vim-patch:8.2.3751: cannot assign a lambda to an option that takes a function

Problem:    Cannot assign a lambda to an option that takes a function.
Solution:   Automatically convert the lambda to a string. (Yegappan
            Lakshmanan, closes vim/vim#9286)

https://github.com/vim/vim/commit/6409553b6e3b4de4e1d72b8ee5445595214581ff

Co-authored-by: Yegappan Lakshmanan <yegappan@yahoo.com>

2 files changed, 230 insertions, 18 deletions

diff --git a/src/nvim/testdir/test_ins_complete.vim b/src/nvim/testdir/test_ins_complete.vim
index 0478ad1516..8b5f9a189f 100644
--- a/src/nvim/testdir/test_ins_complete.vim
+++ b/src/nvim/testdir/test_ins_complete.vim
@@ -1302,13 +1302,22 @@ func Test_completefunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn = function('MycompleteFunc1')
+  let &completefunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MycompleteFunc1_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MycompleteFunc1_args)
+  bw!
+
+  " Using string(funcref_variable) to set 'completefunc'
+  let Fn = function('MycompleteFunc1')
   let &completefunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MycompleteFunc1_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MycompleteFunc1_args)
-  call assert_fails('let &completefunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1326,13 +1335,22 @@ func Test_completefunc_callback()
 
   " Using a funcref variable to set 'completefunc'
   let Fn = funcref('MycompleteFunc2')
+  let &completefunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MycompleteFunc2_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MycompleteFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'completefunc'
+  let Fn = funcref('MycompleteFunc2')
   let &completefunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MycompleteFunc2_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MycompleteFunc2_args)
-  call assert_fails('let &completefunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -1349,6 +1367,15 @@ func Test_completefunc_callback()
   bw!
 
   " Set 'completefunc' to a lambda expression
+  let &completefunc = {a, b -> MycompleteFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MycompleteFunc3_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MycompleteFunc3_args)
+  bw!
+
+  " Set 'completefunc' to string(lambda_expression)
   let &completefunc = '{a, b -> MycompleteFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -1359,18 +1386,27 @@ func Test_completefunc_callback()
 
   " Set 'completefunc' to a variable with a lambda expression
   let Lambda = {a, b -> MycompleteFunc3(a, b)}
+  let &completefunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MycompleteFunc3_args = []
+  call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MycompleteFunc3_args)
+  bw!
+
+  " Set 'completefunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MycompleteFunc3(a, b)}
   let &completefunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MycompleteFunc3_args = []
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MycompleteFunc3_args)
-  call assert_fails('let &completefunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &completefunc = string(Lambda)
+  let &completefunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
@@ -1382,7 +1418,7 @@ func Test_completefunc_callback()
 
   call assert_fails("set completefunc=function('abc')", "E700:")
   call assert_fails("set completefunc=funcref('abc')", "E700:")
-  let &completefunc = "{a -> 'abc'}"
+  let &completefunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
 
   " Vim9 tests
@@ -1407,6 +1443,15 @@ func Test_completefunc_callback()
       add(g:LambdaComplete1_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &completefunc = (a, b) => LambdaComplete1(a, b)
+    new | only
+    setline(1, 'two')
+    g:LambdaComplete1_args = []
+    feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:LambdaComplete1_args)
+    bw!
+
+    # Test for using a string(lambda)
     &completefunc = '(a, b) => LambdaComplete1(a, b)'
     new | only
     setline(1, 'two')
@@ -1420,6 +1465,15 @@ func Test_completefunc_callback()
             add(g:LambdaComplete2_args, [findstart, base])
             return findstart ? 0 : []
         }
+    &completefunc = Fn
+    new | only
+    setline(1, 'three')
+    g:LambdaComplete2_args = []
+    feedkeys("A\<C-X>\<C-U>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:LambdaComplete2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &completefunc = string(Fn)
     new | only
     setline(1, 'three')
@@ -1462,13 +1516,22 @@ func Test_omnifunc_callback()
 
   " Using a funcref variable to set 'omnifunc'
   let Fn = function('MyomniFunc1')
+  let &omnifunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MyomniFunc1_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MyomniFunc1_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'omnifunc'
+  let Fn = function('MyomniFunc1')
   let &omnifunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MyomniFunc1_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MyomniFunc1_args)
-  call assert_fails('let &omnifunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1486,13 +1549,22 @@ func Test_omnifunc_callback()
 
   " Using a funcref variable to set 'omnifunc'
   let Fn = funcref('MyomniFunc2')
+  let &omnifunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MyomniFunc2_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MyomniFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'omnifunc'
+  let Fn = funcref('MyomniFunc2')
   let &omnifunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MyomniFunc2_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MyomniFunc2_args)
-  call assert_fails('let &omnifunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -1509,6 +1581,15 @@ func Test_omnifunc_callback()
   bw!
 
