fix(vim.range): empty ranges semantics vs regular ranges #39474

Problem:
- Empty ranges have different `<`, `<=`, `has` and `intersect` semantics compared to regular ranges.
- `to_inclusive_pos` assumes that the end position of a range is exclusive, which is not true for empty ranges

Solution:
Special case empty ranges in these operations.

1 files changed, 83 insertions, 3 deletions

diff --git a/test/functional/lua/range_spec.lua b/test/functional/lua/range_spec.lua
index c47dc25363..bb2235d6c6 100644
--- a/test/functional/lua/range_spec.lua
+++ b/test/functional/lua/range_spec.lua
@@ -90,12 +90,92 @@ describe('vim.range', function()
     )
   end)
 
-  it('checks whether a range does not contain an empty range just outside it', function()
+  it('a range does not contain an empty range just outside it', function()
     eq(
       false,
       exec_lua(function()
-        local buf = vim.api.nvim_create_buf(false, true)
-        return vim.range(buf, 0, 0, 0, 4):has(vim.range(buf, 0, 0, 0, 0))
+        return vim.range(0, 0, 0, 0, 4):has(vim.range(0, 0, 0, 0, 0))
+      end)
+    )
+
+    eq(
+      false,
+      exec_lua(function()
+        return vim.range(0, 0, 0, 0, 4):has(vim.range(0, 0, 4, 0, 4))
+      end)
+    )
+  end)
+
+  it('an empty range contains no other range', function()
+    eq(
+      false,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0):has(vim.range(0, 1, 0, 1, 0))
+      end)
+    )
+    eq(
+      false,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0):has(vim.range(0, 1, 0, 2, 0))
+      end)
+    )
+    eq(
+      false,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0):has(vim.range(0, 0, 0, 1, 0))
+      end)
+    )
+  end)
+
+  it('an empty range intersercts with no other range', function()
+    eq(
+      nil,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0):intersect(vim.range(0, 1, 0, 1, 0))
+      end)
+    )
+    eq(
+      nil,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0):intersect(vim.range(0, 1, 0, 2, 0))
+      end)
+    )
+    eq(
+      nil,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0):intersect(vim.range(0, 0, 0, 1, 0))
+      end)
+    )
+  end)
+
+  it('empty range comparison semantics', function()
+    eq(
+      true,
+      exec_lua(function()
+        return vim.range(0, 0, 0, 0, 0) < vim.range(0, 0, 0, 0, 1)
+      end)
+    )
+
+    eq(
+      true,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 0) < vim.range(0, 1, 0, 1, 1)
+      end)
+    )
+
+    eq(
+      true,
+      exec_lua(function()
+        return vim.range(0, 1, 1, 1, 1) > vim.range(0, 1, 0, 1, 1)
+      end)
+    )
+  end)
+
+  it('1 byte wide range is not empty', function()
+    eq(
+      false,
+      exec_lua(function()
+        return vim.range(0, 1, 0, 1, 1):is_empty()
       end)
     )
   end)