WIP: address PR #475 review feedback

frontend/scripts/help-assets.test.ts

@@ -1,9 +1,10 @@
 import { mkdir, mkdtemp, rm, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import path from 'node:path'
+import { createServer } from 'vite'
 import { afterAll, afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 
-import { generateHelpAssets } from './help-assets'
+import { generateHelpAssets, helpAssets } from './help-assets'
 
 import type { ArticleMeta, HelpChange, HelpSearchEntry, HelpTitleIndex } from '@/lib/help'
 
@@ -109,4 +110,22 @@ describe ('Build-time Help assets', () => {
   it ('rejects an empty Help checkout', async () => {
     await expect (generateHelpAssets (root)).rejects.toThrow ('No Help articles found')
   })
+
+  it ('defers missing Help errors until a Help module is requested', async () => {
+    const server = await createServer ({
+	configFile: false,
+	root,
+	plugins: [helpAssets ()],
+	server: { middlewareMode: true, watch: null } })
+    try
+    {
+      await server.pluginContainer.buildStart ({})
+      await expect (server.pluginContainer.load ('\0virtual:help/articles'))
+	  .rejects.toThrow ('ENOENT')
+    }
+    finally
+    {
+      await server.close ()
+    }
+  })
 })

frontend/scripts/help-assets.ts

@@ -159,10 +159,9 @@ export const helpAssets = (): Plugin => {
       configResolved (config) {
 	state.root = path.resolve (config.root, 'help')
       },
-      async buildStart () {
-	state.data = generateHelpAssets (state.root)
-	const generated = await data ()
-	generated.files.forEach (file => this.addWatchFile (file))
+      buildStart () {
+	state.data = undefined
+	this.addWatchFile (state.root)
       },
       resolveId (id) {
 	return id.startsWith (prefix) ? `\0${ id }` : null
@@ -170,7 +169,9 @@ export const helpAssets = (): Plugin => {
       async load (id) {
 	if (!(id.startsWith (`\0${ prefix }`)))
 	  return null
-	const source = (await data ()).modules.get (id.slice (1))
+	const generated = await data ()
+	generated.files.forEach (file => this.addWatchFile (file))
+	const source = generated.modules.get (id.slice (1))
 	if (source == null)
 	  throw new Error (`Unknown Help asset: ${ id.slice (1) }`)
 	return source