Fixes gh-3139
Closes gh-3140

One test in the attribute module was overwriting jQuery.expr.attrHandle.checked
and wasn't restoring the original state after it finished. It started causing
issues for another checked-related test.

Attributes are no longer always treated as lowercase, although hooks for
them are. This commit fixes a no longer correct comment.

Attribute hooks are determined for the lowercase versions of attribute names
but this has not been reflected in the bool attribute hooks. The code that
temporarily removed a handler to avoid an infinite loop was removing an
incorrect handler causing stack overflow.

Fixes gh-3133
Refs gh-2914
Refs gh-2916
Closes gh-3134

Progress parameters are now correctly propagated from a deferred to which
another deferred resolved unwrapping it.

Thanks to @gibson042 for the report and a clear description of the problem
and the needed fix.

Fixes gh-3062
Closes gh-3150

Ref gh-3104
Close gh-3152

Use eslint pragmas, fix new errors, etc

Closes gh-3148

* Bump eslint-config-jquery package to 0.1.4 version

* Add subtask "dist" to "eslint" task and add it to the build task list

* Make gitignore globs more flexible for the "dist" folder

Fixes gh-3169

Also, expose jQuery.readyException that allows to overwrite the default
ready error handler.

Fixes gh-3174
Closes gh-3210

Since it is not supported by older node versions :/

The new regex from after the switch from JSHint to ESLint wasn't catching
the ESLint pragma correctly.

Also, the spacing of the pragma comment was updated to match other comments.

ESLint 3.0 drops support for Node.js older than 4.x. To be able to update
to this version and yet not block our contributors from building jQuery
on older Node.js (at least until it's supported by upstream) this commit
makes ESLint skipped on older Node; a proper message is displayed then.

Fixes gh-3222

ESLint is now skipped in Node older than 4.x so we're safe.

Refs gh-3222

Closes gh-3176

Currently the "all" target for the eslint task includes way more than
the "dev" & "dist" targets combined and those 2 tasks are the one run in
`npm test`.

Fixes gh-3246

`.eslintrc` format is deprecated -
http://eslint.org/docs/user-guide/configuring#configuration-file-formats

Fixes gh-3248
Closes gh-3247

Closes gh-3255

Fixes gh-3224

Fixes gh-3229
Closes gh-3253

…cessary

Current width/height cssHook reads the computed position style even if not
necessary as the browser passes the scrollboxSize support test. That has been
changed.

This commit also makes the scrollboxSize support test in line with all others
(i.e. only return true or false) and changes the variable name in the hook
to make the code clearer.

Fixes gh-4185
Closes gh-4187

Allow `isAttached` to check Shadow DOM for attachment.

Fixes gh-3504
Closes gh-3996
Ref gh-3977

- getResponseHeader(key) combines all header values for the provided key into a
single result where values are concatenated by ', '. This does not happen for
IE11 since multiple values for the same header are returned on separate lines.
This makes the function only return the last value of the header for IE11.
- Updated ajax headers test to better cover Object.prototype collisions

Close gh-4173
Fixes gh-3403

- Use getClientRects() to explicitly detect hidden/disconnected
  elements

Close gh-4223
Fixes gh-4102

Close gh-4248

Read target[name] only when it's needed.

In addition to doing the property read-only when needed, this
avoids a slow path in V8 (see the issue for more details).

Fixes gh-4245
Closes gh-4246

Fixes gh-4126
Closes gh-4243

IE and iOS <10 XHR transport does not succeed on data: URIs
Ref gh-4243
Ref gh-4126
Closes gh-4258

Android Browser only returns the last value for each header so there's no way
for jQuery get all parts.

Closes gh-4259
Ref gh-3403
Ref gh-4173

Fixes gh-3541
Closes gh-4269

Old iOS & Android Browser versions support script-src but not nonce, making the
nonce test impossible to run. Browsers not supporting CSP at all are not
a problem as they'll skip script-src restrictions completely.

Ref gh-3541
Ref gh-4269
Ref c7c2855

PR #3869 added support for `<script type="module">` & some support for
the `nomodule` attribute but with no tests for `nomodule` and with the
attribute only respected on inline scripts. This commit adds support for
source-based scripts as well. It also adds tests for `nomodule`, including
making sure legacy browsers execute such scripts as they'd natively do - that's
the whole point of `nomodule` scripts, after all.

Fixes gh-4281
Closes gh-4282
Ref gh-3871
Ref gh-3869

Fixes gh-4278
Closes gh-4280
Ref gh-3541
Ref gh-4269

JSFiddle doesn't support IE (even 11) anymore so we shouldn't advise users
to use it to create test cases. To make people have a choice, add CodePen
to the list.

Also, link to specific starter templates so that novices don't need to spend
time thinking how to set up the basic structure.

Closes gh-4289

Also, run `grunt npmcopy` to sync the "external" directory with dependencies
from package.json. For example, the Sinon library version didn't match.

Ref gh-4234
Closes gh-4297

The only packages not fully updated are:
- qunitjs & karma-qunit as that's a QUnit 2.x update that will require some
changes and we'll do that later
- jsdom as we need to first rewrite the test with the Symbol polyfill - newer
jsdom versions don't work with such a hacked Symbol instance
- sinon as the v2 -> v7 upgrade requires to update our unit tests
- uglify-js & grunt-contrib-uglify as latest uglify-js versions slightly worsen
the minified gzipped size

Closes gh-4227
Closes gh-4228
Closes gh-4230
Closes gh-4232

We had quite a few obsolete globals declared in various ESLint config files. We also no longer allow to rely on the `noGlobal` & `jQuery` globals in the built file which is not needed.

Closes gh-4301

… test

So far, we've been testing that jQuery element iteration works with polyfilled
Symbol & transpiled for-of via a Node test with jsdom with the Symbol global
removed. Unfortunately, jsdom now requires Symbol to be present for its internal
functionality so such a test is no longer possible. Instead, it's been migrated
to an iframe test with transpiled JavaScript.

This PR also enables us to use ECMAScript 2017 or newer in Node.js code.

Closes gh-4305

Node.js 10 has been in Active LTS since 2018-04-24 and Node.js 8 is now in
maintenance mode.

See https://github.com/nodejs/Release for more details.

Closes gh-4311

Closes gh-4307