do not error if frontmatter includes next GHES release or hardcoded next

lib/enterprise-server-releases.js

@@ -4,6 +4,9 @@ const versionSatisfiesRange = require('./version-satisfies-range')
 // enterprise-releases/docs/supported-versions.md#release-lifecycle-dates
 const dates = require('../lib/enterprise-dates.json')
 
+// Some frontmatter may contain the upcoming GHES release number
+const next = '3.1'
+
 const supported = [
   '3.0',
   '2.22',
@@ -57,6 +60,7 @@ const deprecatedReleasesWithNewFormat = deprecated.filter(version => versionSati
 const deprecatedReleasesOnDeveloperSite = deprecated.filter(version => versionSatisfiesRange(version, '<=2.16'))
 
 module.exports = {
+  next,
   supported,
   deprecated,
   legacyAssetVersions,

lib/get-applicable-versions.js

@@ -1,4 +1,5 @@
 const allVersions = require('./all-versions')
+const { next } = require('./enterprise-server-releases')
 const versionSatisfiesRange = require('./version-satisfies-range')
 
 // return an array of versions that an article's product versions encompasses
@@ -15,6 +16,8 @@ function getApplicableVersions (frontmatterVersions, filepath) {
   // get an array like: [ 'free-pro-team@latest', 'enterprise-server@2.21', 'enterprise-cloud@latest' ]
   const applicableVersions = []
 
+  let nextVersion = false
+
   // where frontmatter is something like:
   //   free-pro-team: '*'
   //   enterprise-server: '>=2.19'
@@ -23,6 +26,15 @@ function getApplicableVersions (frontmatterVersions, filepath) {
   // ^ where each key corresponds to a plan
   Object.entries(frontmatterVersions)
     .forEach(([plan, planValue]) => {
+      // Special handling for frontmatter that evalues to the next GHES release number or a hardcoded `next`:
+      // we don't want to return it in the applicable versions array or it will become a permalink,
+      // but we also don't want to throw an error if no other versions are found.
+      if (planValue !== '*') {
+        if (versionSatisfiesRange(next, planValue) || planValue === 'next') {
+          nextVersion = true
+        }
+      }
+
       // for each plan (e.g., enterprise-server), get matching versions from allVersions object
       const relevantVersions = Object.values(allVersions).filter(v => v.plan === plan)
 
@@ -42,7 +54,7 @@ function getApplicableVersions (frontmatterVersions, filepath) {
       })
     })
 
-  if (!applicableVersions.length) {
+  if (!applicableVersions.length && !nextVersion) {
     throw new Error(`No applicable versions found for ${filepath}. Please double-check the page's \`versions\` frontmatter.`)
   }