fix: DbDelegationsStorage#find throws UnexpectedDelegation w/ { row }…

… if failed bytesToDelegations (#476)

Motivation:
* aid in debugging #471 
* hope this
* confirms that this error is coming from `DbDelegationsStorage#find` (I
see '.find' in the hard-to-read sentry stack trace)
* gives insight into what the db row is like (esp `row.bytes`) that
can't be parsed

packages/access-api/src/models/delegations.js

@@ -18,6 +18,8 @@ import {
  * @typedef {import("../types/database").Database<Tables>} DelegationsDatabase
  */
 
+export const delegationsTable = /** @type {const} */ ('delegations_v2')
+
 /**
  * DelegationsStorage that persists using SQL.
  * * should work with cloudflare D1
@@ -26,7 +28,7 @@ export class DbDelegationsStorage {
   /** @type {DelegationsDatabase} */
   #db
   #tables = {
-    delegations: /** @type {const} */ ('delegations_v2'),
+    delegations: delegationsTable,
   }
 
   /**
@@ -105,12 +107,41 @@ export class DbDelegationsStorage {
   }
 }
 
+/**
+ * indicates that processing failed due to encountering an unexpected delegation.
+ * e.g. if a delegation could not be parsed from underlying storage
+ */
+class UnexpectedDelegation extends Error {
+  name = 'UnexpectedDelegation'
+}
+
 /**
  * @param {Pick<DelegationRow, 'bytes'>} row
  * @returns {Ucanto.Delegation}
  */
 function rowToDelegation(row) {
-  const delegations = bytesToDelegations(row.bytes)
+  /** @type {Ucanto.Delegation[]} */
+  let delegations = []
+  try {
+    delegations = bytesToDelegations(row.bytes)
+  } catch (error) {
+    if (
+      typeof error === 'object' &&
+      error &&
+      error.toString() === 'TypeError: Input should be a non-empty Uint8Array.'
+    ) {
+      throw Object.assign(
+        new UnexpectedDelegation(`failed to create delegation from row`, {
+          cause: error,
+        }),
+        // adding these so they appear in sentry et al and can aid debugging
+        {
+          row,
+        }
+      )
+    }
+    throw error
+  }
   if (delegations.length !== 1) {
     throw new Error(
       `unexpected number of delegations from bytes: ${delegations.length}`
@@ -123,7 +154,7 @@ function rowToDelegation(row) {
  * @param {Ucanto.Delegation} d
  * @returns {DelegationRowUpdate}
  */
-function createDelegationRowUpdate(d) {
+export function createDelegationRowUpdate(d) {
   return {
     cid: d.cid.toV1().toString(),
     audience: d.audience.did(),

packages/access-api/test/delegations-storage.test.js

@@ -1,5 +1,9 @@
 import { context } from './helpers/context.js'
-import { DbDelegationsStorage } from '../src/models/delegations.js'
+import {
+  createDelegationRowUpdate,
+  DbDelegationsStorage,
+  delegationsTable,
+} from '../src/models/delegations.js'
 import { createD1Database } from '../src/utils/d1.js'
 import * as assert from 'node:assert'
 import { createSampleDelegation } from '../src/utils/ucan.js'
@@ -65,6 +69,44 @@ describe('DbDelegationsStorage', () => {
     )
     assert.deepEqual(carolDelegations.length, 0)
   })
+
+  it('find throws UnexpectedDelegation when encountering row with empty bytes', async () => {
+    const { d1, issuer } = await context()
+    const db = createD1Database(d1)
+    const delegations = new DbDelegationsStorage(db)
+    const row = createDelegationRowUpdate(
+      await ucanto.delegate({
+        issuer,
+        audience: issuer,
+        capabilities: [{ can: '*', with: 'ucan:*' }],
+      })
+    )
+    // insert row with empty bytes
+    await db
+      .insertInto(delegationsTable)
+      .values([
+        {
+          ...row,
+          bytes: Uint8Array.from([]),
+        },
+      ])
+      .onConflict((oc) => oc.column('cid').doNothing())
+      .execute()
+    // now try to find
+    const find = () => collect(delegations.find({ audience: issuer.did() }))
+    let findError
+    try {
+      await find()
+    } catch (error) {
+      findError = error
+    }
+    assert.ok(findError && typeof findError === 'object')
+    assert.deepEqual(
+      'name' in findError && findError?.name,
+      'UnexpectedDelegation'
+    )
+    assert.ok('row' in findError, 'UnexpectedDelegation error contains row')
+  })
 })
 
 /**