add version related helpers

Author: RobinMalfait

packages/@tailwindcss-upgrade/src/utils/package-version.ts

@@ -1,3 +1,4 @@
+import { readFileSync } from 'node:fs'
 import fs from 'node:fs/promises'
 import { resolveJsId } from './resolve'
 
@@ -15,3 +16,14 @@ export async function getPackageVersion(pkg: string, base: string): Promise<stri
     return null
   }
 }
+
+export function getPackageVersionSync(pkg: string, base: string): string | null {
+  try {
+    let packageJson = resolveJsId(`${pkg}/package.json`, base)
+    if (!packageJson) return null
+    let { version } = JSON.parse(readFileSync(packageJson, 'utf8'))
+    return version
+  } catch {
+    return null
+  }
+}

packages/@tailwindcss-upgrade/src/utils/version.ts

@@ -0,0 +1,22 @@
+import semver from 'semver'
+import { DefaultMap } from '../../../tailwindcss/src/utils/default-map'
+import { getPackageVersionSync } from './package-version'
+
+/**
+ * Must be of major version.
+ *
+ * E.g.: `isMajor(3)`
+ */
+export function isMajor(version: number) {
+  return semver.satisfies(installedTailwindVersion(), `>=${version}.0.0 <${version + 1}.0.0`)
+}
+
+let cache = new DefaultMap((base) => {
+  let tailwindVersion = getPackageVersionSync('tailwindcss', base)
+  if (!tailwindVersion) throw new Error('Tailwind CSS is not installed')
+  return tailwindVersion
+})
+
+function installedTailwindVersion(base = process.cwd()): string {
+  return cache.get(base)
+}