SystemJS version 0.21.0 works, but version 0.21.1 breaks with various
`Unable to load transpiler to transpile` errors. Pin the version to
0.21.0 for now to avoid this issue.
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.
Since multiple empty lines is virtually unused in the code-base, and the few cases that do exist look like "typos", let's enforce greater consistency here; please see https://eslint.org/docs/rules/no-multiple-empty-lines.
The `gulp-util` module is now deprecated and authors are asked to stop
using it (refer to https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5 for
more information).
PDF.js does not rely on it that much, fortunately, so it's relatively
easy for us to remove the dependency. This patch does that by making the
following changes:
- Require `gulp-zip` version 4.1.0 or higher since they already removed
their `gulp-util` dependency in that version.
- Replace `gulp-util.log` with the `fancylog` module as recommended in
the article above.
- Replace `gulp-util.File` with the `Vinyl` module as recommended in the
article above.
The only change I had to make for Vinyl is removing the `base` and `cwd`
lines since they may not be empty strings anymore. This way we fall back
to the defaults Vinyl provides, which for us doesn't matter since we
move the file afterwards anyway. Moreover, I used `vfs` for `vinyl-fs`
in the `Gulpfile` to avoid confusion with `vinyl` (which is also how the
documentation names the variable).
This is all we can do on our side; the other modules that still use
`gulp-util` must be updated upstream.
To support this, the following changes have to be made as well:
- Ignore `package-lock.json` since NPM creates it, but we should not
have it in the repository.
- Switch from `babel-preset-es2015` to `babel-preset-env` to resolve
the deprecation warning in the test logs. The latter is more recent
and flexible, but should be the same functionality-wise.
- `transform` now needs to have the `utf-8` encoding option provided.
If not given, it will call the callback with a `Buffer` object,
which results in an unhandled promise rejection since what is
returned from the callback is a string, not a `Buffer`.
By updating to uglify-es, rather than uglify-js, the minifier *itself* now supports ES6 code. This means that it's now possible to minify code built with `PDFJS_NEXT = true` set, i.e. with Babel transpilation disabled, which wasn't the case previously.
Note that uglify-es is based on the API of uglify-js v3, which differs from the one that we previously used.
Of particular importance is the fact that it's no longer possible to provide a path to a file for minification, but one must instead directly provide the source of the file.
For more information, please see https://github.com/mishoo/UglifyJS2/tree/harmony
See https://eslint.org/docs/rules/for-direction; helps avoid typos that would cause infinite `for` loops.
Also, updates `eslint` and `eslint-plugin-mozilla` to the latest available versions.
I've gotten tired of having to manually re-install the `ttest` package on numerous occasions when benchmarking changes, so let's just list it in package.json to simplify things.
*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/
This requires the `run-sequence` dependency because Gulp does not have a
way to run sequences of tasks inside a Gulp task. Gulp 4.0 will have
support for this, but until that is released this is the recommended way
to implement it.
