fix minification issue with non-optional spaces in at-rule preludes (#198)

Author: bartveneman

README.md

@@ -58,10 +58,10 @@ The package also exports lower-level formatters for individual CSS constructs:
 
 ```js
 import {
-  format_value,
-  format_declaration,
-  format_selector,
-  format_atrule_prelude,
+	format_value,
+	format_declaration,
+	format_selector,
+	format_atrule_prelude,
 } from '@projectwallace/format-css'
 
 // Format a CSS value (e.g. the right-hand side of a declaration)

src/lib/index.ts

@@ -309,7 +309,9 @@ export function format_atrule_prelude(
 		.replace(/\)([a-zA-Z])/g, ') $1') // force whitespace between closing parenthesis and following text (usually and|or)
 		.replace(/\s*(=>|>=|<=)\s*/g, `${optional_space}$1${optional_space}`) // add optional spacing around =>, >= and <=
 		.replace(/([^<>=\s])([<>])([^<>=\s])/g, `$1${optional_space}$2${optional_space}$3`) // add spacing around < or > except when it's part of <=, >=, =>
-		.replace(/\s+/g, optional_space) // collapse multiple whitespaces into one
+		.replace(/([^<>=\s])\s+([<>])\s+([^<>=\s])/g, `$1${optional_space}$2${optional_space}$3`) // handle spaces around < or > when they already have surrounding whitespace
+		.replace(/\s+/g, SPACE) // collapse multiple whitespaces into one
+		.replace(/([:,]) /g, minify ? '$1' : '$1 ') // in minify mode, remove optional spaces after : and ,
 		.replace(
 			/calc\(\s*([^()+\-*/]+)\s*([*/+-])\s*([^()+\-*/]+)\s*\)/g,
 			(_, left, operator, right) => {

test/atrules.test.ts

@@ -367,6 +367,12 @@ test('minify: new-fangled comparators (width > 1000px)', () => {
 	expect(actual).toEqual(expected)
 })
 
+test('minify: keeps necessary whitespace between keywords', () => {
+	let actual = minify(`@media screen or print {}`)
+	let expected = `@media screen or print{}`
+	expect(actual).toEqual(expected)
+})
+
 test.skip('preserves comments', () => {
 	let actual = format(`
 		@media /* comment */ all {}