Please note that these changes were done automatically, using `gulp lint --fix`.
Given that the major version number was increased, there's a fair number of (primarily whitespace) changes; please see https://prettier.io/blog/2020/03/21/2.0.0.html
In order to reduce the size of these changes somewhat, this patch maintains the old "arrowParens" style for now (once mozilla-central updates Prettier we can simply choose the same formatting, assuming it will differ here).
Note that Prettier, purposely, has only limited [configuration options](https://prettier.io/docs/en/options.html). The configuration file is based on [the one in `mozilla central`](https://searchfox.org/mozilla-central/source/.prettierrc) with just a few additions (to avoid future breakage if the defaults ever changes).
Prettier is being used for a couple of reasons:
- To be consistent with `mozilla-central`, where Prettier is already in use across the tree.
- To ensure a *consistent* coding style everywhere, which is automatically enforced during linting (since Prettier is used as an ESLint plugin). This thus ends "all" formatting disussions once and for all, removing the need for review comments on most stylistic matters.
Many ESLint options are now redundant, and I've tried my best to remove all the now unnecessary options (but I may have missed some).
Note also that since Prettier considers the `printWidth` option as a guide, rather than a hard rule, this patch resorts to a small hack in the ESLint config to ensure that *comments* won't become too long.
*Please note:* This patch is generated automatically, by appending the `--fix` argument to the ESLint call used in the `gulp lint` task. It will thus require some additional clean-up, which will be done in a *separate* commit.
(On a more personal note, I'll readily admit that some of the changes Prettier makes are *extremely* ugly. However, in the name of consistency we'll probably have to live with that.)
With the removal of the (standalone) Firefox building code in PR 9566 (a year and a half ago), these files are now completely unused in the GitHub repository[1].
Hence it doesn't really seem necessary to keep fetching them with `gulp importl10n`, and the existing files in the `l10n` folder can also be removed (thanks to version control, they're easy enough to restore should the need ever arise).
The patch also allows an additional simplification, for the `gulp locale` and `gulp mozcentral` commands, since it's now possible to stop writing `l10n` files to the `extensions/firefox/` folder and instead just copy them similar to other build targets.
---
[1] They're obviously still used in `mozilla-central`, for fallback messages displayed through `PdfStreamConverter.jsm`, but that doesn't make it necessary to keep them *here* as far as I'm concerned.
Rather than having the script remove locales automatically, which seems like a heavy-handed approach at least initially, listing these for manual checking seems nice though.
Rather than having to manually maintain a static list of language codes, it's much easier to simply fetch the active ones from `mozilla-central` instead.
As part of this the code in `external/importL10n/locales.js` was modernized slightly, by using Promises/async functions to get rid of a bunch of annoying callbacks (which shouldn't be a problem for reasonably modern Node.js versions).
It gives warnings when running `gulp locale`, in a previous patch it was
explicitly asked to remove it and there is quite a bit of discussion
about the validity of the locale at
https://bugzilla.mozilla.org/show_bug.cgi?id=418485. In short, let's
remove it to prevent these issues.
This required changing the import script in two ways:
- we should use the `default` branch and not the `tip` tag since the
latter may refer to another branch than `default` (this is the case for
the `vi` locale, which caused in the files to be overwritten with
incorrect contents since `tip` referred to the
`THUNDERBIRD600b1_2018031614_RELBRANCH` branch);
- we should check if the response code is indeed 200 because recently a
script removed all empty localization files upstream (refer to
https://bugzilla.mozilla.org/show_bug.cgi?id=1443175).
Also updates a `console.log` statement in the `gulp importl10n` command (since I forgot it in a previous patch, and it didn't seem necessary with a separate patch for it).
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/
Currently `importl10n` fails, since mxr.mozilla.org has been down for a while. Based on discussions in #developers, it isn't clear to me if/when it'll be available again.
Furthermore, I'm not sure why we're even getting the l10n files through a code search tool, rather than just using the official Mozilla repository directly.
This is regression from PR 7063, causing `gulp importl10n` to fail:
```
$ gulp importl10n
[19:45:02] Using gulpfile c:\Users\Jonas\Git\pdfjs\gulpfile.js
[19:45:02] Starting 'importl10n'...
Downloading ach...
[19:45:02] 'importl10n' errored after 4.42 ms
[19:45:02] Error: EEXIST, file already exists 'c:\Users\Jonas\Git\pdfjs\l10n\ach
'
at Error (native)
at Object.fs.mkdirSync (fs.js:747:18)
at downloadLanguageFiles (c:\Users\Jonas\Git\pdfjs\external\importL10n\local
es.js:59:8)
at next (c:\Users\Jonas\Git\pdfjs\external\importL10n\locales.js:90:5)
at Object.downloadL10n (c:\Users\Jonas\Git\pdfjs\external\importL10n\locales
.js:91:5)
at Gulp.<anonymous> (c:\Users\Jonas\Git\pdfjs\gulpfile.js:92:11)
at module.exports (c:\Users\Jonas\Git\pdfjs\node_modules\gulp\node_modules\o
rchestrator\lib\runTask.js:34:7)
at Gulp.Orchestrator._runTask (c:\Users\Jonas\Git\pdfjs\node_modules\gulp\no
de_modules\orchestrator\index.js:273:3)
at Gulp.Orchestrator._runStep (c:\Users\Jonas\Git\pdfjs\node_modules\gulp\no
de_modules\orchestrator\index.js:214:10)
at Gulp.Orchestrator.start (c:\Users\Jonas\Git\pdfjs\node_modules\gulp\node_
modules\orchestrator\index.js:134:8)
```
