Prevent empty selectors from being migrated from legacy cosmetic filters

[antonok-edm]

Test plan

See brave/brave-core#8270

Description

Followup to #9581

As visible in #9581 (comment), migrating the legacy cosmetic filtering implementation to the brave://adblock "Custom filters" box results in some invalid rules that have no CSS selector.

This appears to be caused by the logic for retrieving the selector from window.prompt - a fallback to an empty string is used, even though no rule should be generated if an empty selector is passed, or if the prompt is closed rather than submitted.

This should be fixed by updating the prompt to trim whitespace from the selector, and only adding the rule if it is non-empty. Additionally, any filters migrated from the legacy implementation should be ignored if the selector is blank.

[stephendonner]

Verified PASSED using the testplan from brave/brave-core#8270 with

Brave	1.23.68 Chromium: 90.0.4430.51 (Official Build) (x86_64)
Revision	32e5fa33a31641bded70a90e60121060691e7125-refs/branch-heads/4430@{#927}
OS	macOS Version 11.2.3 (Build 20D91)

Verified the following cases:

Migration

Using a previous browser version (1.21.77):

1. Visit brave://adblock in a new tab
2. Add some text of your choice to the "Custom filters" box

I added

SupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidocious

1234567890
foo
facebook.com
https://www.cnn.com
!@#$%^&*()_+

1. Visit a website of your choice (aol.com, twitch.tv, and sfgate.com)
2. Right-click on a page element of your choice
3. Select "Brave > Block element via selector"
4. Confirm the block
5. Repeat steps 3-6 a few times to block a variety of items through the legacy system. Block multiple items on the same page at least once. Keep track of what is being blocked. Be sure to close the prompt window, press cancel, or just press OK with an empty rule each at least once.

aol.com (1.21.77)	twitch.tv (1.21.77)	sfgate.com (1.21.77)

Then, testing the same profile after the version upgrade:

1. Visit brave://adblock in a new tab
2. Verify that any text previously added to the "Custom filters" box is still present
3. Verify that new lines have been added to the "Custom filters" box, including one corresponding to each item previously blocked using the right click menu, and that no rules were generated that are empty after the ##

Verified there are no empty filter-rule sets in brave://adblock

4. Revisit some of the websites and confirm that any previously blocked items are still hidden

Verified that previously blocked elements are still blocked

aol.com (1.23.68)	twitch.tv (1.23.68)	sfgate.com (1.23.68)

Adding new filters

Just on 1.23.68:

1. Visit a website of your choice (cnn.com)
2. Right-click on a page element of your choice
3. Select "Brave > Block element via selector"
4. Confirm the block
5. Verify that the blocked item is hidden, and remains hidden after a page refresh
6. Reopen or refresh brave://adblock and verify that a new line has been added corresponding to the newly blocked item
7. Repeat steps 1-6 at least one more time
8. Repeat steps 1-6 for each of the following, and ensure that *no* new lines are created in brave://adblock: closing the prompt window, pressing cancel on the prompt window, and pressing OK with an empty rule in the prompt window

Verified there are no empty filter-rule sets in brave://adblock

cnn.com (blocking content / empty selectors)	brave://adblock filter set

Reference images (no blocked items)

aol.com	twitch.tv	sfgate.com	cnn.com

---

Verification passed on

Brave | 1.23.59 Chromium: 89.0.4389.114 (Official Build) dev (64-bit)
-- | --
Revision | 1ea76e193b4fadb723bfea2a19a66c93a1bc0ca6-refs/branch-heads/4389@{#1616}
OS | Windows 10 OS Version 2004 (Build 19041.867)

• Verified the test plan from Forbid new empty cosmetic filters from being created via right click menu brave-core#8270

Migration

Installed 1.21.56 and added random text to Custom filter box

Visit a website of your choice (aol.com, twitch.tv, and sfgate.com) and block few elements on each site

aol.com (1.21.56)	twitch.tv (1.21.56)	sfgate.com (1.21.56)

Upgrade the profile to 1.23.56 and verified the items below:

1. Visit brave://adblock in a new tab
2. Verify that any text previously added to the "Custom filters" box is still present
3. Verify that new lines have been added to the "Custom filters" box, including one corresponding to each item previously blocked using the right click menu, and that no rules were generated that are empty after the ##

Verified there are no empty filter-rule sets in brave://adblock

4. Revisit some of the websites and confirm that any previously blocked items are still hidden

Verified that previously blocked elements are still blocked

aol.com (1.23.59)	twitch.tv (1.23.59)	sfgate.com (1.23.59)

Adding new filters

Clean profile 1.23.59. Opened a CNN.COM site and blocked few elements via Brave->Block element via elector and ensured blocked elements on the sites are hidden even after the page reload/refresh

Opened brave://adblock and ensured new line has been added corresponding to the newly blocked items for cnn.com

ensured that no new lines are created in brave://adblock: closing the prompt window, pressing cancel on the prompt window, and pressing OK with an empty rule in the prompt window

---

Verified passed with

Brave	1.23.68 Chromium: 90.0.4430.51 (Official Build) (64-bit)
Revision	32e5fa33a31641bded70a90e60121060691e7125-refs/branch-heads/4430@{#927}
OS	Linux

Verified test plan from brave/brave-core#8156 (comment)

Migration (Upgrade)

Using a previous browser version (I used 1.22.71):

1. Visit brave://adblock in a new tab
2. Add some text of your choice to the "Custom filters" box

I added:

SupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidociousSupercalifragilisticexpialidocious

1234567890
foo
facebook.com
https://www.cnn.com
!@#$%^&*()_+

3. Visit a website of your choice

aol.com, twitter.com

4. Right-click on a page element of your choice
5. Select "Brave > Block element via selector"
6. Confirm the block
7. Repeat steps 3-6 a few times to block a variety of items through the legacy system. Block multiple items on the same page at least once. Keep track of what is being blocked. Be sure to close the prompt window, press cancel, or just press OK with an empty rule each at least once.
   • On both pages closed prompt window without saving (used "x")
   • On both pages selected Cancel on prompt window
   • On both pages removed the rule text and selected "OK"

Then, testing the same profile after the upgrade (1.23.68):

1. Visit brave://adblock in a new tab
2. Verify that any text previously added to the "Custom filters" box is still present
3. Verify that new lines have been added to the "Custom filters" box, including one corresponding to each item previously blocked using the right click menu, and that no rules were generated that are empty after the ##. Confirmed there are no empty filter-rule sets in brave://adblock
4. Revisit some of the websites and confirm that any previously blocked items are still hidden
   • On aol.com, blocked horoscope box on right side, AOL logo in top left, search bar at top of page, and search button at top of page
   • On twitter.com blocked the logo in middle of page

brave://adblock comparison before and after upgrade

1.22.71	1.23.68

Site comparison before and after upgrade

1.22.71	1.23.68	no blocked items for comparison

Just adding new filters (Clean profile)

1. Visit a website of your choice

nytimes.com

2. Right-click on a page element of your choice
3. Select "Brave > Block element via selector"
4. Confirm the block
5. Verify that the blocked item is hidden, and remains hidden after a page refresh
6. Reopen or refresh brave://adblock and verify that a new line has been added corresponding to the newly blocked item
7. Repeat steps 1-6 at least one more time
   • Blocked NYT logo/title
   • Blocked "Subscribe" link
8. Repeat steps 1-6 for each of the following, and ensure that no new lines are created in brave://adblock:
   • closing the prompt window
   • pressing cancel on the prompt window
   • pressing OK with an empty rule in the prompt window

No blocked items	Blocked items	brave://adblock page