New: Support content-only builds via outputDir option

When outputDir is passed and the directory already exists, the build
skips framework source copy and CLI compilation, writing only course
content JSON and assets. This enables multilang to run a single full
build for the default language and content-only builds for the rest.

Author: taylortom

lib/AdaptFrameworkBuild.js

@@ -40,11 +40,12 @@ class AdaptFrameworkBuild {
    * @property {String} userId The user executing the build
    * @property {String} expiresAt When the build expires
    * @property {Boolean} compress Whether output files should be compressed into an archive file
+   * @property {String} outputDir If set, uses this as the build root. If the directory already exists, only content data and assets are written (framework copy and compilation are skipped)
    *
    * @constructor
    * @param {AdaptFrameworkBuildOptions} options
    */
-  constructor ({ action, courseId, userId, expiresAt, compress }) {
+  constructor ({ action, courseId, userId, expiresAt, compress, outputDir }) {
     /**
      * The MongoDB collection name
      * @type {String}
@@ -150,6 +151,11 @@ class AdaptFrameworkBuild {
       * @type {Hook}
       */
     this.postBuildHook = new Hook({ mutable: true })
+    /**
+     * Custom output directory. If the directory already exists, only content and assets are written
+     * @type {String}
+     */
+    this.outputDir = outputDir ?? null
   }
 
   /**
@@ -164,39 +170,50 @@ class AdaptFrameworkBuild {
     if (!this.expiresAt) {
       this.expiresAt = await AdaptFrameworkBuild.getBuildExpiry()
     }
-    // random suffix to account for parallel builds executed at exactly the same millisecond
-    const randomSuffix = `_${Math.floor(Math.random() * 1000).toString().padStart(4, '0')}`
-    this.dir = path.resolve(framework.getConfig('buildDir'), Date.now() + randomSuffix)
+    if (this.outputDir) {
+      this.dir = this.outputDir
+    } else {
+      // random suffix to account for parallel builds executed at exactly the same millisecond
+      const randomSuffix = `_${Math.floor(Math.random() * 1000).toString().padStart(4, '0')}`
+      this.dir = path.resolve(framework.getConfig('buildDir'), Date.now() + randomSuffix)
+    }
     this.buildDir = path.join(this.dir, 'build')
     this.courseDir = path.join(this.buildDir, 'course')
 
+    const dirExists = await fs.access(this.dir).then(() => true, () => false)
+    const contentOnly = this.outputDir && dirExists
+
     const cacheDir = path.join(framework.getConfig('buildDir'), 'cache')
 
     await ensureDir(this.dir)
     await ensureDir(this.buildDir)
-    await ensureDir(cacheDir)
+    if (!contentOnly) {
+      await ensureDir(cacheDir)
+    }
 
     logDir('dir', this.dir)
     logDir('buildDir', this.buildDir)
     logDir('cacheDir', this.cacheDir)
 
     await this.loadCourseData()
 
-    await Promise.all([
-      this.copyAssets(),
-      copyFrameworkSource({
+    const tasks = [this.copyAssets()]
+    if (!contentOnly) {
+      tasks.push(copyFrameworkSource({
         destDir: this.dir,
         enabledPlugins: this.enabledPlugins.map(p => p.name),
         linkNodeModules: !this.isExport
-      })
-    ])
+      }))
+    }
+    await Promise.all(tasks)
+
     await this.preBuildHook.invoke(this)
 
     await this.writeContentJson()
 
     logDir('courseDir', this.courseDir)
 
-    if (!this.isExport) {
+    if (!contentOnly && !this.isExport) {
       try {
         logMemory()
         await AdaptCli.buildCourse({