YANG _emit_stmt() logic is wrong for multi-line arguments

[wlupton]

I believe that the YANG _emit_stmt() logic is wrong for multi-line arguments. The YANG shown below has two presence statements, both of which are 66 characters long but the first has a multi-line argument.

With this command (using the latest pyang from GitHub master):

% pyang presence-bug.yang --format yang --yang-line-length=66

the first one is (wrongly) wrapped to the next line, but the second one (correctly) isn't:

      presence
        "Presence of an aardvark strongly suggests that the
         'a' key is working correctly.";

      presence "Presence of a bison suggests that we should run.";

There appears to be an "off by three" error, because it's necessary to set --yang-line-length=69 to prevent the first one from wrapping:

      presence "Presence of an aardvark strongly suggests that the
                'a' key is working correctly.";

I think that I see what the problem is (actually I think there are two separate problems) and will create a PR.

YANG

module presence-bug {
  namespace "urn:presence-bug";
  prefix presence-bug;
  container root {
    container aardvark {
      description "The length of the next line is 66.";
      presence "Presence of an aardvark strongly suggests that the
                'a' key is working correctly.";
    }
    container bison {
      description "The length of the next line is 66.";
      presence "Presence of a bison suggests that we should run.";
    }
  }
}

[fredgan]

Wow, you are really careful!

[wlupton]

@fredgan, someone complained! We pass all BBF YANG through the edit transform to add metadata and reformat it, and people noticed that some of the presence statements were unnecessarily wrapped.

[wlupton]

Hmm. There doesn't seem to be a reference to PR #776. Now there is.