fix(editline): format empty strings (#133)

If string to format is too small it will fail to format it.

Author: Tieske

spec/09-editline-format_spec.lua

@@ -393,6 +393,21 @@ describe("EditLine:", function()
       end)
 
 
+      it("formats an empty string", function()
+        line = EditLine(""):goto_index(0)
+        local result, row, col = testwrap({
+          width = 60,
+          first_width = 60,
+          wordwrap = false,
+          pad = false,
+          pad_last = false
+        })
+        assert.are.same({"|"}, result)
+        assert.are.equal(1, row)
+        assert.are.equal(1, col)
+      end)
+
+
       it("formats a string with padding", function()
         assert.are.same({
           'Hello, this is a simple 🚀 test string to check the formatti|',
@@ -726,6 +741,21 @@ describe("EditLine:", function()
       end)
 
 
+      it("formats an empty string", function()
+        line = EditLine(""):goto_index(0)
+        local result, row, col = testwrap({
+          width = 60,
+          first_width = 60,
+          wordwrap = true,
+          pad = false,
+          pad_last = false
+        })
+        assert.are.same({"|"}, result)
+        assert.are.equal(1, row)
+        assert.are.equal(1, col)
+      end)
+
+
       it("formats a string with padding", function()
         assert.are.same({
           'Hello, this is a simple 🚀 test string to check the |        ',

src/terminal/editline.lua

@@ -578,7 +578,15 @@ do
     self:goto_home()
 
     local size = #self.chars
-    while self.cursor_idx < size do
+    if size == 0 then
+      -- empty line, special case
+      lines[1] = EditLine("")
+      line_cols[1] = 0
+      cur_line = 1
+      cur_col = width - first_width + 1
+    end
+
+    while self.cursor_idx <= size do
       local line, cols = wrapper(self, target_size)
 -- print("line:", "'"..tostring(line).."'", cols)
       lines[#lines + 1] = line