Enforce --output-dir with --build-command

node-src/lib/getOptions.ts

@@ -296,6 +296,12 @@ export default function getOptions(ctx: InitialContext): Options {
     throw new Error(incompatibleOptions(['--build-script-name', '--build-command']));
   }
 
+  // --build-command can put the built Storybook anywhere. Rather than reading through the value,
+  // we require `--output-dir` to avoid the issue.
+  if (potentialOptions.buildCommand && !potentialOptions.outputDir) {
+    throw new Error(dependentOption('--build-command', '--output-dir'));
+  }
+
   if (
     typeof potentialOptions.junitReport === 'string' &&
     path.extname(potentialOptions.junitReport) !== '.xml'

node-src/tasks/build.ts

@@ -43,9 +43,6 @@ export const setBuildCommand = async (ctx: Context) => {
   const buildCommand = ctx.flags.buildCommand || ctx.options.buildCommand;
 
   const buildCommandOptions = [
-    // NOTE: There is a bug in NX that outputs an invalid Storybook if the `--output-dir` flag is
-    // passed. Therefore, we need to skip that until it's fixed: https://github.com/nrwl/nx/issues/28594
-    // When that's fixed, we can remove the `!buildCommand &&` below.
     !buildCommand && `--output-dir=${ctx.sourceDir}`,
     ctx.git.changedFiles && webpackStatsSupported && `--webpack-stats-json=${ctx.sourceDir}`,
   ].filter((c): c is string => !!c);