API: nvim_source_output

- Similar to nvim_source but will capture the output
- Add meaningful VimL tracebacks for nvim_source
- Handle got_int
- Add error reporting

3 files changed, 111 insertions, 12 deletions

diff --git a/src/nvim/api/vim.c b/src/nvim/api/vim.c
index 10ece6bc22..bf722b4f4e 100644
--- a/src/nvim/api/vim.c
+++ b/src/nvim/api/vim.c
@@ -73,14 +73,63 @@ void api_vim_free_all_mem(void)
   map_free(String, handle_T)(namespace_ids);
 }
 
-void nvim_source(String command, Error *err)
-  FUNC_API_SINCE(7)
+/// Executes a multiline block of ex-commands from a string.
+///
+/// On execution error: fails with VimL error, does not update v:errmsg.
+///
+/// @param src      String containing the ex-commands
+/// @param[out] err Error details (Vim error), if any
+void nvim_source(String src, Error *err) FUNC_API_SINCE(7)
 {
   try_start();
-  do_source_str(command.data);
+  do_source_str(src.data, "nvim_source(..)");
   try_end(err);
 }
 
+/// Executes a multiline block of ex-commands from a string and returns its
+/// (non-error) output. Shell |:!| output is not captured.
+///
+/// On execution error: fails with VimL error, does not update v:errmsg.
+///
+/// @param src      String containing the ex-commands
+/// @param[out] err Error details (Vim error), if any
+String nvim_source_output(String src, Error *err) FUNC_API_SINCE(7)
+{
+  const int save_msg_silent = msg_silent;
+  garray_T *const save_capture_ga = capture_ga;
+  garray_T capture_local;
+  ga_init(&capture_local, 1, 80);
+
+  try_start();
+  msg_silent++;
+  capture_ga = &capture_local;
+  do_source_str(src.data, "nvim_source_output(..)");
+  capture_ga = save_capture_ga;
+  msg_silent = save_msg_silent;
+  try_end(err);
+
+  if (ERROR_SET(err)) {
+    goto theend;
+  }
+
+  if (capture_local.ga_len > 1) {
+    String s = (String){
+        .data = capture_local.ga_data,
+        .size = (size_t)capture_local.ga_len,
+    };
+    // redir usually (except :echon) prepends a newline.
+    if (s.data[0] == '\n') {
+      memmove(s.data, s.data + 1, s.size - 1);
+      s.data[s.size - 1] = '\0';
+      s.size = s.size - 1;
+    }
+    return s;  // Caller will free the memory.
+  }
+theend:
+  ga_clear(&capture_local);
+  return (String)STRING_INIT;
+}
+
 /// Executes an ex-command.
 ///
 /// On execution error: fails with VimL error, does not update v:errmsg.
diff --git a/src/nvim/ex_cmds2.c b/src/nvim/ex_cmds2.c
index eec689a28d..bda7b4e8b5 100644
--- a/src/nvim/ex_cmds2.c
+++ b/src/nvim/ex_cmds2.c
@@ -3025,7 +3025,7 @@ typedef struct {
 ///
 /// @return pointer to allocated line, or NULL for end-of-file or
 ///         some error.
-static char_u *get_str_line(int c, void *cookie, int ident)
+static char_u *get_str_line(int c, void *cookie, int indent, bool do_concat)
 {
   GetStrLineCookie *p = cookie;
   size_t i = p->offset;
@@ -3037,19 +3037,31 @@ static char_u *get_str_line(int c, void *cookie, int ident)
   }
   char buf[2046];
   char *dst;
-  dst = xstpncpy(buf, (char *)p->buf+p->offset, i - p->offset);
+  dst = xstpncpy(buf, (char *)p->buf + p->offset, i - p->offset);
   if ((uint32_t)(dst - buf) != i - p->offset) {
     smsg(_(":source error parsing command %s"), p->buf);
     return NULL;
   }
-  buf[i-p->offset]='\0';
+  buf[i - p->offset] = '\0';
   p->offset = i + 1;
   return (char_u *)xstrdup(buf);
 }
 