   " Set 'omnifunc' to a lambda expression
+  let &omnifunc = {a, b -> MyomniFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MyomniFunc3_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MyomniFunc3_args)
+  bw!
+
+  " Set 'omnifunc' to a string(lambda_expression)
   let &omnifunc = '{a, b -> MyomniFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -1519,18 +1600,27 @@ func Test_omnifunc_callback()
 
   " Set 'omnifunc' to a variable with a lambda expression
   let Lambda = {a, b -> MyomniFunc3(a, b)}
+  let &omnifunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MyomniFunc3_args = []
+  call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MyomniFunc3_args)
+  bw!
+
+  " Set 'omnifunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MyomniFunc3(a, b)}
   let &omnifunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MyomniFunc3_args = []
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MyomniFunc3_args)
-  call assert_fails('let &omnifunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &omnifunc = string(Lambda)
+  let &omnifunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
@@ -1542,7 +1632,7 @@ func Test_omnifunc_callback()
 
   call assert_fails("set omnifunc=function('abc')", "E700:")
   call assert_fails("set omnifunc=funcref('abc')", "E700:")
-  let &omnifunc = "{a -> 'abc'}"
+  let &omnifunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
 
   " Vim9 tests
@@ -1567,6 +1657,15 @@ func Test_omnifunc_callback()
       add(g:MyomniFunc2_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &omnifunc = (a, b) => MyomniFunc2(a, b)
+    new | only
+    setline(1, 'two')
+    g:MyomniFunc2_args = []
+    feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:MyomniFunc2_args)
+    bw!
+
+    # Test for using a string(lambda)
     &omnifunc = '(a, b) => MyomniFunc2(a, b)'
     new | only
     setline(1, 'two')
@@ -1577,6 +1676,15 @@ func Test_omnifunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b) => MyomniFunc2(a, b)
+    &omnifunc = Fn
+    new | only
+    setline(1, 'three')
+    g:MyomniFunc2_args = []
+    feedkeys("A\<C-X>\<C-O>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:MyomniFunc2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &omnifunc = string(Fn)
     new | only
     setline(1, 'three')
@@ -1619,13 +1727,22 @@ func Test_thesaurusfunc_callback()
 
   " Using a funcref variable to set 'thesaurusfunc'
   let Fn = function('MytsrFunc1')
+  let &thesaurusfunc = Fn
+  new | only
+  call setline(1, 'two')
+  let g:MytsrFunc1_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'two']], g:MytsrFunc1_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'thesaurusfunc'
+  let Fn = function('MytsrFunc1')
   let &thesaurusfunc = string(Fn)
   new | only
   call setline(1, 'two')
   let g:MytsrFunc1_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'two']], g:MytsrFunc1_args)
-  call assert_fails('let &thesaurusfunc = Fn', 'E729:')
   bw!
 
   " Test for using a funcref()
@@ -1643,13 +1760,22 @@ func Test_thesaurusfunc_callback()
 
   " Using a funcref variable to set 'thesaurusfunc'
   let Fn = funcref('MytsrFunc2')
+  let &thesaurusfunc = Fn
+  new | only
+  call setline(1, 'four')
+  let g:MytsrFunc2_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'four']], g:MytsrFunc2_args)
+  bw!
+
+  " Using a string(funcref_variable) to set 'thesaurusfunc'
+  let Fn = funcref('MytsrFunc2')
   let &thesaurusfunc = string(Fn)
   new | only
   call setline(1, 'four')
   let g:MytsrFunc2_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'four']], g:MytsrFunc2_args)
-  call assert_fails('let &thesaurusfunc = Fn', 'E729:')
   bw!
 
   " Test for using a lambda function
@@ -1666,6 +1792,15 @@ func Test_thesaurusfunc_callback()
   bw!
 
