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chore: use u flag for regexes #12249

merged 1 commit into from Feb 5, 2022

chore: use u flag for regexes #12249

merged 1 commit into from Feb 5, 2022


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Usage of the u flag with regular expressions is recommended.

The u flag has two effects:

It enables correct handling of UTF-16 surrogate pairs.
It ensures the correct behavior of regex character ranges.

/^[πŸ‘]$/.test("πŸ‘") //β†’ false
/^[πŸ‘]$/u.test("πŸ‘") //β†’ true

Make the regular expression throwing syntax errors early as disabling JavaScript specification Annex B[1] extensions.

Because of historical reason, JavaScript regular expressions are tolerant of syntax errors. For example, /\w{1, 2/ is a syntax error, but JavaScript doesn't throw the error. It matches strings such as "a{1, 2" instead. Such a recovering logic is defined in Annex B of Javascript specification.

The u flag disables the recovering logic Annex B of the Javascript specification. As a result, you can find errors early. This is similar to the strict mode.

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Codecov Report

Merging #12249 (7031c68) into main (4f4be57) will not change coverage.
The diff coverage is 100.00%.

Impacted file tree graph

@@           Coverage Diff           @@
##             main   #12249   +/-   ##
  Coverage   67.52%   67.52%           
  Files         328      328           
  Lines       17244    17244           
  Branches     5069     5069           
  Hits        11644    11644           
  Misses       5567     5567           
  Partials       33       33           
Impacted Files Coverage Ξ”
packages/jest-reporters/src/utils.ts 81.25% <100.00%> (ΓΈ)

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@SimenB SimenB left a comment

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cool, thanks!

@SimenB SimenB changed the title Fix:Added u flag for regex chore: use u flag for regexes Feb 5, 2022
@SimenB SimenB merged commit f3390fe into jestjs:main Feb 5, 2022
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4 participants