test: make {MATCH:} behave less unexpectedly in screen:expect()

Include the rest of the line and allow multiple {MATCH:} patterns.

test/functional/ui/screen.lua

@@ -75,6 +75,7 @@ local busted = require('busted')
 local deepcopy = helpers.deepcopy
 local shallowcopy = helpers.shallowcopy
 local concat_tables = helpers.concat_tables
+local pesc = helpers.pesc
 local run_session = helpers.run_session
 local eq = helpers.eq
 local dedent = helpers.dedent
@@ -257,7 +258,7 @@ local ext_keys = {
 -- grid:        Expected screen state (string). Each line represents a screen
 --              row. Last character of each row (typically "|") is stripped.
 --              Common indentation is stripped.
---              "{MATCH:x}|" lines are matched against Lua pattern `x`.
+--              "{MATCH:x}" in a line is matched against Lua pattern `x`.
 -- attr_ids:    Expected text attributes. Screen rows are transformed according
 --              to this table, as follows: each substring S composed of
 --              characters having the same attributes will be substituted by
@@ -382,8 +383,20 @@ function Screen:expect(expected, attr_ids, ...)
       end
       for i, row in ipairs(expected_rows) do
         msg_expected_rows[i] = row
-        local m = (row ~= actual_rows[i] and row:match('{MATCH:(.*)}') or nil)
-        if row ~= actual_rows[i] and (not m or not (actual_rows[i] and actual_rows[i]:match(m))) then
+        local pat = nil
+        if actual_rows[i] and row ~= actual_rows[i] then
+          local after = row
+          while true do
+            local s, e, m = after:find('{MATCH:(.-)}')
+            if not s then
+              pat = pat and (pat .. pesc(after))
+              break
+            end
+            pat = (pat or '') .. pesc(after:sub(1, s - 1)) .. m
+            after = after:sub(e + 1)
+          end
+        end
+        if row ~= actual_rows[i] and (not pat or not actual_rows[i]:match(pat)) then
           msg_expected_rows[i] = '*' .. msg_expected_rows[i]
           if i <= #actual_rows then
             actual_rows[i] = '*' .. actual_rows[i]