-int do_source_str(const char *cmd)
+int do_source_str(const char *cmd, const char *traceback_name)
 {
-  int retval;
+  char_u *save_sourcing_name = sourcing_name;
+  linenr_T save_sourcing_lnum = sourcing_lnum;
+  char_u sourcing_name_buf[256];
+  if (save_sourcing_name == NULL) {
+    sourcing_name = (char_u *)traceback_name;
+  } else {
+    snprintf((char *)sourcing_name_buf, sizeof sourcing_name_buf,
+             "%s called at %s:%"PRIdLINENR, traceback_name, save_sourcing_name,
+             save_sourcing_lnum);
+    sourcing_name = sourcing_name_buf;
+  }
+  sourcing_lnum = 0;
+
   GetStrLineCookie cookie = {
     .buf = (char_u *)cmd,
     .offset = 0,
@@ -3057,10 +3069,18 @@ int do_source_str(const char *cmd)
   const sctx_T save_current_sctx = current_sctx;
   current_sctx.sc_sid = SID_STR;
   current_sctx.sc_seq = 0;
-  current_sctx.sc_lnum = 0;
-  retval = do_cmdline(NULL, get_str_line, (void *)&cookie,
-                      DOCMD_VERBOSE|DOCMD_NOWAIT|DOCMD_REPEAT);
+  current_sctx.sc_lnum = save_sourcing_lnum;
+  int retval = FAIL;
+  do_cmdline(NULL, get_str_line, (void *)&cookie,
+             DOCMD_VERBOSE | DOCMD_NOWAIT | DOCMD_REPEAT);
+  retval = OK;
+  if (got_int) {
+    EMSG(_(e_interr));
+  }
+
   current_sctx = save_current_sctx;
+  sourcing_lnum = save_sourcing_lnum;
+  sourcing_name = save_sourcing_name;
   return retval;
 }
 
diff --git a/test/functional/api/vim_spec.lua b/test/functional/api/vim_spec.lua
index a01ef2d6dd..9a7744142a 100644
--- a/test/functional/api/vim_spec.lua
+++ b/test/functional/api/vim_spec.lua
@@ -84,7 +84,7 @@ describe('API', function()
     it(':verbose set {option}?', function()
       nvim('source', 'set nowrap')
       eq('nowrap\n\tLast set from :source (no file)',
-        nvim('command_output', 'verbose set wrap?'))
+        nvim('source_output', 'verbose set wrap?'))
     end)
 
     it('multiline input', function()
@@ -165,6 +165,36 @@ describe('API', function()
       eq('overwritten', request('nvim_get_var', 'x5'))
       os.remove(fname)
     end)
+
+    it('traceback', function()
+      local fname = helpers.tmpname()
+      write_file(fname, 'echo "hello"\n')
+      local sourcing_fname = helpers.tmpname()
+      write_file(sourcing_fname, 'call nvim_source("source '..fname..'")\n')
+      meths.source('set verbose=2')
+      print()
+      local traceback_output = 'line 0: sourcing "'..sourcing_fname..'"\n'..
+        'line 0: sourcing "'..fname..'"\n'..
+        'hello\n'..
+        'finished sourcing '..fname..'\n'..
+        'continuing in nvim_source(..) called at '..sourcing_fname..':1\n'..
+        'finished sourcing '..sourcing_fname..'\n'..
+        'continuing in nvim_source(..) called at nvim_source_output(..):0'
+      eq(traceback_output, meths.source_output('call nvim_source("source '..sourcing_fname..'")'))
+      os.remove(fname)
+      os.remove(sourcing_fname)
+    end)
+  end)
+
+  describe('nvim_source_output', function()
+    it('multiline input', function()
+      eq('this is spinal tap',
+         nvim('source_output', 'lua <<EOF\n\n\nprint("this is spinal tap")\n\n\nEOF'))
+    end)
+
+    it('empty output', function()
+      eq('', nvim('source_output', 'echo'))
+    end)
   end)
 
   describe('nvim_command', function()