fix on_change when text changes back to original

Author: jrop

lua/morph.lua

@@ -74,6 +74,7 @@ local H = {}
 --- @field attributes morph.TagAttributes
 --- @field children morph.Tree
 --- @field private ctx? morph.Ctx
+--- @field private curr_text? string
 
 --- An element is an instantiated Tag
 --- @class morph.Element : morph.Tag
@@ -350,6 +351,9 @@ Morph.__index = Morph
 ---   on_tag?: fun(tag: morph.Tag, start0: morph.Pos00, stop0: morph.Pos00): any
 --- }
 function Morph.markup_to_lines(opts)
+  --- @type (fun(s: string))[]
+  local listeners = {}
+
   --- @type string[]
   local lines = {}
 
@@ -359,11 +363,17 @@ function Morph.markup_to_lines(opts)
   local function put(s)
     lines[curr_line1] = (lines[curr_line1] or '') .. s
     curr_col1 = #lines[curr_line1] + 1
+    for _, listener in ipairs(listeners) do
+      listener(s)
+    end
   end
   local function put_line()
     table.insert(lines, '')
     curr_line1 = curr_line1 + 1
     curr_col1 = 1
+    for _, listener in ipairs(listeners) do
+      listener '\n'
+    end
   end
 
   --- @param node morph.Tree
@@ -382,9 +392,13 @@ function Morph.markup_to_lines(opts)
         end
       end,
       tag = function(t)
+        local curr_text = ''
+        listeners[#listeners + 1] = function(s) curr_text = curr_text .. s end
         local start0 = Pos00.new(curr_line1 - 1, curr_col1 - 1)
         visit(t.children)
         local stop0 = Pos00.new(curr_line1 - 1, curr_col1 - 1)
+        table.remove(listeners, #listeners)
+        t.curr_text = curr_text
 
         if opts.on_tag then opts.on_tag(t, start0, stop0) end
       end,
@@ -917,10 +931,10 @@ function Morph:_on_text_changed()
       -- Just because extmarks have shifted, doesn't mean their text has changed:
       -- Lookup the old value vs the new on and check:
       local cached_tag = assert(self.text_content.curr.extmark_ids_to_tag[cached_extmark.id])
-      local cached_tag_text = Morph.markup_to_string { tree = cached_tag }
       local curr_text = live_extmark:_text()
 
-      if cached_tag_text ~= curr_text then
+      if cached_tag.curr_text ~= curr_text then
+        cached_tag.curr_text = curr_text
         table.insert(changed, { extmark = live_extmark, text = curr_text })
       end
     end

spec/morph_spec.lua

@@ -1235,4 +1235,42 @@ describe('Morph', function()
       assert.are.same(captured_changed_text, '')
     end)
   end)
+
+  it('should recognize a text-change when text changes back to original content', function()
+    with_buf({}, function()
+      local captured_changed_text = ''
+
+      -- Text:
+      -- 01234
+      -- hello
+      --- @param ctx morph.Ctx
+      local function App(ctx)
+        return {
+          h('text', {
+            id = 'the-id',
+            on_change = function(e)
+              e.bubble_up = false
+              captured_changed_text = e.text
+            end,
+          }, { 'hello' }),
+        }
+      end
+      local r = Morph.new()
+      r:mount(h(App))
+
+      assert.are.same(get_text(), 'hello')
+
+      -- Delete the trailing 'o':
+      vim.api.nvim_buf_set_text(0, 0, 4, 0, 5, {})
+      assert.are.same(get_text(), 'hell')
+      r:_on_text_changed()
+      assert.are.same(captured_changed_text, 'hell')
+
+      -- Reinsert the trailing 'o':
+      vim.api.nvim_buf_set_text(0, 0, 4, 0, 4, { 'o' })
+      assert.are.same(get_text(), 'hello')
+      r:_on_text_changed()
+      assert.are.same(captured_changed_text, 'hello')
+    end)
+  end)
 end)