Issue 6437 - Filter out patterns that do not match DOM mutations

This builds on https://codereview.adblockplus.org/29712655/

There are three types of mutations: "attributes", "characterData", and "childList"

If only an attribute has changed, we don't have to process -abp-contains, for example. Similarly if only character data has changed, it should not affect -abp-has (unless it contains a nested -abp-contains) or -abp-properties. We can avoid doing a lot of processing by filtering out the patterns that do not match the given DOM mutations.

[Manish Jethani, 2018-03-02 13:20:17]

Patch Set 1

See description. This builds on https://codereview.adblockplus.org/29712655/

There are some obvious optimizations here but that'll be a separate patch.

[Manish Jethani, 2018-03-02 13:23:42]

https://codereview.adblockplus.org/29713565/diff/29713566/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29713565/diff/29713566/lib/content/elemHid...
lib/content/elemHideEmulation.js:410: return pattern.selectors.some(
One obvious optimization is that a pattern can remember whether or not it
matches a certain kind of mutation, since patterns are immutable once created
(we can formalize this with a class). Next patch.

https://codereview.adblockplus.org/29713565/diff/29713566/lib/content/elemHid...
lib/content/elemHideEmulation.js:452: if (!stylesheets && !mutations)
Do full processing.

[Manish Jethani, 2018-03-02 13:26:27]

Patch Set 2: Fix formatting

[Manish Jethani, 2018-03-20 09:41:33]

Patch Set 3: Rebase

You could test this out on my home page https://manishjethani.com/ by adding the
following two filters:

  manishjethani.com#?#p:-abp-contains(blank)
  manishjethani.com#?#div:-abp-has([title="Follow me on Twitter"])

Load the page (elements will be hidden), then open the JS console and enter the
following:

  document.getElementsByClassName("caption")[0].innerText = "Hello"

This mutation of "characterData" type does not affect the second pattern, so the
second pattern gets filtered out.

Also try this in the console:

  document.getElementsByClassName("caption")[0].setAttribute("data-foo", "")

Similarly, this mutation of "attributes" type does not affect the first pattern,
so the first pattern gets filtered out.

https://codereview.adblockplus.org/29713565/diff/29728575/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29713565/diff/29728575/lib/content/elemHid...
lib/content/elemHideEmulation.js:462: () => new Map([
This is a cached property also so the map gets created only once.

[hub, 2018-04-17 21:43:47]

Do you think it is possible to write a test? (see
`test/browser/elemHideEmulation.js`)

[Manish Jethani, 2018-04-24 12:43:02]

Patch Set 4: Rebase
Patch Set 5: Add tests

I've added tests now.

Unfortunately it's hard to test if only the desired patterns are being
processed, but let me see if I can do that. These tests are only checking that
it hides the right elements successfully.

https://codereview.adblockplus.org/29713565/diff/29760611/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29713565/diff/29760611/lib/content/elemHid...
lib/content/elemHideEmulation.js:230: preferHideWithSelector: true,
This is a bug. If there's only the filter "example.com#?#div" it always tries to
set the style property rather than inserting the selector. I'll file a separate
issue for this.

https://codereview.adblockplus.org/29713565/diff/29760611/test/browser/elemHi...
File test/browser/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29713565/diff/29760611/test/browser/elemHi...
test/browser/elemHideEmulation.js:145: selector => ({selector, text: selector})
This is useful for debugging.

[Manish Jethani, 2018-04-24 13:58:32]

Patch Set 6: Process plain selectors on DOM mutations

https://codereview.adblockplus.org/29713565/diff/29760642/lib/content/elemHid...
File lib/content/elemHideEmulation.js (right):

https://codereview.adblockplus.org/29713565/diff/29760642/lib/content/elemHid...
lib/content/elemHideEmulation.js:227: this.dependsOnDOM =
this.maybeDependsOnAttributes;
OK, since Trac #6618 is rejected we have to process these selectors when there's
a DOM mutation (otherwise the testPlainAttributeOnDomMutation test doesn't
pass).

[hub, 2018-04-30 13:29:37]

LGTM