vim-patch:8.1.2341: not so easy to interrupt a script programatically

Problem:    Not so easy to interrupt a script programatically.
Solution:   Add the interrupt() function. (Yasuhiro Matsumoto, closes vim/vim#2834)
https://github.com/vim/vim/commit/67a2deb9cb4ac2224cb1e4d240a5d0659f036264

4 files changed, 46 insertions, 11 deletions

diff --git a/src/nvim/eval.lua b/src/nvim/eval.lua
index 023c60f118..a5544435d2 100644
--- a/src/nvim/eval.lua
+++ b/src/nvim/eval.lua
@@ -191,6 +191,7 @@ return {
     inputsave={},
     inputsecret={args={1, 2}},
     insert={args={2, 3}},
+    interrupt={args=0},
     invert={args=1},
     isdirectory={args=1},
     isinf={args=1},
diff --git a/src/nvim/eval/funcs.c b/src/nvim/eval/funcs.c
index 1a80d4d4bd..a81f789f0f 100644
--- a/src/nvim/eval/funcs.c
+++ b/src/nvim/eval/funcs.c
@@ -4717,6 +4717,14 @@ static void f_insert(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   }
 }
 
+// "interrupt()" function
+static void f_interrupt(typval_T *argvars FUNC_ATTR_UNUSED,
+                        typval_T *rettv FUNC_ATTR_UNUSED,
+                        FunPtr fptr FUNC_ATTR_UNUSED)
+{
+  got_int = true;
+}
+
 /*
  * "invert(expr)" function
  */
diff --git a/src/nvim/ex_eval.c b/src/nvim/ex_eval.c
index 81274fcf2a..e99e5b01cd 100644
--- a/src/nvim/ex_eval.c
+++ b/src/nvim/ex_eval.c
@@ -87,17 +87,16 @@
  */
 static int cause_abort = FALSE;
 
-/*
- * Return TRUE when immediately aborting on error, or when an interrupt
- * occurred or an exception was thrown but not caught.  Use for ":{range}call"
- * to check whether an aborted function that does not handle a range itself
- * should be called again for the next line in the range.  Also used for
- * cancelling expression evaluation after a function call caused an immediate
- * abort.  Note that the first emsg() call temporarily resets "force_abort"
- * until the throw point for error messages has been reached.  That is, during
- * cancellation of an expression evaluation after an aborting function call or
- * due to a parsing error, aborting() always returns the same value.
- */
+// Return true when immediately aborting on error, or when an interrupt
+// occurred or an exception was thrown but not caught.  Use for ":{range}call"
+// to check whether an aborted function that does not handle a range itself
+// should be called again for the next line in the range.  Also used for
+// cancelling expression evaluation after a function call caused an immediate
+// abort.  Note that the first emsg() call temporarily resets "force_abort"
+// until the throw point for error messages has been reached.  That is, during
+// cancellation of an expression evaluation after an aborting function call or
+// due to a parsing error, aborting() always returns the same value.
+// "got_int" is also set by calling interrupt().
 int aborting(void)
 {
   return (did_emsg && force_abort) || got_int || current_exception;
diff --git a/src/nvim/testdir/test_interrupt.vim b/src/nvim/testdir/test_interrupt.vim
new file mode 100644
index 0000000000..111752d16a
--- /dev/null
+++ b/src/nvim/testdir/test_interrupt.vim
@@ -0,0 +1,27 @@
+" Test behavior of interrupt()
+
+let s:bufwritepre_called = 0
+let s:bufwritepost_called = 0
+
+func s:bufwritepre()
+  let s:bufwritepre_called = 1
+  call interrupt()
+endfunction
+
+func s:bufwritepost()
+  let s:bufwritepost_called = 1
+endfunction
+
+func Test_interrupt()
+  new Xfile
+  let n = 0
+  try
+    au BufWritePre Xfile call s:bufwritepre()
+    au BufWritePost Xfile call s:bufwritepost()
+    w!
+  catch /^Vim:Interrupt$/
+  endtry
+  call assert_equal(1, s:bufwritepre_called)
+  call assert_equal(0, s:bufwritepost_called)
+  call assert_equal(0, filereadable('Xfile'))
+endfunc