   " Set 'thesaurusfunc' to a lambda expression
+  let &thesaurusfunc = {a, b -> MytsrFunc3(a, b)}
+  new | only
+  call setline(1, 'six')
+  let g:MytsrFunc3_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'six']], g:MytsrFunc3_args)
+  bw!
+
+  " Set 'thesaurusfunc' to a string(lambda expression)
   let &thesaurusfunc = '{a, b -> MytsrFunc3(a, b)}'
   new | only
   call setline(1, 'six')
@@ -1676,18 +1811,27 @@ func Test_thesaurusfunc_callback()
 
   " Set 'thesaurusfunc' to a variable with a lambda expression
   let Lambda = {a, b -> MytsrFunc3(a, b)}
+  let &thesaurusfunc = Lambda
+  new | only
+  call setline(1, 'seven')
+  let g:MytsrFunc3_args = []
+  call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+  call assert_equal([[1, ''], [0, 'seven']], g:MytsrFunc3_args)
+  bw!
+
+  " Set 'thesaurusfunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b -> MytsrFunc3(a, b)}
   let &thesaurusfunc = string(Lambda)
   new | only
   call setline(1, 'seven')
   let g:MytsrFunc3_args = []
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
   call assert_equal([[1, ''], [0, 'seven']], g:MytsrFunc3_args)
-  call assert_fails('let &thesaurusfunc = Lambda', 'E729:')
   bw!
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
-  let &thesaurusfunc = string(Lambda)
+  let &thesaurusfunc = Lambda
   new | only
   call setline(1, 'eight')
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
@@ -1699,7 +1843,7 @@ func Test_thesaurusfunc_callback()
 
   call assert_fails("set thesaurusfunc=function('abc')", "E700:")
   call assert_fails("set thesaurusfunc=funcref('abc')", "E700:")
-  let &thesaurusfunc = "{a -> 'abc'}"
+  let &thesaurusfunc = {a -> 'abc'}
   call feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
 
   " Vim9 tests
@@ -1724,6 +1868,15 @@ func Test_thesaurusfunc_callback()
       add(g:MytsrFunc2_args, [findstart, base])
       return findstart ? 0 : []
     enddef
+    &thesaurusfunc = (a, b) => MytsrFunc2(a, b)
+    new | only
+    setline(1, 'two')
+    g:MytsrFunc2_args = []
+    feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'two']], g:MytsrFunc2_args)
+    bw!
+
+    # Test for using a string(lambda)
     &thesaurusfunc = '(a, b) => MytsrFunc2(a, b)'
     new | only
     setline(1, 'two')
@@ -1734,6 +1887,15 @@ func Test_thesaurusfunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b) => MytsrFunc2(a, b)
+    &thesaurusfunc = Fn
+    new | only
+    setline(1, 'three')
+    g:MytsrFunc2_args = []
+    feedkeys("A\<C-X>\<C-T>\<Esc>", 'x')
+    assert_equal([[1, ''], [0, 'three']], g:MytsrFunc2_args)
+    bw!
+
+    # Test for using a string(variable with a lambda expression)
     &thesaurusfunc = string(Fn)
     new | only
     setline(1, 'three')
diff --git a/src/nvim/testdir/test_tagfunc.vim b/src/nvim/testdir/test_tagfunc.vim
index 8690e30e77..06d074c261 100644
--- a/src/nvim/testdir/test_tagfunc.vim
+++ b/src/nvim/testdir/test_tagfunc.vim
@@ -138,12 +138,19 @@ func Test_tagfunc_callback()
 
   " Using a funcref variable to set 'tagfunc'
   let Fn = function('MytagFunc1')
+  let &tagfunc = Fn
+  new | only
+  let g:MytagFunc1_args = []
+  call assert_fails('tag a12', 'E433:')
+  call assert_equal(['a12', '', {}], g:MytagFunc1_args)
+
+  " Using a string(funcref_variable) to set 'tagfunc'
+  let Fn = function('MytagFunc1')
   let &tagfunc = string(Fn)
   new | only
   let g:MytagFunc1_args = []
   call assert_fails('tag a12', 'E433:')
   call assert_equal(['a12', '', {}], g:MytagFunc1_args)
-  call assert_fails('let &tagfunc = Fn', 'E729:')
 
   " Test for using a funcref()
   func MytagFunc2(pat, flags, info)
@@ -158,12 +165,19 @@ func Test_tagfunc_callback()
 
