UIP-2303 getSelectionStart Util for CTE Cursor Caching

[kaanaksoy-wk]

Ultimate Problem

In order to implement cursor index caching in CTEs, we need a streamlined function that gives us the selectionStart value for any input type.

The getSelectionStart function in this PR handles inconsistent behavior across browsers—Chrome does not support selectionStart for number and email inputs—while also properly handling text areas.

Solution

• Create a getSelectionStart function similar to the already existing setSelectionRange utility.
• Write tests to verify the functionality of the getSelectionStart utility.

Testing Suggestions

• Verify that tests pass.

Possible Areas of Regression

• N/A

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FYA: @aaronlademann-wf @greglittlefield-wf @clairesarsam-wf @joelleibow-wf @jacehensley-wf

[aviary2-wf]

Raven

Number of Findings: 0

[codecov-io]

Codecov Report

Merging #69 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #69      +/-   ##
=========================================
+ Coverage   97.69%   97.7%   +0.02%     
=========================================
  Files          28      28              
  Lines        1380    1387       +7     
=========================================
+ Hits         1348    1355       +7     
  Misses         32      32

[clairesarsam-wf]

See the Dartlang style guide here. This comment would be more compliant as something like:

Returns the index of the first selected character in [input].

To workaround this chrome bug, returns null for [EmailInputElement] or [NumberInputElement] on Chrome. null will also be returned for any [input] that does not support selectionStart.

[clairesarsam-wf]

a type of InputElement may be more appropriate here instead of Element

[kaanaksoy-wk]

The reason I used Element here is because, from what I understand, TextAreaElement does not inherit from InputElement, but we still want to support it in this function. It is the same reason why setSelectionRange also accepts an Element as its parameter.

[clairesarsam-wf]

Oh, right, that's an annoying quirk. Looks good then!

[clairesarsam-wf]

I think these tests are better suited to separate groups - although they're related methods, the test descriptions aren't as clear as they could be and separated tests would be more atomic/unit-ish. So something that looks like:

group('setSelectionRange', () {
  test('throws an ArgumentError if called on an unsupported Element type', () {
    ...
  });
  ...
});

group('getSelectionStart', () {
  test('returns normally if called on an unsupported Element type', () {
    ...
  });
  ...
});

[clairesarsam-wf]

@kaanaksoy-wk Will +1 once test failures are resolved

[clairesarsam-wf]

+1

[greglittlefield-wf]

I'm going to make this a separate ticket as a subtask of the main ticket, so that the main one can be used for the Web Skin Dart PR.

[greglittlefield-wf]

• Code looks good
• Test pass in when run locally in both content-shell and Chrome (besides one unrelated failure fixed here: UIP-2304 Don't run ValidationUtil-related tests in dart2js #70)

+10

[leviwith-wf]

QA +10

• Testing instruction
• Dev +1's
• Dev/QA +10
• Unit tests created/updated
• All unit tests pass
• Rosie ran/Rosie comment displays expected info
• Dependency Scan Clean

Merging.