chore: update config import error

src/config-import.js

@@ -1,6 +1,7 @@
 import yauzl from 'yauzl-promise'
 import { validate, valueSchemas } from '@mapeo/schema'
 import { json, buffer } from 'node:stream/consumers'
+import { assert } from './utils.js'
 import path from 'node:path'
 
 // Throw error if a zipfile contains more than 10,000 entries
@@ -33,13 +34,7 @@ export async function readConfig(configPath) {
     throw new Error(`Zip file contains too many entries. Max is ${MAX_ENTRIES}`)
   }
   const entries = await zip.readEntries(MAX_ENTRIES)
-  /** @type {undefined | Entry} */
-  let presetsEntry = entries.find((entry) => entry.filename === 'presets.json')
-  if (!presetsEntry) {
-    throw new Error('Zip file does not contain presets.json')
-  }
-  const presetsFile = await json(await presetsEntry.openReadStream())
-  validatePresetsFile(presetsFile)
+  const presetsFile = await findPresetsFile(entries)
 
   return {
     get warnings() {
@@ -195,6 +190,32 @@ export async function readConfig(configPath) {
   }
 }
 
+/**
+ * @param {ReadonlyArray<Entry>} entries
+ * @rejects if the presets file cannot be found or is invalid
+ * @returns {Promise<PresetsFile>}
+ */
+async function findPresetsFile(entries) {
+  const presetsEntry = entries.find(
+    (entry) => entry.filename === 'presets.json'
+  )
+  assert(presetsEntry, 'Zip file does not contain presets.json')
+
+  /** @type {unknown} */
+  let result
+  try {
+    result = await json(await presetsEntry.openReadStream())
+  } catch (err) {
+    throw new Error('Could not parse presets.json')
+  }
+
+  assert(isRecord(result), 'Invalid presets.json file')
+  const { presets, fields } = result
+  assert(isRecord(presets) && isRecord(fields), 'Invalid presets.json file')
+
+  return { presets, fields }
+}
+
 /**
  * @param {string} filename
  * @param {Buffer} buf
@@ -243,20 +264,6 @@ function parseIcon(filename, buf) {
   }
 }
 
-/**
- * @param {unknown} presetsFile
- * @returns {asserts presetsFile is PresetsFile}
- */
-function validatePresetsFile(presetsFile) {
-  if (
-    !isRecord(presetsFile) ||
-    !isRecord(presetsFile.presets) ||
-    !isRecord(presetsFile.fields)
-  ) {
-    throw new Error('Invalid presets.json file')
-  }
-}
-
 /**
  * @param {unknown} value
  * @returns {value is Record<string, unknown>}

src/utils.js

@@ -75,7 +75,7 @@ export class ExhaustivenessError extends Error {
 }
 
 /**
- * @param {boolean} condition
+ * @param {unknown} condition
  * @param {string} message
  * @returns {asserts condition}
  */

tests/config-import.js

@@ -28,10 +28,10 @@ test('config import - loading', async (t) => {
     'missing presets.json'
   )
 
-  await t.exception.all(
+  await t.exception(
     async () =>
       await readConfig('./tests/fixtures/config/invalidPresetsJSON.zip'),
-    /SyntaxError: Unexpected string in JSON/,
+    /Error: Could not parse presets.json/,
     'JSON.parse error of presets.json'
   )