fix(lua): ensure inspect_pos() only shows visible highlight extmarks

Problem:  Unpaired marks are shown with `filter.extmarks == true`, which
          should only return visible highlights. Misleading `end_col`
          included in `inspect_pos()` for unpaired mark; it is set to
          `start_col + 1` which would be a visible highlight, which it is
          not. Custom "is_here" filter used to get extmarks overlapping a
          position.

Solution: Exclude unpaired highlight extmarks with `filter.extmarks == true`.
          Set `end_col` to `start_col` for an unpaired mark. Supply
          appropriate arguments to nvim_buf_get_extmarks() to return
          overlapping extmarks; exclude marks whose end is at `{row, col}`
          with `filter.extmarks == true`.

2 files changed, 84 insertions, 34 deletions

diff --git a/runtime/lua/vim/_inspector.lua b/runtime/lua/vim/_inspector.lua
index 35063dffca..08dc2c5c78 100644
--- a/runtime/lua/vim/_inspector.lua
+++ b/runtime/lua/vim/_inspector.lua
@@ -104,30 +104,32 @@ function vim.inspect_pos(bufnr, row, col, filter)
 
   --- Convert an extmark tuple into a table
   local function to_map(extmark)
-    extmark = {
+    local opts = resolve_hl(extmark[4])
+    return {
       id = extmark[1],
       row = extmark[2],
       col = extmark[3],
-      opts = resolve_hl(extmark[4]),
+      end_row = opts.end_row or extmark[2],
+      end_col = opts.end_col or extmark[3],
+      opts = opts,
+      ns_id = opts.ns_id,
+      ns = nsmap[opts.ns_id] or '',
     }
-    extmark.ns_id = extmark.opts.ns_id
-    extmark.ns = nsmap[extmark.ns_id] or ''
-    extmark.end_row = extmark.opts.end_row or extmark.row -- inclusive
-    extmark.end_col = extmark.opts.end_col or (extmark.col + 1) -- exclusive
-    return extmark
   end
 
-  --- Check if an extmark overlaps this position
-  local function is_here(extmark)
-    return (row >= extmark.row and row <= extmark.end_row) -- within the rows of the extmark
-      and (row > extmark.row or col >= extmark.col) -- either not the first row, or in range of the col
-      and (row < extmark.end_row or col < extmark.end_col) -- either not in the last row or in range of the col
+  --- Exclude end_col and unpaired marks from the overlapping marks, unless
+  --- filter.extmarks == 'all' (a highlight is drawn until end_col - 1).
+  local function exclude_end_col(extmark)
+    return filter.extmarks == 'all' or row < extmark.end_row or col < extmark.end_col
   end
 
-  -- all extmarks at this position
-  local extmarks = vim.api.nvim_buf_get_extmarks(bufnr, -1, 0, -1, { details = true })
+  -- All overlapping extmarks at this position:
+  local extmarks = vim.api.nvim_buf_get_extmarks(bufnr, -1, { row, col }, { row, col }, {
+    details = true,
+    overlap = true,
+  })
   extmarks = vim.tbl_map(to_map, extmarks)
-  extmarks = vim.tbl_filter(is_here, extmarks)
+  extmarks = vim.tbl_filter(exclude_end_col, extmarks)
 
   if filter.semantic_tokens then
     results.semantic_tokens = vim.tbl_filter(function(extmark)
diff --git a/test/functional/lua/inspector_spec.lua b/test/functional/lua/inspector_spec.lua
index 89a103f51f..59b85874b1 100644
--- a/test/functional/lua/inspector_spec.lua
+++ b/test/functional/lua/inspector_spec.lua
@@ -12,23 +12,25 @@ describe('vim.inspect_pos', function()
   end)
 
