fix: put plugin-only tailwind classes in core's utilities layer, SDK 1.0.4

packages/plugin-sdk/cli/lib/css-classes.mjs

@@ -0,0 +1,35 @@
+/**
+ * The class names a stylesheet has rules for, unescaped, so `.md\:w-44`
+ * reads as the candidate `md:w-44` a plugin writes.
+ */
+export function classNamesInCss(css) {
+  const names = new Set();
+  // Declarations hold numbers like 0.25rem, so only selectors are read.
+  const selectors = css.replace(/\{[^{}]*\}/g, "{}");
+  for (const match of selectors.matchAll(
+    /\.((?:\\[0-9a-fA-F]{1,6} ?|\\.|[\w-])+)/g,
+  )) {
+    names.add(
+      match[1].replace(/\\([0-9a-fA-F]{1,6}) ?|\\(.)/g, (_all, hex, char) =>
+        hex ? String.fromCodePoint(parseInt(hex, 16)) : char,
+      ),
+    );
+  }
+  return names;
+}
+
+/**
+ * Splits a plugin's candidates by whether core's own CSS already has them.
+ * A class core ships keeps the plugin's copy below core's utilities, so it can
+ * never reorder core's rules. Any other class has no rule in core to fight,
+ * so it goes in core's utilities layer and overrides the way it would in one
+ * Tailwind build.
+ */
+export function splitByCoreClasses(candidates, coreClasses) {
+  const shared = [];
+  const own = [];
+  for (const candidate of candidates) {
+    (coreClasses.has(candidate) ? shared : own).push(candidate);
+  }
+  return { shared, own };
+}