/extre/long/path")
     end)
+
+    it("can shorten a path's components when excluding parts", function()
+      local long_path = "/this/is/a/long/path"
+      local short_path = Path:new(long_path):shorten(nil, { 1, -1 })
+      assert.are.same(short_path, "/this/i/a/l/path")
+
+      -- without the leading /
+      long_path = "this/is/a/long/path"
+      short_path = Path:new(long_path):shorten(nil, { 1, -1 })
+      assert.are.same(short_path, "this/i/a/l/path")
+
+      -- where excluding positions greater than the number of parts
+      long_path = "this/is/an/extremely/long/path"
+      short_path = Path:new(long_path):shorten(nil, { 2, 4, 6, 8 })
+      assert.are.same(short_path, "t/is/a/extremely/l/path")
+
+      -- where excluding positions less than the negation of the number of parts
+      long_path = "this/is/an/extremely/long/path"
+      short_path = Path:new(long_path):shorten(nil, { -2, -4, -6, -8 })
+      assert.are.same(short_path, "this/i/an/e/long/p")
+    end)
+
+    it("can shorten a path's components to a given length and exclude positions", function()
+      local long_path = "/this/is/a/long/path"
+      local short_path = Path:new(long_path):shorten(2, { 1, -1 })
+      assert.are.same(short_path, "/this/is/a/lo/path")
+
+      long_path = "this/is/a/long/path"
+      short_path = Path:new(long_path):shorten(3, { 2, -2 })
+      assert.are.same(short_path, "thi/is/a/long/pat")
+
+      long_path = "this/is/an/extremely/long/path"
+      short_path = Path:new(long_path):shorten(5, { 3, -3 })
+      assert.are.same(short_path, "this/is/an/extremely/long/path")
+    end)
   end)
 
   describe("mkdir / rmdir", function()

tests/plenary/strings_spec.lua

@@ -78,7 +78,10 @@ describe("strings", function()
         args = { "アイウエオ", 10, nil, 1 },
         expected = { single = "アイウエオ", double = "アイウエオ" },
       },
-      { args = { "アイウエオ", 9, nil, -1 }, expected = { single = "…イウエオ", double = "…ウエオ" } },
+      {
+        args = { "アイウエオ", 9, nil, -1 },
+        expected = { single = "…イウエオ", double = "…ウエオ" },
+      },
       { args = { "アイウエオ", 8, nil, -1 }, expected = { single = "…ウエオ", double = "…ウエオ" } },
       { args = { "├─┤", 7, nil, -1 }, expected = { single = "├─┤", double = "├─┤" } },
       { args = { "├─┤", 6, nil, -1 }, expected = { single = "├─┤", double = "├─┤" } },