Async custom importer sass.NULL behavior different than sync importer

[lingram-rmn]

Returning sass.NULL asynchronously does not result in the default libsass import behavior. It's quite possible that this will turn out to be an upstream bug in libsass, but I thought I would start here.

Repro

Run the following in a context where node-sass is npm-installed:

var assert = require('assert');
var fs = require('fs');
var path = require('path');
var sass = require('node-sass');

fs.writeFileSync(
  path.resolve('entry.scss'),
  [
    '/* entry.scss */',
    '@import "./import.scss";'
  ].join('\n')
);

fs.writeFileSync(
  path.resolve('import.scss'),
  '/* import.scss */'
);

var syncResult;
sass.render({
  file: path.resolve('entry.scss'),
  importer: function (url, prev, done) {
    return sass.NULL;
  }
}, function (err, result) {
  if (err) {
    throw err;
  }

  syncResult = result.css.toString();
});

sass.render({
  file: path.resolve('entry.scss'),
  importer: function (url, prev, done) {
    done(sass.NULL);
  }
}, function (err, result) {
  if (err) {
    throw err;
  }

  setTimeout(function () {
    assert.strictEqual(result.css.toString(), syncResult);
  }, 0);
});

Expected

Script exits without an error.

Observed

The equality assertion fails:

assert.js:86
  throw new assert.AssertionError({
        ^
AssertionError: '/* entry.scss */\n' === '/* entry.scss */\n/* import.scss */\n'
    at null._onTimeout (/Users/lingram/Projects/node-sass-importer-bug/test.js:44:12)
    at Timer.listOnTimeout (timers.js:119:15)

[JohnAlbin]

@lingram-rmn I'm not certain, but is this a duplicate of issue #1291? Or possibly a manifestation of the same problem that the importer's node-sass is not equal to the node-sass that calls the importer?

[lingram-rmn]

I don't think it's a duplicate, no. There's only one node-sass instance
involved.
On Dec 5, 2015 7:48 PM, "John Albin Wilkins" notifications@github.com
wrote:

@lingram-rmn https://github.com/lingram-rmn I'm not certain, but is
this a duplicate of issue #1291
#1291? Or possibly a
manifestation of the same problem that the importer's node-sass is not
equal to the node-sass that calls the importer?

—
Reply to this email directly or view it on GitHub
#1296 (comment).

This e-mail, including attachments, contains confidential and/or
proprietary information, and may be used only by the person or entity to
which it is addressed. The reader is hereby notified that any
dissemination, distribution or copying of this e-mail is prohibited. If you
have received this e-mail in error, please notify the sender by replying to
this message and delete this e-mail immediately.

[saper]

I am not very happy about this fix, but can you check if #1308 works? It fixes it for the script above.

[xzyfer]

@lingram-rmn we've confirmed this issue. It will be fixed in v3.4.3.

[lingram-rmn]

👏 Thanks! I'm back in the office on Monday and will test the patch out then. 👏