Assert that sourcemaps are actually valid + empty map issue

[johnnyshields]

One of the tests (below) is failing as it is not valid to have an empty sourcemap:

  it('can ignore empty content', function() {
    var node = concat(firstFixture, {
      outputFile: '/nothing.js',
      inputFiles: ['nothing/*.js'],
      allowNone: true
    });
    builder = new broccoli.Builder(node);
    return builder.build().then(function(result) {
      expectValidSourcemap('nothing.js').in(result);
    });
  });

{"version":3,"sources":[],"sourcesContent":[],"names":[],"mappings":"","file":"nothing.js"}

  1) sourcemap-concat can ignore empty content:
     AssertionError: There were no sources in the file

[johnnyshields]

@ef4 you might want to take a look at this. There is one existing test case which is not generating a valid sourcemap (i.e. fails validation using a the sourcemap-validator lib on NPM)

[Turbo87]

@johnnyshields sorry for causing the conflicts on your branch, can you rebase on master?

[Turbo87]

maybe we should keep using expectFile() here and add a code comment about why expectValidSourcemap() is not used

[johnnyshields]

If we are generating a .map file, it should always pass validation. Otherwise, downstream parsers may choke on the map--many of them are quite brittle.

An alternative would be to not generate a .map file.

The current behavior--generating an invalid .map--is not acceptable IMHO.

[Turbo87]

@stefanpenner any opinions on this?

[ef4]

I agree that we should not generate an invalid map file. We could generate a valid one that has nothing in it.

[Turbo87]

We could generate a valid one that has nothing in it.

if I understand the situation correctly that is what we are currently doing. we are generating a map for nothing/*.js but the whole nothing folder doesn't exist, which results in sources of the map being empty, which according to the validator is invalid.

[Turbo87]

I just ran our empty source maps against sourcemaps.io and they are not complaining about the empty sources list.

see https://sourcemaps.io/validate?url=https%3A%2F%2Fgist.githubusercontent.com%2FTurbo87%2Fe39b740c872227698227d3fc7005ad36%2Fraw%2Fdc5f1ca29a8bb98030f63773cc2c4561026711ea%2Fnothing.js

[stefanpenner]

Although not perfect, it would seem that:

1. an empty map file is valid, if someone asks for a map they get a map even if it is empty, as long as it is well formed.
2. the validate tool seems to not handle this case correctly.
3. unless new information surfaces, we should: skip the validator for this one scenario, and continue the existing behavior

[stefanpenner]

ben-ng/sourcemap-validator#4

[johnnyshields]

@Turbo87 I've done the rebase. Please take over this PR and fix as necessary.

[Turbo87]

awesome, thanks!