feat: fill missing levels in heading sections calculation with 0

## Details

Previously when calculating sections for the following input:

```
## Notice
# Section A
### Note
# Section B
```

The results would be:

```
## Notice -> { 1 }
# Section A -> { 2 }
### Note -> { 2, 1 }
# Section B -> { 3 }
```

This change updates the calculation to always produce a number of
sections equal to the current heading level and to compute the nesting
level based off of sibling sections at the same level only. Any levels
that are skipped are filled in with 0s.

So now the results would be:

```
## Notice -> { 0, 1 }
# Section A -> { 1 }
### Note -> { 1, 0, 1 }
# Section B -> { 2 }
```

Author: MeanderingProgrammer

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '7.8.4'
+M.version = '7.8.5'
 
 function M.check()
     M.start('version')

lua/render-markdown/lib/node.lua

@@ -27,6 +27,13 @@ function Node.new(buf, node)
     return self
 end
 
+---@private
+---@param node TSNode
+---@return render.md.Node
+function Node:create(node)
+    return Node.new(self.buf, node)
+end
+
 ---@param a render.md.Node
 ---@param b render.md.Node
 ---@return boolean
@@ -50,18 +57,23 @@ end
 
 ---@return integer[]
 function Node:sections()
-    local result, section = {}, self:parent('section')
+    local result, levels, section = {}, 0, self:parent('section')
     while section ~= nil do
-        local count = section:sibling_count('section')
-        table.insert(result, 1, count)
+        local level = section:level(false)
+        result[level] = section:sibling_count('section', level)
+        levels = math.max(levels, level)
         section = section:parent('section')
     end
+    -- Fill in any heading level gaps with 0
+    for i = 1, levels do
+        result[i] = result[i] or 0
+    end
     return result
 end
 
 ---@param parent boolean
 ---@return integer
-function Node:heading_level(parent)
+function Node:level(parent)
     local section = not parent and self or self:parent('section')
     if section == nil then
         return 0
@@ -84,7 +96,7 @@ function Node:level_in_section(target)
         end
         parent = parent:parent()
     end
-    return level, root ~= nil and Node.new(self.buf, root) or nil
+    return level, root ~= nil and self:create(root) or nil
 end
 
 ---@param target string
@@ -93,7 +105,7 @@ function Node:parent(target)
     local parent = self.node:parent()
     while parent ~= nil do
         if parent:type() == target then
-            return Node.new(self.buf, parent)
+            return self:create(parent)
         end
         parent = parent:parent()
     end
@@ -106,18 +118,23 @@ function Node:sibling(target)
     local sibling = self.node:next_sibling()
     while sibling ~= nil do
         if sibling:type() == target then
-            return Node.new(self.buf, sibling)
+            return self:create(sibling)
         end
         sibling = sibling:next_sibling()
     end
     return nil
 end
 
 ---@param target string
+---@param level? integer
 ---@return integer
-function Node:sibling_count(target)
+function Node:sibling_count(target, level)
     local count, sibling = 1, self.node:prev_sibling()
-    while sibling ~= nil and sibling:type() == target do
+    while
+        sibling ~= nil
+        and sibling:type() == target
+        and (level == nil or self:create(sibling):level(false) == level)
+    do
         count = count + 1
         sibling = sibling:prev_sibling()
     end
@@ -128,7 +145,7 @@ end
 ---@return render.md.Node?
 function Node:child_at(index)
     local node = self.node:named_child(index)
-    return node ~= nil and Node.new(self.buf, node) or nil
+    return node ~= nil and self:create(node) or nil
 end
 
 ---@param target_type string
@@ -138,7 +155,7 @@ function Node:child(target_type, target_row)
     for child in self.node:iter_children() do
         if child:type() == target_type then
             if target_row == nil or child:range() == target_row then
-                return Node.new(self.buf, child)
+                return self:create(child)
             end
         end
     end
@@ -148,7 +165,7 @@ end
 ---@param callback fun(node: render.md.Node)
 function Node:for_each_child(callback)
     for child in self.node:iter_children() do
-        callback(Node.new(self.buf, child))
+        callback(self:create(child))
     end
 end
 

lua/render-markdown/render/base.lua

@@ -97,10 +97,10 @@ function Base:indent(level)
         return 0
     end
     if level == nil then
-        level = self.node:heading_level(true)
+        level = self.node:level(true)
     elseif indent.skip_heading then
         local parent = self.node:parent('section')
-        level = parent ~= nil and parent:heading_level(true) or 0
+        level = parent ~= nil and parent:level(true) or 0
     end
     level = level - indent.skip_level
     if level <= 0 then

lua/render-markdown/render/section.lua

@@ -14,8 +14,8 @@ function Render:setup()
         return false
     end
 
-    local current_level = self.node:heading_level(false)
-    local parent_level = math.max(self.node:heading_level(true), self.indent.skip_level)
+    local current_level = self.node:level(false)
+    local parent_level = math.max(self.node:level(true), self.indent.skip_level)
     self.level_change = current_level - parent_level
 
     -- Nothing to do if there is not a change in level