fix future sort order bug

When sorting based on the BigInt values, we are doing `Number(a - z)`,
but if the result of `a - z` is bigger then the max number, then
overflows would happen. This will result in a hard-to-debug bug.

This is a prevention for the future, because currently all our `a - z`
values will not reach Number.MAX_SAFE_INTEGER mark (9007199254740991).

Author: RobinMalfait

src/index.js

@@ -26,6 +26,18 @@ let env = {
   DEBUG: process.env.DEBUG !== undefined,
 }
 
+function sign(bigIntValue) {
+  if (bigIntValue === 0n) {
+    return 0
+  }
+
+  if (bigIntValue > 0n) {
+    return 1
+  }
+
+  return -1
+}
+
 // ---
 
 // This is used to trigger rebuilds. Just updating the timestamp
@@ -262,7 +274,7 @@ function generateRules(tailwindConfig, candidates, context) {
 
 function buildStylesheet(rules, context) {
   let sortedRules = rules.sort(([a], [z]) => {
-    return Math.sign(Number(a - z))
+    return sign(a - z)
   })
 
   let returnValue = {
@@ -1132,7 +1144,7 @@ module.exports = (pluginOptions = {}) => {
                 }
 
                 // Inject the rules, sorted, correctly
-                for (let [sort, sibling] of siblings.sort(([a], [z]) => Math.sign(Number(z - a)))) {
+                for (let [sort, sibling] of siblings.sort(([a], [z]) => sign(z - a))) {
                   // `apply.parent` is refering to the node at `.abc` in: .abc { @apply mt-2 }
                   apply.parent.after(sibling)
                 }