   " Using a funcref variable to set 'tagfunc'
   let Fn = funcref('MytagFunc2')
+  let &tagfunc = Fn
+  new | only
+  let g:MytagFunc2_args = []
+  call assert_fails('tag a14', 'E433:')
+  call assert_equal(['a14', '', {}], g:MytagFunc2_args)
+
+  " Using a string(funcref_variable) to set 'tagfunc'
+  let Fn = funcref('MytagFunc2')
   let &tagfunc = string(Fn)
   new | only
   let g:MytagFunc2_args = []
   call assert_fails('tag a14', 'E433:')
   call assert_equal(['a14', '', {}], g:MytagFunc2_args)
-  call assert_fails('let &tagfunc = Fn', 'E729:')
 
   " Test for using a script local function
   set tagfunc=<SID>ScriptLocalTagFunc
@@ -174,6 +188,14 @@ func Test_tagfunc_callback()
 
   " Test for using a script local funcref variable
   let Fn = function("s:ScriptLocalTagFunc")
+  let &tagfunc= Fn
+  new | only
+  let g:ScriptLocalFuncArgs = []
+  call assert_fails('tag a16', 'E433:')
+  call assert_equal(['a16', '', {}], g:ScriptLocalFuncArgs)
+
+  " Test for using a string(script local funcref variable)
+  let Fn = function("s:ScriptLocalTagFunc")
   let &tagfunc= string(Fn)
   new | only
   let g:ScriptLocalFuncArgs = []
@@ -192,6 +214,13 @@ func Test_tagfunc_callback()
   call assert_equal(['a17', '', {}], g:MytagFunc3_args)
 
   " Set 'tagfunc' to a lambda expression
+  let &tagfunc = {a, b, c -> MytagFunc3(a, b, c)}
+  new | only
+  let g:MytagFunc3_args = []
+  call assert_fails('tag a18', 'E433:')
+  call assert_equal(['a18', '', {}], g:MytagFunc3_args)
+
+  " Set 'tagfunc' to a string(lambda expression)
   let &tagfunc = '{a, b, c -> MytagFunc3(a, b, c)}'
   new | only
   let g:MytagFunc3_args = []
@@ -200,12 +229,19 @@ func Test_tagfunc_callback()
 
   " Set 'tagfunc' to a variable with a lambda expression
   let Lambda = {a, b, c -> MytagFunc3(a, b, c)}
+  let &tagfunc = Lambda
+  new | only
+  let g:MytagFunc3_args = []
+  call assert_fails("tag a19", "E433:")
+  call assert_equal(['a19', '', {}], g:MytagFunc3_args)
+
+  " Set 'tagfunc' to a string(variable with a lambda expression)
+  let Lambda = {a, b, c -> MytagFunc3(a, b, c)}
   let &tagfunc = string(Lambda)
   new | only
   let g:MytagFunc3_args = []
   call assert_fails("tag a19", "E433:")
   call assert_equal(['a19', '', {}], g:MytagFunc3_args)
-  call assert_fails('let &tagfunc = Lambda', 'E729:')
 
   " Test for using a lambda function with incorrect return value
   let Lambda = {s -> strlen(s)}
@@ -242,6 +278,13 @@ func Test_tagfunc_callback()
       g:MytagFunc2_args = [pat, flags, info]
       return null
     enddef
+    &tagfunc = (a, b, c) => MytagFunc2(a, b, c)
+    new | only
+    g:MytagFunc2_args = []
+    assert_fails('tag a20', 'E433:')
+    assert_equal(['a20', '', {}], g:MytagFunc2_args)
+
+    # Test for using a string(lambda)
     &tagfunc = '(a, b, c) => MytagFunc2(a, b, c)'
     new | only
     g:MytagFunc2_args = []
@@ -250,6 +293,13 @@ func Test_tagfunc_callback()
 
     # Test for using a variable with a lambda expression
     var Fn: func = (a, b, c) => MytagFunc2(a, b, c)
+    &tagfunc = Fn
+    new | only
+    g:MytagFunc2_args = []
+    assert_fails('tag a30', 'E433:')
+    assert_equal(['a30', '', {}], g:MytagFunc2_args)
+
+    # Test for using a variable with a lambda expression
     &tagfunc = string(Fn)
     new | only
     g:MytagFunc2_args = []