   it('it returns items', function()
-    local buf, ns1, ns2, items, other_buf_syntax = exec_lua(function()
+    local buf, ns1, ns2 = exec_lua(function()
       local buf = vim.api.nvim_create_buf(true, false)
-      local buf1 = vim.api.nvim_create_buf(true, false)
+      _G.buf1 = vim.api.nvim_create_buf(true, false)
       local ns1 = vim.api.nvim_create_namespace('ns1')
       local ns2 = vim.api.nvim_create_namespace('')
       vim.api.nvim_set_current_buf(buf)
       vim.api.nvim_buf_set_lines(0, 0, -1, false, { 'local a = 123' })
-      vim.api.nvim_buf_set_lines(buf1, 0, -1, false, { '--commentline' })
+      vim.api.nvim_buf_set_lines(_G.buf1, 0, -1, false, { '--commentline' })
       vim.bo[buf].filetype = 'lua'
-      vim.bo[buf1].filetype = 'lua'
+      vim.bo[_G.buf1].filetype = 'lua'
       vim.api.nvim_buf_set_extmark(buf, ns1, 0, 10, { hl_group = 'Normal' })
-      vim.api.nvim_buf_set_extmark(buf, ns2, 0, 10, { hl_group = 'Normal' })
+      vim.api.nvim_buf_set_extmark(buf, ns1, 0, 10, { hl_group = 'Normal', end_col = 10 })
+      vim.api.nvim_buf_set_extmark(buf, ns2, 0, 10, { hl_group = 'Normal', end_col = 11 })
       vim.cmd('syntax on')
-      return buf, ns1, ns2, vim.inspect_pos(0, 0, 10), vim.inspect_pos(buf1, 0, 10).syntax
+      return buf, ns1, ns2
     end)
 
     eq('', eval('v:errmsg'))
+    -- Only visible highlights with `filter.extmarks == true`
     eq({
       buffer = buf,
       col = 10,
@@ -39,6 +41,37 @@ describe('vim.inspect_pos', function()
           end_col = 11,
           end_row = 0,
           id = 1,
+          ns = '',
+          ns_id = ns2,
+          opts = {
+            end_row = 0,
+            end_col = 11,
+            hl_eol = false,
+            hl_group = 'Normal',
+            hl_group_link = 'Normal',
+            ns_id = ns2,
+            priority = 4096,
+            right_gravity = true,
+            end_right_gravity = false,
+          },
+          row = 0,
+        },
+      },
+      treesitter = {},
+      semantic_tokens = {},
+      syntax = { { hl_group = 'luaNumber', hl_group_link = 'Constant' } },
+    }, exec_lua('return vim.inspect_pos(0, 0, 10)'))
+    -- All extmarks with `filters.extmarks == 'all'`
+    eq({
+      buffer = buf,
+      col = 10,
+      row = 0,
+      extmarks = {
+        {
+          col = 10,
+          end_col = 10,
+          end_row = 0,
+          id = 1,
           ns = 'ns1',
           ns_id = ns1,
           opts = {
@@ -59,32 +92,47 @@ describe('vim.inspect_pos', function()
           ns = '',
           ns_id = ns2,
           opts = {
+            end_row = 0,
+            end_col = 11,
             hl_eol = false,
             hl_group = 'Normal',
             hl_group_link = 'Normal',
             ns_id = ns2,
             priority = 4096,
             right_gravity = true,
+            end_right_gravity = false,
           },
           row = 0,
         },
-      },
-      treesitter = {},
-      semantic_tokens = {},
-      syntax = {
         {
-          hl_group = 'luaNumber',
-          hl_group_link = 'Constant',
+          col = 10,
+          end_col = 10,
+          end_row = 0,
+          id = 2,
+          ns = 'ns1',
+          ns_id = ns1,
+          opts = {
+            end_row = 0,
+            end_col = 10,
+            hl_eol = false,
+            hl_group = 'Normal',
+            hl_group_link = 'Normal',
+            ns_id = ns1,
+            priority = 4096,
+            right_gravity = true,
+            end_right_gravity = false,
+          },
+          row = 0,
         },
       },
-    }, items)
-
+      treesitter = {},
+      semantic_tokens = {},
+      syntax = { { hl_group = 'luaNumber', hl_group_link = 'Constant' } },
+    }, exec_lua('return vim.inspect_pos(0, 0, 10, { extmarks = "all" })'))
+    -- Syntax from other buffer.
     eq({
-      {
-        hl_group = 'luaComment',
-        hl_group_link = 'Comment',
-      },
-    }, other_buf_syntax)
+      { hl_group = 'luaComment', hl_group_link = 'Comment' },
+    }, exec_lua('return vim.inspect_pos(_G.buf1, 0, 10).syntax'))
   end)
 end)