2 files changed, 83 insertions, 1 deletions
diff --git a/lua/mason-core/path.lua b/lua/mason-core/path.lua
index 9eeed3ba..66f0f964 100644
--- a/lua/mason-core/path.lua
+++ b/lua/mason-core/path.lua
@@ -24,7 +24,38 @@ end
 ---@path root_path string
 ---@path path string
 function M.is_subdirectory(root_path, path)
-    return root_path == path or path:sub(1, #root_path + 1) == root_path .. sep
+    local root_path_normalized = vim.fs.normalize(root_path)
+    local path_normalized = vim.fs.normalize(path)
+    if path_normalized == root_path_normalized then
+        return true
+    end
+    for dir in vim.fs.parents(path_normalized) do
+        if root_path_normalized == dir then
+            return true
+        end
+    end
+    return false
+end
+
+local function find_closest_common_parent(from, to)
+    local distance = 0
+    for parent in vim.fs.parents(from) do
+        if to:find(parent, 1, true) then
+            return parent, distance
+        else
+            distance = distance + 1
+        end
+    end
+    return "/", distance
+end
+
+function M.relative(from, to)
+    local from_normalized = vim.fs.normalize(from)
+    local to_normalized = vim.fs.normalize(to)
+
+    local common_parent, distance = find_closest_common_parent(from_normalized, to_normalized)
+    local relative_path_component = distance == 0 and "." or (".."):rep(distance, "/")
+    return vim.fs.joinpath(relative_path_component, to_normalized:sub(#common_parent + 1))
 end
 
 return M
diff --git a/tests/mason-core/path_spec.lua b/tests/mason-core/path_spec.lua
index 3d0c2e25..4aeb48f1 100644
--- a/tests/mason-core/path_spec.lua
+++ b/tests/mason-core/path_spec.lua
@@ -22,4 +22,55 @@ describe("path", function()
         assert.is_false(path.is_subdirectory("/foo/bar", "/foo/bas/baz"))
         assert.is_false(path.is_subdirectory("/foo/bar", "/foo/bars/baz"))
     end)
+
+    describe("relative ::", function()
+        local matrix = {
+            {
+                from = "/home/user/dir1/fileA",
+                to = "/home/user/dir1/fileB",
+                expected = "./fileB",
+            },
+            {
+                from = "/home/user/dir1/fileA",
+                to = "/home/user/dir2/fileC",
+                expected = "../dir2/fileC",
+            },
+            {
+                from = "/home/user/dir1/subdir/fileD",
+                to = "/home/user/dir1/fileE",
+                expected = "../fileE",
+            },
+            {
+                from = "/home/user/dir1/subdir/fileD",
+                to = "/home/user/dir1/subdir/fileF",
+                expected = "./fileF",
+            },
+            {
+                from = "/home/user/dir1/fileG",
+                to = "/home/user/dir2/subdir/fileH",
+                expected = "../dir2/subdir/fileH",
+            },
+            {
+                from = "/home/user/dir1/subdir1/subdir2/fileI",
+                to = "/home/user/dir1/fileJ",
+                expected = "../../fileJ",
+            },
+            {
+                from = "/fileK",
+                to = "/home/fileL",
+                expected = "./home/fileL",
+            },
+            {
+                from = "/home/user/fileM",
+                to = "/home/user/dir1/dir2/fileL",
+                expected = "./dir1/dir2/fileL",
+            },
+        }
+
+        for _, test_case in ipairs(matrix) do
+            it(("should resolve from %s to %s: %s"):format(test_case.from, test_case.to, test_case.expected), function()
+                assert.equals(test_case.expected, path.relative(test_case.from, test_case.to))
+            end)
+        end
+    end)
 end)