add version check script

script/check-versions

@@ -0,0 +1,62 @@
+#!/usr/bin/env node
+const globby = require('globby')
+const lernaConfig = require('../lerna.json')
+
+const DEP_FIELDS = [
+  'dependencies',
+  'devDependencies',
+  'peerDependencies',
+  'optionalDependencies',
+]
+
+globby(lernaConfig.packages)
+  .then(paths => {
+    return paths.reduce((packages, path) => {
+      try {
+        const pkg = require(`../${path}/package.json`)
+        pkg.path = path
+        packages.push(pkg)
+      } catch (error) {
+      }
+      return packages
+    }, [])
+  })
+  .then(packages => {
+    console.log('⏱   checking %d packages...', packages.length)
+    const map = new Map()
+    const matches = []
+    packages.forEach(pkg => map.set(pkg.name, pkg))
+    packages.forEach(pkg => {
+      DEP_FIELDS
+        .filter(field => field in pkg)
+        .forEach(field => {
+          const deps = pkg[field]
+          Object.keys(deps)
+            .filter(dep => map.has(dep))
+            .forEach(dep => {
+              const expected = map.get(dep).version
+              const actual = deps[dep]
+              if (expected !== actual) {
+                throw new Error(
+                  `${pkg.name}.${field} has bad version for ${dep}: ${expected} != ${actual}`
+                )
+              } else {
+                matches.push({
+                  from: pkg.name,
+                  to: dep,
+                  field,
+                  version: expected
+                })
+              }
+            })
+        })
+    })
+    return matches
+  })
+  .catch(error => {
+    console.error(error.message)
+    process.exit(1)
+  })
+  .then(matches => {
+    console.warn('✅   checked %d matching version dependencies', matches.length)
+  })