Jasmine recommends to use the `configure` method on the environment
during boot. This commit makes the code correspond to how it's done in
Jasmine's default boot file. The options dropdown in the HTML reporter
now works again after these changes, because this broke in the upgrade
to Jasmine 3, and the unit tests are executed in a random order by
default, which is important to make sure the unit tests are
self-contained and don't depend on the result of another unit test.
Jasmine had a major version bump and required a few minor changes in our
booting code. Most notably, using `pending` in a `describe` block is no
longer supported, so we can only return early there. On the positive
side, the unit tests now run in a random order by default, which
eliminates any dependencies between unit tests.
Note that upgrading to Webpack 4 is out of scope for this patch since
the bots cannot work well with the newly generated bundles (both
browsers on both bots do not react within 120 seconds). Webpack 4 is not
faster for us than Webpack 3, so for now there is no need to upgrade.
Please see http://eslint.org/docs/rules/object-shorthand.
Unfortunately, based on commit 9276d1dcd9, it seems that we still need to maintain compatibility with old Node.js versions, hence certain files/directories that are executed in Node.js are currently exempt from this rule.
Furthermore, since the files specific to the Chromium extension are not run through Babel, the `/extensions/chromium/` directory is also exempt from this rule.
Currently the built-in CMap files are loaded in `src/core/cmap.js` using `XMLHttpRequest` directly. For some environments that might be a problem, hence this patch refactors that to instead use a factory to load built-in CMaps on the main thread and message the data to the worker thread.
This is inspired by other recent work, e.g. the addition of the `CanvasFactory`, and to a large extent on the IRC discussion starting at http://logs.glob.uno/?c=mozilla%23pdfjs&s=12+Oct+2016&e=12+Oct+2016#c53010.
The `Driver._cleanup` method is removing all stylesheets between test runs, which causes "TypeError: styleElement.parentNode is null" console errors in `FontLoader.clear`.
As can also be seen during various tests, some of the changes I made in PR 7972 unfortunately causes console errors.
It seems that I didn't test this properly, since it *should* have been obvious to me that while tests are triggered using Node.js, the files in question are run within the *browser*.
My apologies for not testing this thoroughly, and for causing unnecessary churn in the code!
See http://eslint.org/docs/rules/brace-style.
Having the opening/closing braces on the same line can often make the code slightly more difficult to read, in particular for `if`/`else if` statements, compared to using new lines.
This patch also, for consistency with `mozilla-central`, enables the [`no-iterator`](http://eslint.org/docs/rules/no-iterator) rule. Note that this rule didn't require a single code change.
Please see http://eslint.org/docs/rules/no-unused-vars; note that this patch purposely uses the same rule options as in `mozilla-central`, such that it fixes part of issue 7957.
It wasn't, in my opinion, entirely straightforward to enable this rule compared to the already existing rules. In many cases a `var descriptiveName = ...` format was used (more or less) to document the code, and I choose to place the old variable name in a trailing comment to not lose that information.
I welcome feedback on these changes, since it wasn't always entirely easy to know what changes made the most sense in every situation.
*Please note that most of the necessary code adjustments were made in PR 7890.*
ESLint has a number of advantageous properties, compared to JSHint. Among those are:
- The ability to find subtle bugs, thanks to more rules (e.g. PR 7881).
- Much more customizable in general, and many rules allow fine-tuned behaviour rather than the just the on/off rules in JSHint.
- Many more rules that can help developers avoid bugs, and a lot of rules that can be used to enforce a consistent coding style. The latter should be particularily useful for new contributors (and reduce the amount of stylistic review comments necessary).
- The ability to easily specify exactly what rules to use/not to use, as opposed to JSHint which has a default set. *Note:* in future JSHint version some of the rules we depend on will be removed, according to warnings in http://jshint.com/docs/options/, so we wouldn't be able to update without losing lint coverage.
- More easily disable one, or more, rules temporarily. In JSHint this requires using a numeric code, which isn't very user friendly, whereas in ESLint the rule name is simply used instead.
By default there's no rules enabled in ESLint, but there are some default rule sets available. However, to prevent linting failures if we update ESLint in the future, it seemed easier to just explicitly specify what rules we want.
Obviously this makes the ESLint config file somewhat bigger than the old JSHint config file, but given how rarely that one has been updated over the years I don't think that matters too much.
I've tried, to the best of my ability, to ensure that we enable the same rules for ESLint that we had for JSHint. Furthermore, I've also enabled a number of rules that seemed to make sense, both to catch possible errors *and* various style guide violations.
Despite the ESLint README claiming that it's slower that JSHint, https://github.com/eslint/eslint#how-does-eslint-performance-compare-to-jshint, locally this patch actually reduces the runtime for `gulp` lint (by approximately 20-25%).
A couple of stylistic rules that would have been nice to enable, but where our code currently differs to much to make it feasible:
- `comma-dangle`, controls trailing commas in Objects and Arrays (among others).
- `object-curly-spacing`, controls spacing inside of Objects.
- `spaced-comment`, used to enforce spaces after `//` and `/*. (This is made difficult by the fact that there's still some usage of the old preprocessor left.)
Rules that I indend to look into possibly enabling in follow-ups, if it seems to make sense: `no-else-return`, `no-lonely-if`, `brace-style` with the `allowSingleLine` parameter removed.
Useful links:
- http://eslint.org/docs/user-guide/configuring
- http://eslint.org/docs/rules/
"text/javascript" is not a correct MIME type (the correct one is
"application/javascript") but it's not even needed; all browsers default
to the correct type and treat it as executable JS when type is ommited.
Since not all browsers recognize the "application/javascript" MIME type
the only way to both stay compliant and to support all popular browsers
is to omit the type. It's also shorter this way.
