Description

This pull request seeks to improve the logic of the divide function (added in #4314 / v2.13.0) to abort immediately on an attempt to divide by zero, resolving a case where it would otherwise become stuck in an infinite loop.

Additional information

Using (native) Dart Sass, trying to calculate the luminance of a value results in a division by zero (see related #4437). This was true before v2.13.0, but at least then it would result in an error. Currently, in v2.13.0, the division-by-zero causes an infinite loop to occur. The changes proposed here would reintroduce a compile error.

Example code:

@import './src/stylesheets/packages/required';

$result: luminance(color('primary'));

As of v2.12.1:

Error: Infinity or NaN toInt
     ╷
1044 │   $lum: round($lum * 1000) / 1000;
     │         ^^^^^^^^^^^^^^^^^^
     ╵
  src/stylesheets/core/_functions.scss 1044:9  luminance()
  example.scss 4:12                            root stylesheet

As of v2.13.0:

(No output due to infinite loop)

As of these changes:

Error: "Illegal division by zero"
     ╷
1020 │   @return divide(pow($x, $n), factorial($n));
     │           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     ╵
  src/stylesheets/core/_functions.scss 1020:11  exp-maclaurin()
  src/stylesheets/core/_functions.scss 1013:18  summation()
  src/stylesheets/core/_functions.scss 1024:11  exp()
  src/stylesheets/core/_functions.scss 977:13   pow()
  src/stylesheets/core/_functions.scss 1067:15  luminance()
  example.scss 4:12                             root stylesheet

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• Follow the 18F Front End Coding Style Guide and Accessibility Guide.
• Run npm test and make sure the tests for the files you have changed have passed.
• Run your code through HTML_CodeSniffer and make sure it’s error free.
• Title your pull request using this format: [Website] - [UI component]: Brief statement describing what this pull request solves.